1. Shock spring. Yamaha reverted to a steel shock spring in order to reduce the price tag on the 2009 Yamaha YZ250F. This was a good move for the consumer’s pocketbook, but it added 1-1/2 pounds to the bike. If you have a 2006 through 2008 YZ250F lying around, you can swap out the steel 2009 shock spring for a much lighter titanium spring (make sure to move the plastic spring clip along with the Ti spring to prevent coil binding).
Spring rate: 5.3 kg/mm
Race sag: 100mm
Hi-compression: 1-3/4 turns out (1-1/2 stock)
Lo-compression: 9 clicks out
Rebound: 8 clicks out
2. Forks. Very good forks for virtually every skill of rider (save a National Pro).
Spring rate: 0.45 kg/mm
Oil quantity: 521cc
Compression: 8 clicks out (9 stock)
Rebound: 9 clicks out (10 stock)
Fork leg height: 5mm up
3. Jetting. The jetting on the 2009 YZ250F is off slightly, but turning the fuel screw out a quarter of a turn makes the carburetion crisp. To further improve the jetting, we install an R&D Powerbowl2, which also allows us to quickly make carb changes without messing around. www.r1dean.com
Clip: 4th from top
Fuel screw: 2-1/2 turns out (2 stock)
Leak jet: 70
4. Exhaust system. In stock trim, the 2009 YZ250F exhaust system doesn’t pass the AMA’s very lax 94dB rule. Worse yet, it fails to complement the low-to-mid engine. We ditched the stocker and replaced it with an FMF Factory 4.1 exhaust system. Performance gains were found throughout the entire spread. www.fmfracing.com
5. Handlebars. Shorter and smaller riders won’t mind the ergonomics, but taller riders felt squished in the cockpit of the YZ250F. Switching to Renthal TwinWall 997 bend bars (www.renthal.com) instantly made taller riders more comfortable. Smaller riders should stick with the stock Pro Taper bars (www.protaper.com).
6. Steering head bearing. For some reason, we have encountered issues with the steering head bearing on the 2008 and 2009 YZ250Fs. Make sure to routinely clean the head tube and grease the bearing. If the front end begins to bind or become sluggish, then it’s time to replace the bearing.
7. Graphics. Yamaha’s design team is fond of making tiny changes to the graphics on their motocross bikes from year to year. So tiny, in fact, that most consumers have a hard time differentiating a new YZ250F from the previous year. To combat eye boredom, we installed DeCal Works graphics (www.decalmx.com).
9. Suspension. Yamaha’s SSS suspension is the works-bike equivalent for production racers. It is virtually perfect for the average rider.
10. Miscellaneous. We loved the stock Bridgestone 403A front tire, which was created in part with Yamaha and is a Yamaha-specific tire. This tire can be purchased at your local Yamaha dealer. We also used DeCal Works preprinted numbers (www.decalmx.com), a Twin Air filter (www.twinairusa.com) and a K&N oil filter (www.knfilters.com).