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!!!

 

The 'old' YZ490 was still made 1 year after the 250R and the WR500 (same motor, wide ratio trans) was made 2 more years after that. [img]i/expressions/face-icon-small-happy.gif[/img]

 

lmao. I'd rather have a 440cc Polaris cylinder on my R anyday than a CT 410.

 

A little birdie also told me that HPD is currently developing a Power Valve cylinder for the 400 that will be totally custom.

Now imagine that punched out to 440cc on your R Pete! Hell, imagine it on my 400!!

 

my R will actually have a 500 on it soon [img]i/expressions/face-icon-small-smile.gif[/img]

 

Must of got the big job?

 

something like that [img]i/expressions/face-icon-small-smile.gif[/img]

 

Fokker...You know from Meet the Parents...

 

I'm working on some treats for you as well BC, so you can be Fokker2

 

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.