Originally Posted by brucifer
The only problem I ran into using the 500 head is too much compression. I bought this head off of ebay understanding it to be a 600 head. It wasn't till later on when I actually began the engine assembly did I notice the smaller combustion chamber.
The piston is a JE 10.5:1 designed to run with the chamber of the XR650L head. I'm probably well over 11:1 with this head. It doesn't work with crappy Ca. 91 octane fuel. It pinged big time with anything over about half throttle.
it pinged! I estimate that engine's static compression is around 11:5:1.
If you thought it was gutsy rattling away on 91, take out a personal loan and fill it with some VP100.