I have a question for anyone that knows about air cooled 4-strokes. I have a 300ex motor that I put a +2mm Arias piston in. It ran fine all summer and then when I was just cruising down a trail in 4th gear, the sleeve actually broke away from it's top ring, came down with the piston, and shattered upon hitting the crank. I've never had any trouble with any Honda engines that wasn't my own fault(improper installation). Did I do something wrong here?? I would think that if this was going to happen, it would happen when I was hammering on it...Not just cruising.

Any opinions?