the 85-86 bikes dont have power valves, the 87s have a 5 bolt intake manifold. the 88 to 92s have a 6 bolt intake manifold. that should help a little with the year. those bikes also had a problem with crank seals blowing out. so you may wanna split the cases. i had an 87 that was ported, piped, and all that great stuff. it was pretty dam fast, but it kinda broke a lot. it always had some kinda of weird problem. mine had 150psi with a shaved head so 120 sounds right. hope this helps.