MXA TECH SPEC: 10 THINGS ABOUT THE 2020 YAMAHA YZ250 TWO-STROKE
(1) Age. Unlike other Japanese manufacturers, Yamaha continues to make two-stroke motocross bikes. That’s the good news, but you can list the changes to the YZ250 since 2006 on a Post-It note. Here is the complete list. The YZ250 had titanium shock springs from 2006 to 2012. It got an N3EW needle and oversized bars in 2007. In 2008, it got removable bar mounts, a smaller front brake caliper and wave-style rotors. For 2011, it got a 75mm-longer silencer and less compression. In 2013, the YZ250 received a white rear fender. In 2014, the blue rear fender returned. The big change to the YZ250 in 2015 was the arrow-style plastic. For 2016, the YZ250 got black rims. The 2017 YZ250 was graced with a 270mm front brake rotor. For 2018, the YZ250’s black rims turned blue. Paradoxically, perhaps the lack of R&D investment is what has kept the YZ250 alive.
(3) Power. The 2020 KTM 250SX has as much as 4 horsepower more than the 2020 YZ250 in the midrange; however, there is easy power to be found in the YZ250 engine. Every YZ250 owner knows that a Pro Circuit or FMF pipe, Boyesen or Moto Tassinari reed cage and Mitch Payton touch-up on the ports can add beaucoup power to the blue warhorse. It’s not that the YZ250 powerband isn’t good enough; it’s just that it could be so much better from the factory. The orange deuce-and-a-half has a low-to-mid powerband, while the YZ250 has a mid-to-top powerband. The saving grace for the Yamaha YZ250 engine in comparison to the KTM engine is that it has a broader, more manageable and easier-to-use power delivery than the KTM.
(4) New old stock. The 2020 YZ250 still uses the small 22mm rear axle and has the rear shock linkage pivot bolt routed through the swingarm, while the Yamaha four-strokes use an under-slung shock linkage, 25mm rear axle, and a swingarm that is 4 percent less rigid vertically, 5 percent less rigid in twist, 8 percent more rigid horizontally and 12.2 ounces lighter. The total savings in unsprung weight is 1 pound, 5 ounces—weight that the YZ250 could stand to lose.
(5) Inertia. Many YZ250 racers add 9-ounce flywheel weights to their engines to spread out the power, improve traction and add a little extra over-rev. Yamaha could easily change the flywheel inertia at the cranks to achieve the same thing or just mount a heavier stock flywheel.
(6) Gearing. Yamaha should put a 51-tooth sprocket on every YZ250. It is the most common racer mod. Why? Because the upshift from second to third needs help. In a perfect world, Yamaha would move third gear closer to second (as they did on the YZ250X off-road gearbox). Until then, a 51-tooth rear sprocket is the hot setup.
(7) Maintenance. It doesn’t take a mechanical genius to keep a YZ250 running. Changing a top end on a two-stroke is cheap and easy compared to a four-stroke, made all the more affordable by the fact that you can do it yourself.
(8) Suspension. In what was an Edison light-bulb moment back in 2006, Kayaba switched the YZ250 forks from 70-percent position-sensitive damping to 90-percent speed-sensitive damping. It became the Holy Grail of motocross suspension. All following Yamaha forks (2006 to 2020) have benefited from Yamaha’s Speed-Sensitive System’s (SSS) linear damping. There are no hills or valleys in the SSS damping curve. It gets stiffer at the exact same rate in the first half of the travel as in the second half. Over the years, Yamaha has made damping and spring changes to keep up with the times, but Yamaha has been careful not to mess with success. If you are a fast Pro, jumbo-sized 6-footer or anemic 130-pounder, you might need to work on the YZ250’s suspension; but, for everyone else, the Kayaba SSS suspension is in a class by itself. Leave it alone and spend your time learning what the clickers actually do.
(9) Clutch. We always order stiffer clutch springs for our Yamaha YZ250s, but we don’t always use them—or rather we don’t always use all of them. You can run a complete set of stiffer clutch springs for better hookup, or mix and match the stock and aftermarket clutch springs to fine tune the feel.
(10) Common sense. The best advice we can give you about the Yamaha YZ250 two-stroke is to buy it, ride it and forget it. This is the do-it-all bike for the average racer. It is inexpensive (especially if you buy an almost identical used one), simple to repair and a blast to race.