September 29, 2009
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WHAT IS IT? The exact same exhaust system that Jason Lawrence used on his Yamaha YZ250F during the 2009 AMA 250 West Supercross series (when he wasn’t on probation – from the AMA, not the District Attorney).

WHAT’S IT COST? $849.99.

CONTACT? or (310) 631-4363.
WHAT’S IT DO? Most aftermarket exhaust companies offer several different exhaust systems for each model bike. Typically, they sell an affordable stainless steel exhaust, a full-race titanium system, and an exotic bank-busting carbon fiber unit. Why? It’s all about the constant struggle of wallet versus ego. Many riders cannot afford a thousand-dollar exhaust system?the cheaper systems are designed for them. Other riders want the best product that money can buy. For these connoisseurs, the exhaust manufacturers make the high-priced premium systems.

FMF is no different, except that they have added even more options. FMF sells, by our count, 14 different exhaust options for the 2009 Yamaha YZ250F. From titanium to anodized to stainless to carbon fiber to the MegaBomb, FMF has a plethora of choices for your bike.

In stock trim, the YZ250F has decent power from low-to-mid, but leaves a little to be desired from the midrange on up. Last year, the MXA wrecking crew tested FMF’s YZ250F Powercore 4 Slip-On. Slip-ons are the cheapest and simplest way to get the benefits of a race system without the cost. MXA came away impressed with the FMF slip-on. It added enough midrange to earn a solid four stars. Our sole complaint was that we yearned for more top end. Logical reasoning led us to test FMF’s complete race exhaust system for the 2009 YZ250F?the FMF Factory 4.1 (with patented MegaBomb header). Since Jason Lawrence had success with this exhaust (when he wasn’t fighting, getting suspended or throwing up), we wanted to give it a shot.

WHAT STANDS OUT? Here’s a list of things that stand out with the FMF Factory 4.1 YZ250F exhaust system (with MegaBomb header).

(1) Installation. Installing the FMF Factory 4.1 exhaust system was simple. The aftermarket exhaust uses the same bolts as the stock system, aside from two head pipe springs (which are included).

(2) Weight. Yamaha missed out on saving weight with the 2009 YZ250F when they reverted to a steel shock spring in place of the previous titanium spring. The steel shock spring added 1-1/2 pounds to the 2009 YZ250F. The FMF Factory 4.1 system got some of it back. The full titanium exhaust weighs 5.75 pounds compared to the 6.25 pound stocker. Nice!

(3) Performance. In stock trim, the 2009 YZ250F engine does its best work from 6500 rpm to 8200 rpm. The Factory 4.1 exhaust system worked its magic in the same powerband range. It improved the low-to-mid power and lengthened the pull across the middle. This is a great exhaust for anyone looking to boost the power without changing the personality of the 2009 YZ250F. It does not turn the YZ250F from a low-to-mid engine into a mid-and-up engine. Every pro-level test rider still wanted more top.

(4) Sound. We tested the FMF Factory 4.1 exhaust with a MegaBomb resonance chamber head pipe. Why? Aside from improving power, the chamber also reduces sound by as much as 1-1/2 decibels. Every test rider noticed how much quieter the FMF system was around the track. We applaud the FMF crew for making a concerted effort to reduce sound levels.

(5) Place of manufacture. The FMF Factory 4.1 YZ250F exhaust is made in Rancho Dominguez, California.

WHAT’S THE SQUAWK? If you are a rev ranger, then the YZ250F is not for you. Even the addition of the FMF Factory 4.1 YZ250F exhaust system couldn’t make the Yamaha engine do what it doesn’t want to do.

This is a perfect exhaust system for Novice and Vet riders. It is at its very best on tight, Supercross-style tracks where a premium is placed on immediate and potent power?which is why Jason Lawrence used it during his aborted AMA 250 West run.


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