Bike #103:
+1.5mm stroker, 13.5:1 high-compression
This was the most finicky of the bikes and took the most jetting and setup work to come to the finished 257cc machine. It was slower revving than the nonstroked bikes and it made a slightly more torquey pull, but not a big difference in outright power, actually feeling a bit off on top. If you're the kind of rider who likes to let the motor do the work by using the throttle and not the clutch, then this is a step in the right direction. Truthfully, all of our test riders would opt to go one step more (see bike 104) if we were going into the cases to replace the crank. There was also more vibration and harder starting than stock.
Bike #104:
+1mm bore and +1.5mm stroker, 13.5:1 high-compression
This 263cc creation was by far the strongest feeling bike, but it did not seem like it was the fastest for pro riders since it didn't rev quick enough. What it did do was give the (formerly) 250F more torque and grunt, especially at lower rpm, and the meat to pull out of the turns without the need for clutching. If you like to chug a bike but don't want the weight of a 450, then a stroked and overbored 250F is an option. This bike's power was the best on the bottom and in the mid, and even though it seemed to rev out pretty respectably for a bored and stroked bike, that wasn't where this baby liked to be ridden. This bike also wanted to lose at least a tooth on the rear sprocket to get the most out of the newfound bottom pull. And for some reason the FMF exhaust system did not help this setup. There was a little more vibration, but not as much as the 103 bike. Starting was difficult as well.