Does anyone here no how i can get one of the older style CR250 cylinders to fit on my 86 trx 250r bottom end? I know ftzracing.com does it some how but im not sure how.

 

The 89 CR250 cylinder bolts on to the 86-89 trx 250r bottom end. It's the only year that does.

 

do you know how the powervalve works on the 89 because i have to know how i would be able to get it to work. I know that some powervalves are activated by exauhst pressure on a spring and some are mecanical and some run on a servo. Do you know how the 89 works?

 

88-91 CR cylinders are the same. They bolt right on. Ideally you will use a longer rod and the 86 style piston. It doesn't increase displacement but it gives a better rod/stroke ratio. A stroker crank needs different porting, but it makes a VERY strong engine.

The CR uses a mechanical powervalve so there isn't any way to get it to work on the TRX bottom. The new (post 99) CR cylinder uses an electric powervalve. I am curious as to whether you could use the Dyna igntion, which is setup with window switches, to operate the electic powervalve servo. A friend and I are considering trying this with a set of RZ cylinders on a banshee. The aftermarket powervavle cylinders are vacumm operated.

I have an FTZ ported 91 CR cylinder I am considering putting on my ATC250R. It is setup for micro sprint racing, but would make an awesome drag motor.

 

Something just dawned on me. The new CR is case induction so the cylinder can't be put on the TRX! That would be an interesting looking engine!