WHAT IS IT? Bolt-on traction control for the 2003–2011 Yamaha YZ250 two-stroke.
WHAT’S IT COST? $109.95.
CONTACT? (800) 800-2363 or www.steahlyoffroad.com.
WHAT STANDS OUT? Here’s a list of things that stand out with Steahly’s YZ250 9-ounce flywheel weight.
(1) Moments of inertia. A two-stroke can use a lighter flywheel than a four-stroke because it fires every stroke, compared to the four-stroke’s every-other-firing pattern. Two-strokes don’t have to maintain momentum while waiting for the next explosion, thus two-strokes deliver a snappier and more abrupt style of power. This hyper powerband was never a problem in the two-stroke era, but with the four-stroke’s rise to dominance, a two-stroke’s rat-a-tat-tat power delivery is foreign to riders bred on torquier, slower-revving four-strokes. That is where a flywheel weight comes into play; it can make a two-stroke feel torquier, broader and more hooked up.
(2) Horsepower. You might be tempted to think that a heavier flywheel would cost the YZ250 horsepower. Not so. It just makes each gear pull further, stronger and longer.
(3) Installation. The Steahly flywheel weight screws on to the top of the stock flywheel and can be installed in less than a half hour (without removing the stock flywheel from the engine). Steahly flywheel weights are machined from solid steel billet on computer-operated lathes for the ultimate in balance, trueness and strength. Steahly includes do-it-yourself instructions that give you two or three ways to get the flywheel nut off, even if you don’t have an impact wrench.
(4) Weight choices. Steahly’s bolt-on flywheel weights come in 9-, 11- and 13-ounce versions. MXA test riders prefer the 9-ounce weight.
WHAT’S THE SQUAWK? A small percentage of MXA test riders thought that the 9-ounce weight took away too much snap, but the majority were willing to give up the instantaneous sensation for a more hooked-up feel, which also seemed to improve the YZ250’s manners in corners.
This is a good tuning add-on for any brand of two-stroke. It improves traction on starts, rock-hard dirt and in ruts. It’s almost like having a three-stroke.