ASK THE MXPERTS: YZ250 PINGING, TEXAS NATIONAL, KX450F FOOTPEGS, RM250 VERSUS YZ250: DRAG TIMES & MORE

2006 YZ250F: HANDLEBARS HEIGHT
Dear MXA,
    My son and nephew recently got the new motocross bikes and the bug bit me hard! After 25 years away from dirt bikes, I purchased a 2006 Yamaha YZ250F. In your test of this bike it was recommended to raise the handlebars by 10mm. Can you please recommend where I might purchase new mounts for my stock clamps?

   The easiest way to get the taller handlebars is with taller handlebars. Every bar manufacturer makes a "YZ-high" bar and, amazingly, taller bars cost about the same as taller bar mounts.  We used ProTaper "YZ-High" bars. The stock YZ-F bars are 80mm high with a 50mm sweepyou can compare handlebars charts from Tag, Renthal, Azonic and ProTaper to find any bar that is 8 to 10mm higher. The 2007 Yamaha's will have taller bars.

SUZUKI RM-Z450: WHITE PLASTIC
Dear MXA,
    I want to white my RM-Z450 out like Nick Wey's CRF450. I have an all white plastic kit but there are no all white graphics for my bike. Do you have any suggestions?

   We've had the same problem, but the solution is simple. We find the style of graphics that we like and we cut, with scissors or X-acto knife, the color elements that we want.

    Graphics are kind of weird in that the use the same color of 3 mil vinyl to cover plastic of the same color. One Industries RM-Z450 TechnoFlex Graphics have a reasonable amount of white and only a little bit of yellow. Go to www.oneindustries.com to look that them.

WORKS BIKE VERSUS PRACTICE BIKE
Dear MXA,
    What is the difference between a factory rider's practice bike and their race bike?

   Every race team is different, but normally a factory rider has three different types of bike:

    (1) Race bike: This bike is used only at races. It is pampered and cared for during its whole life cyclewhich is approximately four to five races for a factory rider.

    (2) Test bike: Each team will have various bikes that are used for testing. They are identical to the race bike except for the fact that they are used during the weekdays to test various performance products and ideas at the test tracks. The test bikes swing back and forth between being in perfect condition and being well used. Test bikes do get overhauled constantlyso while they are well usedthey are mechanical perfect. They could be raced in a pinch and are sometimes used for races like the Prequel. When the test bikes starts to show its age it can get demoted to a dyno bikewhere it is used in the shop to test head mods, pistons and pipes.

    (3) Practice bikes: A practice bike has the suspension and engine mods of the race bikebut leads a hard life (normally cared for by the rider and his helpers) it doesn't get the loving care of the race bike. The rider's mechanic will keep it running, but with most factory riders living for states without income tax (Florida and Texas), the in-house factory mechanics normally only work on the bike occasionallyleaving the rider on his own for longer periods of time. Practice bikes get thrashed very quickly.

2005 YZ250: FRATERNAL TWINS
Dear MXA,  
    In the article on race mods for the 2006 YZ250, did you perform the exact same mods on the 2005 model, which is what I have?

   Yes, with the exception of the SSS suspension, the 2006 YZ250 is virtually identical to the 2005 in terms of mods.

YAMAHA YZ250F: GOING FLAT ON TOP
Dear MXA,
    I race at tracks around Phoenix, so it is close to MXA's SoCal tracks.  My YZ250F feels like it goes flat at high rpm.  It is all stock except for accelerator pump. Can you help me fix it?

   As you have already discovered four-stroke jetting issues, while minor in comparison to some two-strokes are much harder to diagnose (and when it comes to changing a jet they are a nightmare to work on).

    First off, Jetting-wise we don't think you will find any major differences by making changes. We can suggest four approaches, but they are theoretical in some aspects.

    (1) Occasionally we change the pilot jet...going slightly larger in warm air and a lot larger in the winter (cold air).

    (2) You can try a bigger main, but we called Doug Dubach, Yamaha's test rider, with your question and he said that in rare instances a main jet might help, but that the YZ250F tends to rev fairly high while feeling flat in the upper end. He said that it is part of the engine's nature. He wondered if you were coming from another brand, which might have been crisper on top which makes you more sensitive to the feel of the YZ250F.

    (3) The quickest fix is an aftermarket pipewhich picks up the rev on top and fills in the gaps.

    (4) Although the pilot jet change doesn't really affect the top-end, sometimes a richer pilot and the perfect fuel screw setting, make the engine quicker across the middle and able to carry farther in the top. So you fix a problem at one end, by maximizing the other.

HONDA CRF250: BURNING OIL
Dear MXA,
    Recently after racing a 3-hour hare scramble, I noticed that my oil height in my CRF250 dropped more than usual after a race. It was maybe 1/8" lower than normal on the dipstick. This track was a very sandy, fast and high rpm track. Would this be a reason for the reduced oil height or is there another reason?

   Many four-stroke riders don't realize that their bikes burn oil in much the same way as a two-stroke. You lose a little when starting the bike, some blows by the rings and some is lost to normal wear and tear.

    It doesn't seem unusual to use a considerable amount of oil on a CRF250 in a three-hour race. The addition of sand and high rpm running is obviously a contributing factor. Just the fact that the race was three hours long meant that your rings were three hours older at the end of the event than they were at the beginning.

    If you don't see smoke, the overflow tube isn't blowing oil into the airbox and the crank seals aren't leakingwe would assume that your oil loss is natural for the event you raced.

    The key element is that you check the oil and keep track of itmany CRF250s have fallen victim to rider's who don't want to take the time to look at the dip stick. Unfortunately, a sight glass would be a worthwhile addition to a CRF250, but Honda claimed that there wasn't enough room on the CRF250 cases.

2006 YZ450F: POPS AND BOGS
Dear MXA.
    My 2006 YZ450F pops at low rpm, when decelerating with the throttle off and it doesn't want to idle. Also, it won't start without choke even when warm. Have you guys experienced something similar with this model?

   Your problem is not uncommon and the fix is relatively simple. The standard pilot is 42. We have had luck fixing this problem with a 45, 48 or 50 pilot jet. The choice depends on how severe the problem is (you be the judge). We would start with a 48, since summer is coming, but order a 50 pilot for winter.


YZ125: PAGING FOR RICK PETERSON
Dear MXA,
    I Hope you can help. I read an article in an old MXA about an RPMS big-bore kits for the YZ125. Could you please let me know the e-mail address for them. I contacted them last year, but I have since changed computers without keeping my favourite links. I want the 134cc kit.

   You can find out about Rick Peterson's big-bore engine kits at www.maxrpms.com or (608) 224-2524


SPEED VERSUS OLN: BETTER OR WORSE
Dear MXA,
    Do you know if Speed is showing the AMA outdoor Nationals? I know they showed every Supercross. I hope they cover the Nationals as well.

   The AMA Nationals will be shown on OLN (the Tour de France channel) on a week delay--and a longer delay during the Tour.

BRAKE FLUID: KILLING ME WITH KINDNESS
Dear MXA,
    When dealing with brake fluid, I have always been told that the higher the "DOT" number, the higher the quality, boiling point, resistance to moisture, etc.  Based on this theory, DOT 5 (or in this case, Motorex DOT 5.1) should be superior to the DOT 4 that is recommended for my CRF450R. However, it seems like I read in your magazine somewhere that you should never use DOT 5 Brake Fluid - can you clarify this for me?

   We're not sure how detailed you want to get. Suffice it to say that we recommend either DOT 4 or DOT 5.1. If you accept that answer, don't read any furtherbecause from here on it gets boring. You can expect your motorcycle to be floored with low-cost DOT 3 fluid. It is best to replace it after break-in with a racing DOT 3, 4 or 5.1 fluid (preferably with one that carries the highest dry boiling point you can find).

    In almost all cases DOT 3 is the least expensive and lowest performing brake fluid produced. The exception to this rule is Maxima DOT 3 550 with a 568 dry boiling point (the highest of any stateside-produced motorcycle brake fluid).
    Base: Synthetic Polyglycol base.
    Dry boiling point: Minimum required dry boiling point-401 degrees.     
    Wet boiling point: Minimum required wet boiling point-284 degrees.
    Viscosity: Viscosity at minus 40 degrees-1500 cst.
    Compatibility: DOT 4 & 5.1.

    Most DOT 3 fluids meet DOT 4 regulations and vice versa (save Motul's Racing Brake Fluid 600, which has incredibly high dry and wet boiling points of 585 and 421 degrees). Motul 600 exceeds DOT 3's 1500 cst viscosity rating by two percent (at minus 40 degrees) to be labeled as such.
    Base: Synthetic Polyglycol base.
    Dry boiling point: Minimum required dry boiling point-446 degrees.
    Wet boiling point: Minimum required wet boiling point-311 degrees.
    Viscosity: Viscosity at minus forty degrees-1800 cst.
    Compatibility: DOT 3 & 5.1.
 
    The high boiling points of DOT 5  made DOT 5 the hottest fluid going in the late 80s (now only Harley-Davidson spec's it). But the fluid's syrupy nature wreaked havoc on the system if water or air entered. Since thick brake fluid won't allow microbubbles to float to the top of the reservoir, unwanted air is dispersed throughout the system (making lever action mushy). Unlike a Polyglycol fluid, silicone-based brake fluids do not absorb water. Instead, the heavier water settles toward the bottom of the hydraulics, where the caliper resides. That means a liquid with a low boiling point is residing in the area that generates the most heat. If not bled, the caliper can also corrode.
    Base: Silicone base. DOT 5 is purple. The purple color is a DOT mandate indicating a silicone base that cannot be mixed with the yellowish DOT 3, DOT 4 or DOT 5.1 fluids. When mixed, the fluids coagulate and turn to Jell-O. Unlike DOT 3, DOT 4 and DOT 5.1, DOT 5 will not damage painted surfaces.
    Dry boiling point: Minimum required dry boiling point-500 degrees.
    Wet boiling point: Minimum required wet boiling point-500 degrees.
    Viscosity: Viscosity at minus forty degrees-900 cst.
    Compatibility: DOT 5 silicone base

   DOT 5.1 is a European-produced fluid came into existence due to the fast moving, anti-lock braking systems (ABS) used on today's automobiles. DOT 5.1 is the thinnest fluid and offers the least hot-to-cold change in viscosity. This fluid has the highest wet boiling point of any of the synthetic Polyglycol.
    Base: Synthetic Polyglycol base.
    Dry boiling point: Minimum required dry boiling point-500 degrees.
    Wet boiling point: Minimum required wet boiling point-356 degrees.
    Viscosity: Viscosity at minus forty degrees-900 cst.
    Compatibility: DOT 3 & DOT 4.



2006 KTM 525SXF: FUTURE TEST RIDER
Dear MXA,
    I'm coming from 2006 CRF450 with a resprung/revalved MB1 set up, Ti shock spring, oil lock collars, works bladder and cap, etc. to an MX Tech revalved/resprung 2006 KTM 525SX. Mike Battista's work was excellent. Plush, able to ride effortlessly through chop, and coming up short was no problem. With my WP stuff, I can't say the same. I've tried the sag from 105 to 115.  Played with HSC, LSC, compression, rebound, etc. I got the bike to where I can ride it reasonably fast, but I don't have 100% confidence in it. On more technical stuff the chassis seems to flex and be a little more active than my CRF. The front end seems to understeer a bit on corner exits. Overall the bike just seems less forgiving than my Honda and reacts more to sudden hits or rider mistakes. My question is, are these more of a KTM tendency or can you offer me some baselines to get it a little more forgiving on the big hits?

   You have the makings of a test rider. In truth your evaluation of the differences between a Honda CRF and KTM is very accurate. The problem is that your assessment is so spot-on that you have discovered the inherent shortcomings of KTM's overall designshortcomings that are hard to iron out.

    When KTM's suspension is set-up for hard, fast hits (so that it won't bottom or bang) it is wallowy over the small stuff. When you get it dialed in for chatter bumps and the rolling stuff, it rockets through the stroke on the big stuff. Such is the life with KTM's current rising rate. Worst of all, KTM's don't like low-speed, high-load G-outs. By that we are talking about slow shock shaft speeds, with considerable downward weight on the suspension (like dropping into a corner from a hump in first or second gear). Nothing can stock the WP shock from bottoming out at slow shock shaft speedsit is a rising rate deficiency. There is no comfort in knowing that the 2006 bikes are much better than older KTM's in these areas.

    The KTM chassis does flexthis is most noticeable on the entrance to turns when either the chassis pendulums back and forth when the front tire is planted or the front end see-saws when the rear wheel is planted. We call this clanking (and the CRF450 is not immune to clanking at the entrance of turns, but there's was a geometry problem). KTM•s clank is caused by a combination of frame flex and slack geometry. Next year's KTM will have a much stiffer steel frame.

    All KTM's understeer from the center outwe like to call this "Euro Handling." The 525 doesn't push worse, but because of its big-bore engine and added torque it should because the engine tends to chug the chassis into the turn instead of around it.

    We can't really help you with baseline settings for an MX Tech shock because it will be much different than the stock stuff. We know that we haven't offered you any help, but we are impressed with your evaluation of your problem.


MOTOR MOUTH VERSUS ENGINE MOUTH
Dear MXA,
    As I spend the next year in Iraq, Motocross Action Magazine is my fix to ease my motocross addiction. Aside from my family, the riding and tinkering on the bikes is what I miss the most over here. With 3 boys and a wife that rides, there is always work to be done on the bikes, so the "Ask the MXperts" is the section I read after I finish "Jody's Box." I had to smile when I saw the "Engine vs Motor" question in the May 2006 "Ask the MXperts." It was a flash back to my powerplants instructor in college. He held a Ph.D. in electrical engineering, and made a habit of driving home the difference between the two.  That lesson served me well for many years flying for the Navy and then the airlines. Now, while relaxing and reading about my favorite hobby, I'm reminded once more. It is a small point, but it just showcases the knowledge that MXA is able to share in an entertaining way. Thanks for helping pass the time over here, keep up the great work.

  Thanks for your letter. We, like you, have always been sticklers about the difference between an engine and motoryet the word still manages to make it into the magazine on occasion (and every other magazine constantly). Your letter was one a several on the subject, but most started with the phrase "Well, why is called a motorcycle and not an enginecycle?"

HONDA XR200: JUST THE FACTS
Dear MXA,
    I have a Honda XR200 dual bike, which has a 4-stroke engine with a displacement of 200cc. It's listed as having an output of 19 horsepower. I have the following questions:
    1. Why is there a huge gap between the hp produced by this bike and bikes like the CRF250 and CR250?
    2. What is the difference between motocross biking and off-road biking?
    3. What are the differences between motocross bikes and off-road bikes in terms of design and performance?

   The huge gap in horsepower is the product of the extra 50cc, higher compression and Honda's intent. Honda did not intend for the XR200 to be raced. They focused on reliability and cost issues instead of horsepower and a $6000 price tag. The XR200 is a trail bike. It was built to last for years and one of the easiest ways to increase longevity is to decrease horsepower. Motocross bikes are full-race machinesalthough they will last an acceptable amount of timethey wear out much faster than a trail bike.

    The difference between off-road riding and motocross is that MX is an all-out race. The riders go as hard as humanly possible and stress their machines to the fullest. The course is especially built to be very challenging. Off-road riding takes place over natural terrain, for longer distances and with lower intensity. An off-road rider does not face man-made obstaclesnor can he go ten-tenths over terrain that he is unfamiliar with.

    A motocross bike has very stiff suspension, powerful (and sometimes harder to use) engine output and an emphasis on light weight. Off-road bikes have much softer suspension, easier to use (and broader) powerbands. Off-road bikes tend to be heavier and are often equipped with rudimentary lights, lighting coils, kickstands and larger gas tanks.


2005 CRF250: CLOSING THE BIG GAP
Dear MXA,
    I have a 2005 CRF 250R and want to know what the best gearing is for MX tracks? Right now I'm using a 13/50. I heard Hondas have a big gap between second and third and the only way to fix it, if your not on a factory team, is to change the gearing.    

   As a rule of thumb we automatically suggest adding a tooth to the rear sprocket of the 2005 CRF250. On hard dirt the stock gearing is passable, but once you hit deep loam the engine will be reluctant to make the second-to-third upshift without falling off the pipe. Going to a 52-tooth rear sprocket will bring third gear closer to the meat of the motor.

    There is paradoxically a different school of thought that says you should opt for a 50 (one tooth less). We actually ran a 50 in 2004 because it allowed us to use second longer so that we didn't have to shift to third on the exitwhere it tended to go flat. With some modest power increases in 2005 and 2006, we have given up on the 50 in favor of the 52, which punches up the bottom end, brings third gear closer to second and improves throttle response.

IN SEARCH OF ICAT
Dear MXA,
    I have been reading about the iCat. What is the deal with it and does it actually work by creating a more efficient burn?

   We have tested the iCat, but our experience is limited to the bikes we tried it on. An iCat doesn't increase the voltage, instead it spreads the duration of the spark out. All modern CDI-equipped ignitions produce more than enough voltage to ignite the fuel/air mixture, but according to the iCat designers--the spark doesn't last long enough. The stock discharge voltage is high, but only last about 10 nanoseconds. The short duration of the electrical discharge means that some fuel is left unburned or, at the very least, the combustion is not simultaneous enough to maximize power. Energy is lost when partially unburned fuel is passed into the exhaust system as noxious gases. The iCat electrically alters the shape, speed and profile of the spark to make it last longer.

    The iCat is not a capacitor-style spark boosters, like the old Roost Boost. We never like Roost Boost because of the lag between ignition timing and capacitor buildup.

    We tested the iCat on two bikes (back in 2004) a YZ250 and CR125. On the YZ250 it gave the impression of crisper jetting and better throttle response (but not impressively so), while on the Honda CR125 it invigorated the complete powerband (impressively so). We would surmise that good powerbands don't benefit as much as bad ones (thus the ecstatic response on the CR125). The iCat reps also told us that the iCat didn't do anything for the 2004 RM125.

    We haven't tested it since 2004and since you didn't say what kind of bike you were putting it on (in addition to our mixed results with the bikes we tried), we can't give you a definitive answer.


2005 YZ250F: SPROCKET SIZE
Dear MXA,
    What size sprocket did you find the best for a 2005 YZ250F? I read that you like a tooth higher on the 2002, what about the 2005?  

   We left the 2004 and 2005 gearing stock. The YZ250F has gained some power since 2002 and with more power we didn't feel the need to gear it down for most tracks. Of course, tighter tracks wouldn't be hurt by one tooth on the rear to help it get out of corners with a little more authority.


CANNONDALE DEFENDER
Dear MXA,
    What cave has MXA been living in? In the Fuel Injection article in the June 2006 issue you said, "but that is only because it doesn't (fuel injection) come stock on any bike." What you meant to say is that is does not come on any of the big four yet and that Cannondale was the FIRST! And that was done 4 or 5 years ago, way ahead of any of the others. But it is painfully obvious that the Cannondale will never rate any print or have done anything first in your eyes since a big check is not associated with it. If this bike has any claim to fame, it's the FIRST AND ONLY fuel injected motocross bike made and totally legal to race in the AMA. A correction is in order.

   Dream on! Fuel injection came stock on the ATK 604 years before Cannondale even existed (which negates your FIRST AND ONLY claim). It should also be noted that ATK sold 1500 bikes a year for decadesunlike Cannondale that barely sold any bikes. We'll stick with the phrase, "but that is only because it doesn't (fuel injection) come stock on any bike" because we are talking about bikes that people can actually buy in showroom today (not brands that went out of business years ago).

    We appreciate your loyalty to your favorite brand. Scott and Joe Montgomery would be proud--if only they had anything to do with Cannondale anymore. Your "big check" comment is idiotic and insulting. We have chosen the Suzuki RM250 as the best 250 two-stroke for three years running and Suzuki was not an MXA advertiser for the majority of that time. We are often criticized for choosing Yamahas based on the assumption that Yamaha is our biggest advertiser. Not true! Honda is our biggest advertiser. Contrary to your logic, if we were as crass as you insinuate it would have behooved us to write nice things about Cannondale so that they would have sold a lot of bikes and become a big advertisers--but the truth is that the bike was flawed and our responsibility is to the consumer. The fact that you have dedicated your life to Cannondale is admirable, but it doesn't make a silk purse out of a sow's ear.

    No corrections are in order.


GASOLINE: HEADING FOR THE HILLS
Dear MXA,
    I plan on spending the summer riding in the Mammoth Mountain area, but I am confused about what fuel to run. My buddy says that because of the lack of oxygen at high altitude that I will need to run 100-octane race gas in my bike. Is this true?

   No. Cylinder pressures are lower at high altitude, so you don't need extra octane. Just buy pump gas at the local station and don't worry about high octane.

2004 RM125: OFF THE CHART SAG
Dear MXA,
    I recently purchased a 2004 RM125 and I was wondering what settings you guys found best for the bike. I weigh in at around 150l pounds. At the moment the front end seems to be all over the place. My current sag is set to 100mm. but the static sag is at 55mm!!

   Your static sag is off the chart. The 2004 Suzuki's suspension was way too soft. Slow, light and ex-mini riders can get away with the stock suspension, but heavier or faster riders must stiffen up the suspension right away. In our opinion, the best thing you can do to the 2004 RM125 is throw a stiffer set of springs at it front and rear. The forks need 0.43 kg/mm fork springs to help them stay up in the stroke. With the next stiffest fork springs we were able to run the compression and clickers at 10 out, which leaves lots of room for adjustment.

    As soft as the forks were the rear shock was even more buttery. Suzuki completely redesigned their linkage for 2004, but with the stock spring rate the rear end felt like a giant pogo stick. With the stock spring rate we had to run the compression at 3 and the rebound at 4 just to get the rear end to settle. We switched the stock 5.0 kg/mm spring for 5.2 and couldn't believe the difference. Let body weight be your guide. Under 140, try to run it stock. Over 140, go stiffer.

    We ran the rear suspension with 98mm of sag, the compression at 10 out and the rebound on 12.
    
    On another note, we dropped the mainjet to a 380 and ran a half clip leaner needle, but this will depend on your local conditions.

2005 YAMAHA YZ250: SUSPENSION
Dear MXA,
    I just bought a new 2005 YZ250 two-stroke. What are MXA's suspension settings & sag amounts?

   With every model year Yamaha has tried to lessened the YZ fork's tendency to bottomand 2005 was the first year that they succeeded. The 2005 AOSS (air oil suspension system) forks were way better than anything they previously offered. Although the 2006 SSS (speed sensitive suspension) forks are much better than AOSS.

    The 2005 AOSS forks resisted bottoming, absorbed little bumps with ease and didn't get harsh over the medium-sized stuff. But, they really tend to slow down quickly at the end of the strokewhich is jolting in high-speed bumps The average rider should start with the compression on 12 out and the rebound on 10 out (and turn in compression in to eliminate divinguse the dust line on the fork leg as your guide for compression).

    For 2005 Yamaha upped the shock spring rate from 4.75kg/mm to 4.9 (which is what we ran in •04). You would think that the spring rate change would make the new forks feel like our modified forks from the year before. Nope. For •05 we raised the shock spring from a 4.9 to a 5.0 or 5.1 (depending on rider weight). If you weigh over 175 pounds or go faster than the typical rider, go stiffer. We made the swap and loved the plush feel. Depending on your track, set the rebound on 12 clicks out and the low-speed compression on 12.


CRF450 STEARING: AGAIN

Dear MXA,
    I have been reading the info you have given on steering geometry for the CRF450's. I feel my 2006 understeers, so would putting a set of 20mm RG3 clamps be a waste of time with the geometry it already has?

   More than likely putting 20mm offset triple clamps on your 2006 CRF450 would aggravate the understeer. Less offset (going from 24mm stock to 20mm) increases trail (which is a measurement from where the virtual head tube hits the ground backward to the center of the front wheel's contact patch), increased trail improves stability, but is really not conducive to rapid cornering. The best way to move towards oversteer is to lessen trail or increase the head angle.

    The paradox in this scenario is that from 2002 to 2004, the understeering CRF450 was fixed by increased trail, but that had to do more with other inherent problems in the early CRF chassis. In 2005 (and thus 2006) Honda made a boatload of frame changes and they changed the fork offset (at the front axle instead of at the triple clamp) at the same time.

    You will have better luck in lessening understeer by sliding your forks up in the clamps, which will steepen the head anglea bigger contributor to turning prowess than any other number on a bike's chassis.


SAVE OUR TRACK
Dear MXA,
    There is a place in Georgia called Durhamtown, which for some reason is under attack by the state and the local new media.  There have been some injuries and a few deaths, which are unfortunate, but a grim reminder of the danger of this sport. Durhamtown is a safe place to ride. The owner has many rules that every rider must follow (i.e. helmets, one-way trail, speed limits in heavy travel areas). There are EMTs on site every weekend. Durhamtown personnel patrols on all the trails and trail sjust for beginners. What can we (hundreds of rider who enjoy this place every weekend) do to help this place we love.

   Over the years, we have seen this scenario take place at local tracks many timesand in most cases it is difficult to organize a loose and casual group of riders to do anything until it is too late. But, I do know thisthe bad publicity that hurts a track can be turned into good publicity through the same media. As much as Cycle News, MXA and Racer X may seem like media sources that can helpwe are preaching to the choir. You need to go to the same local media sources that are part of the problemnewspaper, TV and radioand help educate them to your side.

    How do you go about this? Good question. Here is what other tracks have done: Offer the track for local charity events; hold ride days; invite the morning news crew out to do a feature (teach the reporters how to ride and bikes like a CRF150 or TT-R125); Make phone callsnot to whine about bad coverage, but to suggest good coverage.

    Lots of facilities, from airports to race tracks to BMX parks to hunting clubs, are under attack. The ones that survive are the ones that can make a meaningful connection to the community. A track keeps kids off the street. It is a family sport. A track can be a great way to keep people from riding illegally (this was the pitch that drag racing tracks used in the •60s).The track should adopt a local charity and make connections with the public servants.

    This isn't easy to do, but you don't win a war by fighting hand-to-hand with a TV exec or a newspaper editor or the mayoryou win it by winning over convertsfrom cub reporters to the children of the mayor.

    We hope you can rally the troopsbecause that is really the hardest job.    

2006 YZ250: SET-UP
Dear MXA,
    Based on your test the 2006 YZ250 it sounds like it has a ton of potential to work great, but I seem to be struggling with mine a bit. This is my third YZ250, so I'm not exactly a rookie at this game. Any settings you found to work well would be greatly appreciated for me to use as a baseline.

   Since you have experience with the YZ250 you probably understand the importane of the new 2006 suspension components. Last year Yamaha used AOSS forks. AOSS stood for Air/Oil Separate System. The 2006 forks are called SSS for Speed-Sensitive System.

     There is two types of damping: position-sensitive and speed-sensitive. Last year's AOSS forks were 70 percent position-sensitive. The damping rates were dictated by the position of the fork's piston inside the cartridge rod. In simple terms, The farther the piston moved down in the cartridge rod, the stiffer the damping. On your 2006 SSS forks, damping is 90 percent speed-sensitive. By switching from 30 percent speed-sensitive damping to 90 percent for 2006, the forks will stay higher in their stroke, have a more linear damping rate and resist bottoming. Speed-sensitive damping gets its name because the damping rate is determined by the speed at which the piston moves though the cartridge rod.  Yamaha's speed-sensitive damping has a more linear damping curve. A linear curve gets steadily firmer as it goes. There are no hills or valleys in the damping curve. It gets stiffer at the exact same rate in the first half of the travel as in the second half.

    In our opinion, the SSS forks are better on every size bump than the previous YZ250 units, which fought back at the end of the stroke. SSS damping is regulated in such a way that the spring rate had been reduced from 0.44 kg/mm to 0.43 kg. They resist bottoming, absorb little bumps and don't get harsh over the medium-sized stuff. The average rider should start with the compression on 12 out and the the rebound on 10 out.

    As for the rear shock, it is very modern: The 2006 shock has an 18mm shock shaft. That is 2mm larger than last year's shock shaft. The larger shock shaft displaces more oil, which means that more oil is pushed through the valving sooner, which results in a more sensitive feel on small chop. All the internals parts of the YZ250's Kayaba shock are Kashima-coated to reduce friction. In addition, the shock reservoir has been increased in volume by 30 percent larger reservoir to help control the heat. The shock spring is made from titanium. It is rated as a 4.9 kg/mm spring. Last year we suggested a stiffer spring for riders over 180 pounds, but in testing stiffer springs this year we didn't like the feel.

    Once you have it dialed in it is a very good shock. We ran the race sag at 100mm, high-speed compression on one turn out, low-speed compression on 11 clicks out and rebound on 9 clicks out.

    Remember, those are just starting points that you can work off of for your local track conditions, weight and speed.



KTM 250SX: ALL YOU NEED TO KNOW
Dear MXA,
    I just got an 2006 250SX and am looking for a base setting for suspension and jetting. I'm 6' 3" and 195 pounds before gear (with long legs). Will the stock springs work? I ride outdoor MX and an occasional cross0country. Also I believe you recommend a certain PC pipe?

   Here are a few tips for your KTM 250SX:

    (1) Springs: You will not need stiffer springs. It should handle a 195 pound rider of your height no problem.. In fact, the KTM is one of the better bikes for tall riders in terms of ergos.

    (2) Pipe: Pro Circuit built a special pipe for Jeremy McGrath, when he was riding a KTM, and while Jeremy never really got full use out of it, Pro Circuit does sell Jeremy's pipe. It is very very good.

    (3) Jetting: In the warmth of summer the stock jetting will be okay, but you might want to lean out the 42 pilot to a 40 and go for the optional NIEG needle over the stock NIEF (the NIEG is a half-clip leaner and comes with the bike).

    (4) Forks: We ran the fork caps 5mm up in the triple clamps (remember, the 2006 forks raise the front of the frame higher and thus can be slid up into the clamps much more than previous KTM forks). Our best settings were with the compression on 16 clicks out and the rebound at 18 clicks.

    (5) Shock: Set the high-speed compression at 2-1/2 turns out, the low-speed compression at 14 clicks and the rebound on 25. We tested sag settings as low as 110mm and as high as 100mm. We opted for 105 to keep the chassis more balanced. Too much race sag causes the front end to push at turn-in.

    (6) Clutch: The new Brembo hydraulic clutch feels more like a normal clutch than the previous Magura. Best of all, the Brembo clutch uses DOT 5.1 brake fluid instead of the Magura's mineral oil.



JODY'S BOX: MIA
Dear MXA,
    What has happened to the online archives of Jody's Box? I've been a huge fan of his stories since getting my first copy of MXA in 1980 at age 10. I always buy MXA when I can in the UK, but used to enjoy just going online during my lunch break.

   We sent this question directly to Jody, who answered thusly: "The boys at MXA's website forwarded your email to me personally because I am the one who told the website to take down all of the old Jody's Box columns. They wanted to keep them up, but I like to have the stories unveiled one at a time in the magazine--and not leave any trace behind me.

    "I have received lots of emails from people who want me to put them back up, but it isn't going to happen. I prefer that the stories disappear--that way, the ones I don't like I don't have to think about and the ones that I do like are more exclusive. I understand that this is a hardship in places where it is hard to get MXA on a regular basis.

    "There is a simple solution. MXA has a digital version--it is emailed to subscribers at the exact same time that American readers get their paper subscriptions. It can be downloaded to your hard-drive. It has zoom, search, active websites and, best of all, gets to Europe months before the paper versions. And it is cheap. Go back to the home page top rad all about it."

HOUR OF POWER
Dear MXA,
    I bought an hour meter for my CRF250 and mounted it on the left frame spar, but it isn't working. What is the best spot to mount it and is there any thing I am doing wrong?

   We mount our hour meters on the right side of the frame (behind the head tube, in front of the gas tank). We remove the gas tank and run the wire down the backbone to the spark plug wire. It is important that you wrap the hour meter's lead wire around the spark plug wire tightly and several times. It gets its juice of the electricity flowing into the enginethat way it only runs when the engine runs.

    We have used both two-sided tape, pop rivets and stick-on Velcro to hold it to the frame.

    If you have any problems call DR.D at (951) 808-1114 for help.


KX450F: MISSING LINK
Dear MXA,
    I am interested in the linkage system for the KX450F, but I got on the Pro Circuit website and could not find that linkage for KX450F. I was hoping you could tell me where you picked up that linkage

       Pro Circuit definitely makes a link for your KX450F. It may not be on their website yet, but if you call (951) 738-8050 they can tell you all about it.


2005 YZ250F: SUSPENSION SETTINGS
Dear MXA,
    I have a 2005 YZ250F. I was wondering what the best suspension settings the MXA test crew found for a 190 pound Intermediate rider.

   In 2005 the YZ250F used Kayaba AOSS forks. It stands for Air/Oil Separate System. These were Kayaba versions of Showa's Twin-Chamber forks. We call them Showabas. They're not exact copies of Showa's Twin-Chamber forks, but they're close.
    Forks: Set the compression on ten and the rebound on 12. Enjoy.
    Shock: We ran our sag at 97mm. In a world that has come to think of 105mm as an acceptable number the YZ250F works much better with a little less sag. We ran the compression on 8 out and the rebound on 10.
    These are starting points, you will have to modify them for track conditions.

AMA POINTS AND OTHER THINGS
Dear MXA,
    I find it confusing that Chad Reed is only two points behind Ricky Carmichael with only two wins. I think it would be interesting and informative to break down the points chase and show where points were won or lost, including the points from that illegal gas debacle.

       As with any points system, consistency is rewarded more than wins. The difference between winning and finishing second in a race is only three points (25 for first and 22 for second)--and only five points between first and third (25 to 20)--which means that if a rider fails to score any points, like Ricky did when his shock spring broke, he loses 25 points (more accurately 24 because he would get one point for finishing last in the main event). Simple math would tell you that it would take eight wins to get back those 24 points (if Reed finished second every time). The math is 8 X 3 = 24.  If Reed was third and Ricky was first it would take less that five wins in a row (because Ricky would gain five points on Reed). The problem for Ricky is that James has been winning as a of latemeaning that Ricky has been getting 22 points and Chad 20which is only a two point gain. So when Chad won and RC got sixth last weekend, that was a 10 point swing for Reed (which erased all of the Ricky's second place finishes versus Chad's thirds). And that is how Reed got so closehe hasn't had a terrible race, while Ricky and James have.

AMA points are paid as follows:
    1. 25
    2. 22
    3. 20
    4. 18
    5. 16
    6. 15
    7. 14
    8. 13
    9. 12
    and so on until 20th get one point.

    No points were lost in the fuel incident because the AMA rescinded RC's points penalty a few days later.



CHAD REED DEFENDER
Dear MXA,
    I just ingested the May issue, and one thing really jumped out at me. In your top 100 heroes of Supercross, you mentioned a number of riders, including Stewart and RC, but not Chad Reed. You mentioned Reed's mechanic and about 90 industry insiders, that included some of the Team Yamaha staff, but not Reed. I know he's not as flashy and fast as RC and JS, but he has led laps, led the points, won two races, and gutted out that incredible second place ride at Daytona two days after a separated shoulder. I think Reed at least deserves to be mentioned.

   We certainly weren't slighting Chad in the May 2006 issue--anymore than Travis Preston, Grant Langston, Ivan Tedesco or a host of other riders that we chose not to include. We did include Team Yamaha's Alan Olson, Keith McCarty and Jim Perry because the story was about people behind the scenes. We added in riders like Carmichael, Stewart, Lewis, Wey, Villopoto, LaRocco, Millsaps, Short, Jimmy Wilson to add a little balance. Additionally, we had a stand-alone Chad Reed interview in the April 2006 issue.

CRF450: HEAD SHAKE AND  HANDLING
Dear MXA,
    I have a completely stock 2006 CRF450. Is there anything I can do to calm the steering down when charging sandy straight-a-aways?? As I pick up speed the steering seems to get nervous. I have no other handling problems with the bike (it's actually my favorite bike I've ever owned).

   You have several options for calming down head shake:

    (1) The quickest and easiest to do is to slide your forks down into the triple clamps. The farther you slide them down, the slacker the head angle. As the head angle slackens, the trail increases. The more trail a bike has the less likely it is to shake. The forks can easily go down until the top of the clamp is even with the threaded-on portion of the fork cap (on many bikes we have actually submerged the forks capbut you shouldn't have to go that far).

    (2) While you are sliding your forks down, check your race sag. With you in the saddle, the bike should sag approximately 100mm (when measured from the rear axle to the rear fenderin a line similar to the swingarm stroke). If the race sag is less than 100mmsay 95mm, this keeps the rear end high and steepens the head angle. Check the sag and set it on 100mm.

    (3) A Honda shock has high-speed compression damping (the large dial on the top of the shocknot the one with the screw driver slot). Turn it all the way in and count the number of turns (it should be less than two). Then turn it back out 1/8th of a turn more than it was initially. This will allow the rear end to ride lower under acceleration (conversely, turning the high-speed compression adjuster in will make it ride higher). This is not related to race sag.

    (4) Your last choice should be a steering stabilizer (like WER or Scotts). They are designed to stop head shakebut are expensive.

OXYGENATED GASOLINE
Dear MXA,
    I read that you could get three more horsepower out of a CRF450 by using VP racing fuel. I was wondering how much more horsepower you could get out of a 2006 KX250F by using the same gas.

    Oxygenated fuel would add approximately 1-1/2 horsepower to a 250F. I'm sure that you also read that it cost $13 a gallon...and it can't be left in your carb for more than three weeks without causing a residue problem. That is no problem if you ride the bike every week...but sitting unused with VP U4 in the float bowl is not good.

JIM O'NEAL'S SHOTGUN
Dear MXA,
    I was trying to figure out what is written on the butt stock of Jim O'Neal's shotgun on page 57 in the May 2006 issue. Did he write that himself or is it doctored? The writing in question is just below the "Bush 04." It says something "rat." What does it say?

   It is the date of when Jim's shotgun was cleaned last. He writes the date on the stock to keep track of its regular maintenance.

KX250F: COOLING SYSTEM
Dear MXA,
    I recently purchased a 2004 KXF250. I have installed a Boyesen water pump/oil cover with impeller to aid in cooling. I am thinking of running either Engine Ice or WaterWetter. Which would you recommend ?
 
   We used WaterWetter or Maxima Coolanol on our KX250F (both were recommended by the Pro Circuit team ). Also we changed the 2004 radiator cap (to a 1.6), drilled out the louvered radiator guards and ran the Boyesen impeller.

CRF250: PUMPS, PIPES AND SPRINGS
Dear MXA,
    I read the May issue of MXA (which gave all the smart mods for the CRF250R) and I ordered the TBT insert (couldn't afford the whole carb) and am looking to get some new clutch springs. What brand of clutch springs should I get? Also...would the Boyesen Accelerator pump cover be of any use with the TBT mod? I am also going to be able to get the Yoshimura exhaust at 50% off due to sponsorship (when I get the money). Will this give me the same power increase as the Dr. D singe exhaust system? You have to admit it looks pretty cool. OK...so I asked several questions. Please help me out and I promise to leave you alone until I find myself completely stumped.

   Here some quick answers:
    Clutch springs: We got stiffer clutch springs from Pro Circuit.
    Boyesen QuickShot: We tested every combination of 2005 part for the 2006 CRF250 and we tested the Boyesen QuickShot, the 2005 carb and the TBT carb mods. We felt that the 2005 carb eliminated about 95 percent of the bogging, the TBT mod about 85 percent and the Boyesen Quickshot about 50 percent. We did not put the QuickShot on the 2005 carb or on the TBT carbso we can't tell you if the combination is any better. But, when your bike is jetted perfectly, we don't see any real advantage to the QuickShothowever, on bikes with burbles, hiccup and bogs, the QuickShot is a big help.
    Yoshimura pipe: We loved the Yosh RS3 twin-pipe on our 2006, but when we tested the 2006 DR.D single pipe we felt that it worked better than the Yosh. We agree with you that it didn't look anywhere near as cool. In our case, we took everything off of a 2005 (airbox, carb, subframe), so we couldn't mount a twin even if we wanted to.

CRF250: SPARK PLUG CONFUSION
Dear MXA,
    I just bought a 2006 CR250R. The sparkplug that I am supposed to use is an NGK BR9EG-N-8.  I went to my local dealer and he didn't have one so I bought a BR9EG instead. Can I use this plug without any problems?  What is the difference between these plugs, if any?

   The quick answer is that you can run a BR9EG instead of the BR9EG-N-8.
    In BR9EG-N-8 the alphanumerics can be translated thus:
    The B means that it is 14mm thread size.
    The R means it is a resistor type.
    The 9 is the heat range (9 is colder than 8).
    The E is the thread reach. E represents 19mm.
    The G means it is a fine wire nickel alloy electrode.
    The N means it has a side electrode.
    The 8 (at the end) means it is a wide gap plug (0.8mm).

    The BR9EG that you want to use is fine...depending on weather and gas you could also use a BR8EG (a little hotter plug)


CRF450: PUSH COMES TO SHOVE
Dear MXA,
    I recently bought a 2006 CRF450. It is my second, I had an 2003 prior to this one. My 2003 handled great with the stock offset, but on my 2006 the front wheel washes out really easy when exiting a turn. Any ideas to make this better?
 
 Get rid of the stock Dunlop 742 front tire. It doesn't work in the real world.


YZ450F: QUICK SUSPENSION NUMBERS
Dear MXA,
     I have just purchased a leftover 2004 YZ450F. Could you dig up some of your suspension settings for the big Yamaha for me?
 
    The biggest rap against all YZ forks has been bottoming. With each model year Yamaha has lessened the the YZ fork's tendency to clank, but it seems that they were held back by the rubber baby buggy bumper bottoming system of the older model 46mm forks. For 2004 Yamaha went to 48mm forks (with long, conical, male/female, hydraulic bottoming cones). It's old technology, but it worked better than the bumpers of 2003. We turned the compression out to 12 and the rebound to 10.

     As for the shock, we liked it, but the difference between one or two clicks was immediately noticeable. That was a good thing--unless we were one or two clicks off. We spent a lot more time making clicker adjustments on the 2004 YZ450F than any other bike that year. When we got it right it was very very good. One click off and it kicked. Depending on your track, set the ride height at 100mm, the rebound on 12 clicks out and the low-speed compression on 12.

    Also, we replaced the stock 48-tooth rear sprocket with a taller 47. Why? Although most pros can handle the 48, slower riders and recent two-stroke transplants found that the 47-tooth sprocket allowed them to use second gear for starts, most corners and downshifts. In many cases it eliminated having to shift into third on the exit of turns, which decreased stalling. If you are having trouble finding the right gear, stalling in tight turns or getting a good start--consider a 47.


YZ250F: NUMB HANDS
Dear MXA,
    I own a 2002 YZ250F (I'm hoping to get a new one in 2007) and my fingers go numb after about fifteen minutes on the bike--mostly my throttle hand. I have aftermarket upper clamps with rubber bar mounts and an aluminum throttle tube on TwinWall bars. Am I holding on too tight? Are my bars worn out? My local shop said to fill the bars with liquid filler foam and that all the Pros do it. What should I do?

    Unfortunately, we don't think that the problem has anything to do with your bike. You have covered most of the bases (and in scientific testsfilling the bars with construction foam doesn't do anything for vibration and no factory riders do this)although there are heavy lead weights that do a decent job of toning down vibes inside handlebars. The TwinWall bars are probably overkill and you would be a little better with Renthal Fatbars. Again, we don't think that is the root of your problem because you have the same basic bike as thousands of other riders, who don't have your problem (did you check your motor mount bolts?)

    We'd be willing to bet that your ulnar nerve, which runs across the palm of your hand, is playing a major role in your problem. We say this because it has happened to factory riders in the past. Additionally, most riders get arm pump, numbness and hand troubles on the clutch sidenot the throttle side.

    Here are three things you can try.

     (1) Relax your grip. You don't have to hang onto a motorcycle with all your might. Grip the tank with your knees and allow your hands to float on the grips.

     (2) Hold the throttle like you would a door knob. Don't grip it with four flat fingers wrapped around it in an even row. Bring your elbow up and slide your hand down the end of the throttle with your thumb running underneath (as close to parallel to the grip as possible)that will take the pressure off your palm. Open and close the throttle with a twist of the wrist, like turning a door knob.

     (3) Change gloves. If you use padded palms, switch to unpadded gloves. If you have unpadded gloves switch to padded gloves.


RM250: THE WHOLE BALL OF WAX
Dear MXA,
    I just bought a 2002 RM250, from your experience can you tell me the best gearing? I'm running 13/50 right now, the best carb settings, and the best suspension settings for a 165 lbs. rider. Thanks.

   Good luck with your new bike, you will need it for the jetting. We have traditionally had jetting problems with Suzukis, and the 2002 was no different. As much as Suzuki hates to admit it, their bikes need race gas to perform at their best. Without race gas, you will chase a rich, lean, rich scenario with every twist of the throttle. The combination of a Throttle Position Sensor and Power Jet, which were the rage a couple years ago, only confuses efforts to get the RM250 properly jetted.
  
    Here is what we ran in our bike for SoCal's sea-level tracks:
  Mainjet: 170
  Pilot jet: 45 (48 stock)
  Power Jet: 50 (45 stock)
  Needle: N8RH
  Air screw: 1 1/2 turns
  Clip: 4th (3rd stock)

     As for the gearing, bikes with light flywheels present some serious gearing problems. The lack of flywheel inertia translates into beaucoup trouble in sand, deep loam and heavy going. Unfortunately, gearing it down aggravates the problem because of the shortness of the torque curve. We tried gearing the 2002 RM down, but shorter gearing only translated into an even shorter powerband.

     The Suzuki is at its best on tight tracks and hard dirt. It's best to run this engine tall and use the clutch to compensate when it bogs down.

    When it comes to the rear suspension the 2002 RM250 was completely out of balance. The rear of the RM250 felt like it has two feet of suspension travel, while the front fork felt like it is stinkbugged downward. Making matters worse is the minimal compression damping on the rear shock. It gives the rider the false sensation that it is stout enough, but as soon as he powers through a G-out or lands from a big jump, it bottoms out. The quandary is that turning the compression clicker in doesn't stop the bottoming, but it does increase the harshness over smaller bumps.

    To get the most out of the 2002 RM250, you will need a stiffer shock spring. What was our best setting?
  Spring rate: 5.0 kg/mm (4.8 stock)
  Race sag: 98 mm
  Lo-compression: 8 clicks
  Hi-compression: 1 1/2 turns out (1 stock)
  Rebound: 11 clicks (13 stock)

     In 2002 Suzuki traded their normal Showa's Kayabas. The major test rider fork complaint was identical to the shock complaint. On the setting where the forks felt best in the small to medium bumps, they bottomed. When the compression clicker was turned in to stop the bottoming, the fluid feel disappeared.

    We ran compromised settings for each and every track. But, more often than not we found ourselves with the compression clicker turned all the way in. Not good--and a definite sign that stiffer fork springs are called for.
   
    What was our best setting? For hard-core racing we recommend this set-up:
  Spring rate: 0.44kg/mm (0.43 stock)
  Oil height: 454cc
  Compression: 8 clicks out
  Rebound: 14 clicks out
  Fork leg height: level

CRF450: SUSPENSION SETTINGS
Dear MXA,
    I just bought an '06 CRF450 and I was wondering what settings you used on the suspension when you did your test of the bike?

   The 2006 suspension is firmer on compression than the '05 model, which makes it better overall. It stays a little higher in the stroke and fits a wider variety of riders. That said, MXA test riders have a tried-and-true fix for Showa forks that has worked since 2002. We install stiffer 0.49 kg/mm forks springs and lower the oil height from 385cc to 375cc. We set the compression and rebound on 10 clicks out. With the stiffer fork springs and lower oil height, the fork is plusher over small bumps, stays higher in its stroke on consecutive hits and can handle the big landings. Do it.

    The shock is decent. We set the sag at 100mm, low-speed compression on 12, high-speed at 2 turns out and rebound on 10. It was a little kicky over braking bumps (which required a delicate touch with the rebound adjuster).


YZ450F: TARGET PRACTICE
Dear MXA,
    What is the target rider weight and ability level for the 2006 YZ450F's stock suspension?

   We called Yamaha's official test rider, Doug Dubach, to get the official answer. Doug said, "The 2006 YZ450F is design for a 180 pound rider that is somewhere between Novice and Intermediate skill levels. But, it isn't that cut-and-dried. Spring-wise the YZ450F suspension will work with riders from 150 pounds to 200 pounds without stretching the preload capability."

TWO-STROKE VERSUS FOUR-STROKE
Dear MXA,
    I want to make the change from two-stroke to four- stroke. I am hesitant due to the fact that I really know nothing about four-strokes or the maintenance they required (compared to the two-stroke. I don't know if I want a 250F or a 450. I currently ride a 2003 RM250 and I weigh 190lbs in street clothes. Which bike would you recommend for me?

   We can't tell you what to buy, but since you ask, here is what we think you should buy. If you are intent on getting a four-stroke, and that is the trend, you should get a 450. Since you are coming from a 45-horse RM250, we can't see how you'd be happy to go to a 35- horsepower 250Fand at your weight you have the muscle mass to handle the 50 horses of a 450 (plus the extra 15 pounds).  

     There is a cost factor involved. Two-strokes, which are still viable in the 450 class because they make decent horsepower with light weight and snappy response, are much cheaper to maintain. They have very few moving parts, so for the price of piston, rings and gasketsyour two-stroke can be brand new. A four-stroke has about 10 times as many moving parts. In a rebuild you can expect to pay five times more for the parts you need to make a four-stroke new. And, if the four-stroke blows up before you rebuild itthe cost ranges from $1700 to $3000 (depending on how much damage occurs). That sounds scary, but most four-strokes don't blow up if they get regular oil, air filter and bolt maintenance (at least not for two to three years).

     We would recommend that you get a Honda CRF450 or a Yamaha YZ450F. Not that you couldn't live happily-ever-after with a KTM, Suzuki RM-Z or Kawasaki KX450but, since you are new to four-strokes the YZ and CRF offer more chances to seek help from others ridersjetting, suspension settings and the ability to borrow a part at the trackjust based on the popularity of these two machines.

LOOKING FOR THE RIGHT BAR
Dear MXA,
    Could you tell me what kind of ProTaper bar comes stock on the 2006 Yamaha YZ250F? Supposedly the bike could handle better with 10mm taller handlebars, but I need to know what kind of bend the stock bar is first to be able to tell which taller ProTaper bar to purchase.

   Unfortunately, MXA never asked ProTaper the exact name of the stock bend because we changed them on the first ride (initially using spacers under the bar mounts,) but ProTaper did sent us a set of ProTaper "YZ High" bars which were taller than the stockers and had the same bend. Your dealer should be able to get this bar for you.

LONG ANSWER TO A SHORT QUESTION
Dear MXA,
 I've read every word that MXA has ever said about the 2006 YZ450F and Honda CRF450. I would normally just buy the Honda, but this year the blue bike got so many revisions that it seems like the one. Can you please clear up any real world differences between the bikes.

   The differences between the YZ450F and Honda CRF450 are very great. The bikes have very different traitsnot necessarily bad traits, but each does things in its own way. Here is a quick list:

    (1) Power: Both make 50 horsepower. Honda's style of power is quite old school. It chugs a little more and goes pockity-pock at low rpm. It is more of a thumper and because of this it feels very manageable and, we think, hooks up a little better than many other four-strokes. The Yamaha is a much more modern engine. It has a five-valve Genesis head, 100 percent tungsten counter-balancer and a power delivery that is much smoother. It rolls on nicely and revs cleanly. The simplest comparison is that the CRF450 feels like big XR400 while the YZ450 feels like a 450cc automobile engine.

    (2) Handling; The previous Honda's (2002, 2003 and 2004) were bad handling bikesregardless of what people like to think. Over those years, Honda, who was well aware of the front-end shortcoming of the CRF450, produced three completely different frames. In 2005, the frame came around to its' current excellent level. The Honda is a very good bike at turn-in (although a little clanky on the entrance) and superb from center-out. The Yamaha's greatest handling trait is its light weight (not that it weighs any less than the CRF). Thanks to centralization of mass (lowering the radiators, lowering the seat height, lowering the crank height and rotating the rotating mass of the piston back towards the center of gravity), the YZ450 feels 20 pounds lighter than the CRF when leaned into a corner. That said, the YZ450F has some push at center-out (which can be mitigated by better front tire choice and slight chassis adjustments at the forks).

    (3) Suspension: No suspension system works until it is set up properly for the rider and track conditionsbut all things being equal the YZ450F's Kayaba SSS forks are better than Showa's Twin-Chamber forks. Again, the CRF450 forks are very good (especially when compared to KTM, Kawasaki and Suzuki--just not to the Yamaha).

ECU'S AND EFI: KISMET
Dear MXA,
    With rumors of EFI 450s for 2007, will this be much better than their carburated predecessors?

   Every manufacturer is working of EFImaybe for 2007 and maybe for 2008. Most companies already have an EFI ATV on the market. As for the difference between EFI and carburetion, I expect that as far as ease of jetting goes, power delivery and throttle pick-up with EFI will be betterbut for the average racer, and I mean racer not rider, carburetion is foolproof (once it is right). Most racers ride hard...and ask their carbs to produce fuel on demand, which a carb is very good at because it works on engine vacuum. Racers don't cruise very often, go from sea level to 7000 feet on the same day or want to pay the premium price for untested stuff. Additionally, unless the motocross bikes gets more sensor probes and electronics than the ATV's, there will be a brisk market in hopped-up ECU's to make the EFI work when you change pipes, port the head or open up the airbox.

YZ450F STICKER
Dear MXA,
    Please help me! I have my first race in one week. I bought a 2006 YZ450F and love every aspect of it except the front tires won't stick in a corner, either flat of sandy. I ride a lot of sand and intermediate terrain. I heard word of 27mm offset clamps... Does that help? What tire?

   It is difficult for us to analyze your problem without actually seeing your personal "big picture." Since you say that you ride on sand and intermediate dirt, we have to wonder what front tire you have on your YZ450F? The stock tires on the YZ450F are a Dunlop 739 front and 756 rear. The 739 is designed for hard terrain. It has short knobs with considerable buttressing and a closed pattern. It is not a good intermediate-to-soft tire because it doesn't have enough tread depth for loose or loamy dirt. As a rule, we run Dunlop 756 front tires on our YZ450F in Intermediate terrain and a Dunlop 773's in full sand. On hard terrain we run about 15 pounds in the front tire, 14 on intermediate terrain and 13 in the sand. Front tires are critical to performance (and front tires vary the most in performance).

    Based on track conditions we raise and lower the front fork height (higher up in the clamps will steepen the head angle and make the bike turn sharper, while lower will calm it down at speed and slow down the cornering). This is the most valuable tuning tool that a rider has because it is one of only two ways to change frame geometry on the spot (the other is to change race sagwhich also changes the head angleamong other things).

    As far as front offset goeswe do run 27mm front triple clamps on our YZ250F, but do not recommend that offset for the 450. At the moment we are testing 23mm offset for the 450, but have not finished the test cycle and aren't totally convinced (by the way, stock offset is 25mm).

LIFE SUPPORT FOR THE CRF250
Dear MXA,
    In your April 06 issue you rated all the bikes. I have a 2006 CRF250 and was wondering why you came to the conclusion that it blows up with regularity? Is there anything I can do to stop it from happening?

   We came to that conclusion based on the fact that we personally know a lot of people who blew them up (and from dealer reports). But it doesn't have to happensince most of the failures were caused by poor maintenance. The most important thing is to watch the engine oil like a hawk. If you let the oil go down by 100cc, it will lose the next 100cc in half the time, and the next 100 cc in half of that time and so on. Low oil height increases engine temp and cause premature wear, galling and destruction of the engine. The CRF250, because of its split engine and tranny oil system, has about half of the engine oil as a YZ250Fand the oil needs to be checked after every ride.

IN OR OUT WITH SHOWA
Dear MXA,
    When turning the clickers on my Showa suspension, which way is in, and which way is out?

   "In" is clockwise, "out" is counter-clockwise

SNAIL CAM ADJUSTERS
Dear MXA,
    Why don't the old-style cam adjusters work on today's machines? I still see them on late model trail bikes. Today, I have to put my glasses on, stand on my head to see the hash marks and have a hand full of wrenches for each bike.
 
   The main reason that snail cam-style chain adjusters have fallen out of favor is chain torque. The trail bikes that use the old-style adjusters are low horsepower engines that don't land hard from big jumps (with the throttle on).

BEST BIKE FROM A DECADE AGO
Dear MXA,
    My local AHRMA club has developed a "Decade" class, where any machine 10 years old or older is authorized. I am considering a 1996, 1997 or 1998 KX250. Any suggestions?

   The 1996 and 1997 Kawasaki's were very good machines. The '97 and '98 models were exceptionally good. The powerband of choice at the time was low-to-mid and the KX250 was the class leader in this style of power.

    The '96 had very soft forks and overly stiff rear suspension (for the time). It defined stinkbug at the time.

    The '97's rear suspension was light years better, but the forks were still stinkbug. The engine was awesome, but it had a weak clutch (we ran XR400 clutch springs from Barnett in it). The '97 model had a longer swingarm than the '96 model and this was a big plus to the handling--it put more weight on the front wheel and moved the rider forward. These Kawasaki's were "upright handling" bikes. They liked to be steered through the corners more than leaned over--that was Emig's style. If you had to buy a bike, any brand from 1997, the KX250 would be the best choice since it was the best 250 in 1997.

CRF450 UNDERSTEER
Dear MXA,
    I own a 2003 CRF450. Currently, I run a Dunlop 756 19" x 120 series rear (110 is stock) and a Dunlop 742front. Further, I have a 22mm offset triple clamp with the forks set in the stock position and rear race sag at 95mm. The bike still understeers. It is bad at turn-in and mid-corner, but fine in high throttle exits. My question is: Would running a 100 series 756 tire offset the understeer, or would the narrower profile cause me other fits?

   The 2003 Honda CRF450 had a tendency to wallow in the center of the corner, which required throttle steer to bring the back end around. The normal fix for this, back in 2003, was 20mm offset triple clamps, careful adjustment of fork height and the best possible front tire.  Base on your letter, you are on the right track...except for a couple minor things.

    (1) The 742 front tire does not help with your understeer. It is a rather vague front tire that was designed for Supercross a few years agoand only works on moist crumbly dirt. It is a tire that we take off if we have any cornering problems.

    (2) Your triple clamp choice (22mm) should be fine, but you will need to raise and lower your forks to steepen the head angle to suit the conditions. Too high and it will oversteer. Too low and it will understeer.

    (3) The 120 rear was a bad idea and the 100 rear would be an equally bad idea. The 120 profile is very flat on the bottom and tends to resist rolling onto the side knobs (when compared to a 110). This makes the bike stay upright too long into the center of the corner. It also hooks up at low speeds which makes the front tire pushwhich of course aggravates understeer). A 100 rear tire would spell an end to getting a good start on cement because it would be more prone to wheelspin. It just isn't enough rear tire for a 450.

    We would recommend that you go back to a 756 front and 756 rear (110), balance your suspension out as much as possible and then focus your cornering tests to fork height changes.

GREAT AND UNITED
Dear MXA,
    I was wondering if you could give me advice or information on motocross schools within the United Kingdom, as I am intrested in motocross but I live in England?

   Sorry, but we are Americans and the only thing we know about England is that you turn right at Iceland to get there. Try this website: www.motoxmag.co.uk

RAW METAL AND RUST
Dear MXA,
    What kind of maintenance is required for a pipe such as the Pro Circuit Works pipe? I have read in different places that they corrode if you don't maintain them.

   Because the pipes are raw metal--they rust. To stop this, we spray the pipe with lubricating oil (WD-40, Maxima, etc) and then we rub the pipe with a ScotchBrite pad. You have to do this about once a month (or immediately after any mud or rain race). You don't have to do this with plated pipes, but they don't look as cool.

LEFT-OVER 2004 RM-Z250
Dear MXA,
    I was able to buy a leftover 2004 RM-Z250 for the right price and I have never owned a four stroke. Would you be kind enough to dust off your 2004 setup specs?

   How much do you want to know? Here is a quick list of 2004 set-up, traits and problems

    (1) Heat: The 2004 radiators are smaller than the 2005 radiators. The 2005 model has radiators that are are 40mm longer and have a 17.8 percent larger core area . We swapped the stock 1.1 radiator cap on the 2004 for a 1.6.
    (2) Vibration: The RM-Z/KX-F engine doesn't use a counter-balancer. It vibrates.
    (3) Handlebars: The stock bars were steel.
    (4) Clutch perch: There is no on-the-fly clutch adjuster?
    (5) Tires: The stock tires were Bridgestone's 601 and 602 tires. Luckily, they should be long gone from your bike.
    (6) Suspension: It is unbalanced.
    Forks: The old school Kayaba units handle big hits and little bumps without any major complaint, but we had to do something to them to alleviate the stinkbug stance. The rear is high and front is low. Our remedial fix was to run the forks 5mm above the top triple clamp and run 105mm (and sometimes as much as 110mm) of race sag in the rear shock. We ran the forks as stiff as we could stand them on compression (approximately six clicks out) and the shock as soft as we could go (approximately 15 out).
    Shock: In our opinion the stock shock set-up is way off the mark. It is so over-damped that the rear end transfer loads to the front of the chassis--which in turns overloads the forks--often resulting in major head shake. Serious racers should invest in Pro Circuit's works linkage. It helps balance the bike out and soften the rear suspension. Unfortunately the RM-Z250 shock does not have high-speed compression adjustment--because our first move would have been to turn the dial out.
    (7) Gearbox: Third and fourth gear were weak in 2004 (proven by the fact that they were shot-peened in 2005 to make them stronger). The gearing benefited by adding one tooth to the rear sprocket.
    (8) Valve float: The RM-Z/KX-F engines valve problems were caused by valve float. Stiffer valve springs can fix this problem,.
    (9) Cam buckets: We ate through a set of buckets (where the cam rubs against them).

THE FABLED BLIND SIDE BEARING PULLER
Dear MXA,
    I am pretty sure that I read in MXA about where to find a blind side bearing puller and I can not seem to find that particular issue. If you could help me I would be very grateful.

   Try GG Mechanica at (888) 700-2382. They offer an excellent Beta bearing puller.

HONDA OFFSET QUESTION
Dear MXA,
    RG3 has different offsets on their clamps and I would like to know the best set up for my 2005 CRF450. I have Race Tech suspension and am very happy with the overall handling, but i feel like I need to get over the bars farther to get in the right position on the bike. What should I do?

   If you owned a 2002 or 2003 CRF450 we would recommend 20mm offset. On the 2004 we ran 22mm offset, but Honda changed the offset (at the axle dropout) and the frame geometry in 2005--to mimic the specs that everyone was using. The only difference between a 2005 and 2006 frame is that the •06 engine is dropped 5mm in the front, but this only provides a minor improvement in overall handling at turn-in.

    You sound like you know that your problem is one of set-up and ergos more than frame geometry. Before you buy handlebars mounts that will allow you to move your bars forward (which is cheaper than an all-new top clamp), just rotate them up-and-forward and ride (remembering that they will be taller and swept a little weird). That should give you a quick feel for having the bars farther forward. Many times for many riders, farther forward isn't better, but slightly taller is.

DEAD IN THE WATER
Dear MXA,
    Last weekend my brand-new KX250F refused to start after practice. It had worked fine before that, but nothing I did would make it start (including pushing it)? Where should I starting looking?

   That's simple. We suffered the same fate with our KX250F. For 2006 Kawasaki changed the cam chain stopper plate. The new stamped steel plate has little winglets that the •04-'05 stopper didn't have. On our bike, the winglet broke off and fell down into the ignition, where the small metal piece shorted out the ignition. That is where we'd look first. We replaced the 2006 stopper plate with the 2005 version (the part number is 13271-0169).

SINK OR SWIM
Dear MXA,
    MXA is always talking about stiffer valve springs, new valve seats and valve float, but I don't understand what the big deal is. So what? If the bike won't rev, shouldn't the rider just shift sooner?

   True, but if you have to baby your bike on top, you won't be getting all of its performance. The big danger of valve float isn't that the bike won't rev, it's that the valve and piston clearance will be reduced by the lag time. If the valves float they can strike the piston. This is catastrophic.

KAWASAKI KX450F HELP    
Dear MXA,
    I bought my 2006 Kawasaki KX450F before I got the issue of MXA with the test in it. I wish I had waited because I have the same complaints that your test riders had: (1) Poor gear ratios. (2) Wallowing rear suspension. (3) Bottoming that leaves rubber under my rear fender. Can you help me fix it?

   Yes and no. We have tried swapping the stock 50-tooth rear sprocket for a taller 47, 48 and 49. For big tracks we had our best luck with a 48, but were always leery about using first gear in the slow corners--because it required us to make a critical shift across neutral on the exit of the turn. For tight tracks we stuck with the 50 and and even had good luck with a 51.
    As for the rear suspension; if you are big and fast, try a 5.7 shock spring (with the rebound slowed to four clicks out). The 5.7 will help the compression damping and hold the rear end up to eliminate the wallowing, but hurt the rebound. If you are light or slow, the 5.7 solution will make the rear suspension too stiff. We have had good luck with the Pro Circuit shock linkage (like the one they use on the KX250, KX250F and KX125). It lowers the rear end, which is a good thing, and stiffens the first 220mm of the shock's stroke. Our best luck has been with a revlaved shock or Ohlins KX450 shock and the Pro Circuit link (which is what is on all the Kawasaki race bikes).

OLD WIVES TALE
Dear MXA,
    When I load my bikes on my trailer the only way I have of keeping them down tight is to compress the front forks. I hate doing this because it obviously it kills the springs. Got any ideas on what to do?

   Year ago, when fork spring metallurgy was in its infancy, fork springs would sack out from over use, but not in the last 15 years. Think of it this way, if your fork springs can take hitting the ground at 50 mph with a 200-pound rider on them, how could being pulled down a few inches by tie-downs hurt them? Cinch them down tight. It will not hurt them.

ALL HAIL ATHENA
Dear MXA,
    I have an 2006 Honda CRF450 and would like information on big-bore packages you have tested and prefer. I ride the Over-40 class in motocross, but still go pretty fast. Thanks for your help.

   Given our druthers, the MXA wrecking crew would choose the Athena 488 kit. The complete kit retails for $787.95. Call (909) 608-0082 for info.

2002 YZ250F SETTINGS
Dear MXA,
    I recently got a 2002 YZ250F. I was wondering what the best suspension settings the MXA test crew found for a 185 pound rider.

   Here are our recommendations for the 2002 YZ250F:

    (1) Geared it down. We added one tooth to the rear sprocket.

    (2) On the shock we ran the race sag at 97mm, the high-speed compression on 1 1/4 turns, the low-speed at 7 clicks out and the rebound at 11 clicks out.

    (3) For the forks we ran 14 clicks out of the compression, 12 clicks out on the rebound and slid the forks down until 5mm of fork tubes extended above the triple clamps.

CORRODING BEFORE YOUR EYES
Dear MXA.
    The foam on my Oakley goggles rots away before I'm ready to buy new goggles. The rest of the goggle is fine, but the face foam disintegrates. Any solutions?

   Yes, after every race weekend dip your goggles in a bucket of clean water. The clean water will remove the dirt and sweat that are detrimental to the foam.

GO BIG OR GO HOME
Dear MXA,
    This year the Honda CRF250 comes with a 40mm Keihin carb. Last year it had a 37mm carb. Why don't all bikes go to big carbs?

   In an age where bigger is better, a big carb is not the always the best solution. A large venturi flows more air and fuel, but at a slower velocity. This means that the engine has to turn over faster to maintain sufficient air flow to keep the fuel flowing. A smaller venturi carb flows less fuel and air, but at a higher velocity. The rule of thumb is that a big carb is best for high horsepower at a higher rpm and a smaller carb is best for snappier throttle response and better jetting at lower rpm. As for the 2006 Honda CRF250, we think that the 40mm Keihin is too big, which is why we run a 2005 carb (37mm) on our CRF250. A cheaper solution is a TBT carb stuffer, which brings the 2006's 40mm carb down to 38mm. Call TBT at (509) 941-7716. It retails for $79.95.