evo porting

[RMgrind]

I have an 83 rm 250 , this is a non power valve motor. Iv been wondering how it would respond to porting. i ride trails mostly with some hare scrambles. the motor is stock except for an 82 head. am i going to have to settle for a narrow power band at lower rpm or can i get a true mo-better type of power.

thanks bill

 

[cujet]

That bike is so old that I cannot remember what the ports looked like. Not to mention what the dimensions are.

Still, there has been a quantum leap forward in port design, powervalved or not. Porting pro's today understand what works and why. So I would expect a quality job to result in far more power. I would assume that the port design on that bike is less than optimal. Kinda a big assumption, but I do not remember those bikes being all that fast.

Take a good look at the intake port, and whether the piston closes off the intake port. Bikes of that vintage often had left over theory from piston ported designs. If it does, there is power to be had in this area also.

Chris