hey, after i put my new expansion chamber on it, i took it for a spin, it took about 100m to start (kick over) and then it went, but 2 hours later i went to start it, started first go, then 20 mins later it just stopped, i was cruising about 40kmh and im still in break in, probs on start of 4th tank with 16:1. I have a spark and compression, and fuel goin to the engine, there are no leaks anywhere where it should be taking in extra air to make it lean. its running rich. and now it just wont start, but this cant have anything to do with the exhaust can it? im having a look at the piston tonight , im taking the top head off to see if the piston is still all there in top condition! Much Appreciate any help! Thanks!