It is always helpful to have a stock model of a bike on hand when testing a modified version, because the improvements could require a back-to-back comparison to uncover them. In the case of this White Brothers Yamaha YZ250F, I was happy to have the stocker along for another reason: I'm not sure I would have believed how much better the WB bike is than the stocker. I'm a pretty large rider, so I haven't spent much time on 250Fs lately. When I rode the stocker, I was surprised at how easy it was to get up to speed and tackle every obstacle on my track. I was up to race pace in less than a lap! These 250Fs are fun!
As fun as the stocker was, I had no thought of racing it. Then I jumped over to the modified bike! I could race this one, and I weigh almost 190 pounds! Way down low, the power doesn't pull as smoothly and trouble-free as the stocker, but in the rpm ranges in which pros, or even intermediates, ride at, this WB YZ250F hits hard and pulls strong all the way to the rev-limiter. The ignition was stock, so the rpm ceiling can't be higher than stock, but it sure feels like it is. The bike never stops pulling and never hesitates to shift right into the meat of the torque. This isn't just a more-rpm type of power, either. The engine has grunt that jerks it out of turns and throws it over jumps right out of turns. My dad thought it was a 450 while he was watching me ride!
This MB1 suspension was active and so plush it made the stock suspension feel harsh and dead. It handled every landing fine but soaked up the track chop and hack 100 percent better than stock. The price tag on the engine is more than half the cost of a new bike, and the suspension isn't budget stuff, either. But once you ride a bike like this, you'll be able to motor right past that broken piggy bank without shedding a tear.
The full parts list is available here at www.dirtrider.com.
 |  Josh Bagge is normally a 450...  Josh Bagge is normally a 450 guy, but the White Brothers Yamaha YZ250F made him think life in the Lites is possible for a heavy rider. |  |
 WB porting and pipe help it...  WB porting and pipe help it breathe. |  There are new cams and valves...  There are new cams and valves in there. |  We thought MB1 was a Showa...  We thought MB1 was a Showa place, but this suspension rocks. |
 Black rims and Dunlop tires...  Black rims and Dunlop tires handled the rear end. | 
You gotta love carbon |  Applied changed the offset...  Applied changed the offset and bar position |