i am running a magnum cylinder with a 83mm wiseco piston on my 07 wr 70 hour on it with no problems. just did the ringsi also had an athena on my 04 wr that i put 180 hours on it. went thur 4 piston.i you use the athena cylinder run a wiseco piston.
290 kit with a wiseco piston in it stage one intake stage 2 exhaust with a rekluse pro in my 07 wr.70 hours on it with 6 dist 36 enduros and 3 family in that time. doing the rings right now. never missed a beat