Artifact: This is a Keihin carburetor. MXA brings it to you as part of our
historical outreach program. Future generations will never see one.
A: The hate list: (1) Looks. UFO makes a complete plastics kit for the YZ250 that makes it look identical to the 2013 YZ250F. Surprisingly, even though the MXA wrecking crew doesn’t like the “edge styling” of the YZ250F, we still installed the UFO kit, because to do other- wise is to embrace the ethos of 2006. We don’t do that with cell phones, computers, cameras or any other high-tech toys. Q: WHAT DID WE LIKE? A: The like list: (1) Garage mechanic. Anybody with a nutcracker and a butter knife could rebuild the top end on a YZ250 two-stroke. Not everybody has the tools, know-how or enthusiasm to rebuild a four-stroke. ( 2) Titanium shock spring. Yamaha took the Ti shock spring off its four-stroke line several years ago, but the YZ250 still has the high-tech titanium shock spring. It would cost $650 to buy this spring from your dealer. ( 3) Suspension. You gotta love Yamaha’s SSS suspension. It is almost perfect right off the showroom floor. ( 4) Parts. Even if the YZ250 parts cost the same as their four- stroke nephews—which they don’t—there are a lot fewer of them to buy. The MXA wrecking crew doesn’t believe that two-strokes are more reliable than four-strokes—only that when unreliability rears its ugly head, a two-stroke owner spends less dough on pistons, rings and gaskets…and can put them in himself. Q: WHAT DO WE REALLY THINK? A: Do we think that the KTM 250SX is a better race bike than the YZ250? Yes. The KTM has been constantly updated, R&D money has been spent on it, and whatever KTM learned from its four-stroke development, they passed on to their two- strokes. All that said, we would have no qualms about racing a 2013 Yamaha YZ250. Not flashy, not modern, but workmanlike. ;
2013 YAMAHA YZ250
MXA YAMAHA
YZ250 TWO-STROKE
SETUP SPECS
This is how we set up our Yamaha YZ250 for racing. We offer it as a guide to help you find your own sweet spot.
KAYABA SSS FORK SETTINGS For hardcore racing, we ran this setup on the 2013 Yamaha YZ250 (stock clickers are in parentheses): Spring rate: 0.43 kg/mm Oil height: 130mm Compression: 13 clicks out Rebound: 14 clicks out Fork-leg height: 5mm up Notes: These are awesome forks, made all the more awesome by the light feel and snappy input of the engine. Obviously, if you are fast or fat, you might want to go stiffer on the fork springs, but typically, fast riders can dial in more compression (and use the crossover effect of rebound damping to get the stock fork springs to work). KAYABA SSS SHOCK SETTINGS For hardcore racing, we ran this setup on the 2013 Yamaha YZ250 (stock clickers are in parentheses): Spring rate: 4. 7 kg/mm Race sag: 100mm Hi-compression: 1-3/4 turns out (1-1/2 turns out) Lo-compression: 8 clicks out ( 13 out) Rebound: 8 clicks out ( 12 clicks out) Notes: The one thing that the KTM 250SX can’t touch on the YZ250 is its suspension. Compared to what comes on the KTM 250SX, the YZ250 has a works shock. Not only does it have a jumbo-sized, 18mm shock shaft, Kashima-coated internals and SSS damping, but it comes stock with a $650 titanium shock spring. AMA National-speed riders and heavyweight contenders will need to move up to a 5.0 kg/mm spring. YAMAHA YZ250 JETTING Here are MXA’s recommended jetting specs (when changed, stock specs are in parentheses): Mainjet: 178 Pilot jet: 50 Needle: N3EW Clip: 2nd from top Air screw: 1 turn Notes: The 2013 YZ250 jetting is on the edge—albeit the good side of the edge. If you hop up the YZ250 or add an aftermarket exhaust pipe, you will need to go to a bigger 180 or 182 mainjet. Other than that, the YZ250 jetting is basic, simple and effective. The air screw is very sensitive from a half turn to one turn out.
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