Polaris 400 on 250r??
#31
Plus, there are aftermarket heads for the Polaris cylinder: billet alum. that can be girdled through the cooling fins and bolted directly to the case, o-ring sealed with inter-changable domes up to 15:1 compression, and big bore kits available up to 425cc (remember the OE displacment is 378cc), using pistons from old YZ490's!!!
#34
#40
Classroom, The quickest way from point A to point B is with displacement. If this isnt true way are all these hi-performance shops installing Polaris and Pilot cylinders on the 250R cases? i.e. MP racing and Dennis Packard. The powervalve is a way to make the smaller "big bore" cylinders do what a realy big bore cylinder does by itself, build torque. Dill, your on the right track with a 500cc setup.