This is the 2010 Yamaha YZ250F the way the MXA test crew raced it. As a rule, we don’t go for exotic or expensive mods, but if push comes to shove, we will seek competent help (no matter how much it costs). Use MXA’s mods as a guide.
Gearing:
In stock trim, the 2010 YZ250F powerband is blessed with a ferocious bottom-end, but once the engine reaches the midrange, the power falls off harder than a sorority girl on a mechanical bull. We used a taller 48-tooth rear sprocket (stock is 49) to expand the small gaps between gears. Renthal provided the stock-toothed countershaft and one tooth smaller rear sprocket, as well as a gold chain.
Graphics:
Yamaha offers the 2010 YZ250F in blue or white plastic. We opted for the rich blue look, but after a few rides we grew bored with the stock graphics. To spruce up the bike, we ordered N-Style’s Factory Issue graphics kit ($189.99). N-Style designed custom preprinted numbers to complement the graphics. For more information, visit www.n-style.com.
Front brake:
The stock front brake is so-so. As Tim Allen would say, the MXA wrecking crew was looking for “more power!” We ditched the 240mm front rotor for a beefy QTM 270mm full-floating rotor with a billet bracket ($299.00). The oversized rotor provided progressive stopping power, especially when coupled with the stock brake pads. For more info, go to www.qtmi.com.
Forks:
Heavier riders will need stiffer fork springs to keep the Kayaba SSS forks from blowing through their stroke. We swapped the stock 0.45 kg/mm springs for 0.46 kg/mm springs and found relief, but it was necessary to drain 20cc of oil out of each fork leg to minimize midstroke harshness. Lighter riders can stick with the stock springs but should lower the oil volume to erase the midstroke jolt.
Bar mounts:
A simple and cheap fix for taller riders is to move the bar mounts to the forward mounting position. Very tall riders should opt for the mounts turned forward. Most riders will find that the bar mounts turned back in the forward position are most comfortable.
Exhaust pipe:
Searching for more power in the midrange through the top-end, we ordered a Pro Circuit Ti-4R exhaust system ($999.95). Of all the YZ250F pipes we tested, the Ti-4R had the most pro-level exhaust. It traded bottom-end response for a free-revving top. The pipe passes the AMA sound test at 94.5 dB.
Miscellaneous:
We loved the Bridgestone 403A/404 tire combination that came stock on the 2010 YZ250F. Once the tread wore out, we tried the Dunlop MX51 rear with an MX31 front—this worked well in intermediate to soft terrain, but the Bridgies are better. We also used Tag Rebound grips. They have a slightly bigger squeezing diameter to accommodate larger hands.
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