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Top end issues

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Have a 97 CR80. Used for flat/dirt track. When we purchased it, it had a custom expansion pipe designed to perform on half mile tracks. We run short track, so I picked up a Pro Circuit Platinum Pipe off Ebay. Everything looked good (no dents, cracks, etc.). Inside was fairly clean, had a minor amount of carbon at the engine side (i.e. not enough to be concerned about air flow). After using the PC pipe, for about 2-3 races, the top end (which was fresh when we bought the bike) cooked. We replaced the top end (including new cylinder). Used the PC Pipe, blew up again. Is it possible that when the pipe gets hot that some of the carbon is flaking off and being sucked back into the cylinder and causing it to fail? anyone have any experience similar to this? One thing that we noticed was that before the top end went, the bike would cut ou at WFO before we hit top end. You could nail it from low rev, but once we got over halfway, it would cut out. I noticed I could get it to the top end if I only went somewhere between 1/2 and 3/4 throttle.

I would appreciate any helpful input. And yes, this time when we rebuild, we will us the custom pipe.

Thanks

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yeah. dont lean out too much on with a new pipe. MAX 1 size lower for MJ and PJ and adjust the needle.

i alsonoticed some machining/weild particles on brand new, unfinished factory pipes. i always have to clean them out as much as mu fingers can reach and try to blow them from either side of the ends. DOMA pipes from experience. i think too with other western pipes.

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