Originally Posted by dnrobertson
I moved to a Wossner piston (due to a inlet cam follower bearing failure that wrecked a lot of the top end) about two years ago. 2005 640A.
Before the swap, the bike would "walk" across the garage on fast idle.
After the swap, the bike would still "walk" across the garage on fast idle, but I thought it was smoother whilst actually riding it.
Shortly after the first top end rebuild, I had an exhaust follower snap that totally destroyed the top end and required a total engine dis-assembly (coolant through motor). I believe the engine rebuild (by a very good KTM mechanic) resulted in a smoother bike than the piston alone.
So, my summary: If you need a new piston go the Wossner route, but I don't think it's worth the cost and hassle on it's own. YMMV
I just put in a stock piston and my bike doesn't walk across the floor.
Maybe it was just Doug at Motosports in Des Moines Iowa that helped when he did the rebuild. Not necessarily the piston itself.
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