Any thoughts on whether this will work? The exhaust valves/ power valves, on my 87 rm 250 packed up on me last spring. Cost to replace and repair them, and the piston and sleeve is gonna be about $1000.00 Cdn. Obviously not worth it as I have a 91Cr 500 in the picture now. A freind of mine that is fairly mechanical suggested that I look into the possibility of resleeving it with a 85 sleeve, as they did not have the power valves then. This would be about a 300.00 fix, Would this work, or am I now the proud owner of a yellow pile of crap? Any other suggestions?