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Discussion Starter · #1 ·
I have a 2001 MXZ 600 that has melted down the mag side piston twice now. first time lasted 110 miles, second time 30 miles. Plugs are nice and Tan color. Dont think its a fuel/Air leak problem I was leaning towards something with the timing. Not sure if a failing MPEM unit would cause something like that. Each time it has burned down the Clutch Side piston looks perfect only the Mag side is having issues. Each time i take the head off it looks like the top of the piston has been chewed up like something is bouncing around in there. Not sure if the MPEM is faling giving it to much timing in the higher RPMs. Just wanted to get some other opinions before i keep throwing money at it for parts it might not need. Thank you.
 

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One plug longer than another, making contact? Electrode breaking off? Sucking up a chunk of broken aluminum from the crankcase?
Wrong rings? Was the cylinder bored and the piston your using too small?

Photos would be helpful, so "we" can see what you see.
 

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Discussion Starter · #3 ·
One plug longer than another, making contact? Electrode breaking off? Sucking up a chunk of broken aluminum from the crankcase?
Wrong rings? Was the cylinder bored and the piston your using too small?

Photos would be helpful, so "we" can see what you see.
No, Plugs look perfect, used BR9ECS what the book calls for. Wasnt hitting the piston. was bored and pistons had perfect clearance on the ring and the piston to cylinder clearance. Ill try to get some pics when i can sled isnt with me at the moment
 

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Discussion Starter · #4 ·
One plug longer than another, making contact? Electrode breaking off? Sucking up a chunk of broken aluminum from the crankcase?
Wrong rings? Was the cylinder bored and the piston your using too small?

Photos would be helpful, so "we" can see what you see.
Basically mag side piston has pitting all around edge of it. Ring is still intact.
 

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if it all the way around the perimeter of the piston it leads me to believe either the heads warped or the conecting rod is damaged somehow. When the piston is TDC does the ring catch the top of the cylinder maybe?

Add a pic of the head if you can as well.
 

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No, Plugs look perfect, used BR9ECS what the book calls for. Wasnt hitting the piston. was bored and pistons had perfect clearance on the ring and the piston to cylinder clearance. Ill try to get some pics when i can sled isnt with me at the moment
From the research that I have done and looking at the spec book, your sled calls for BR9ES, not ECS, now if that is why it keeps having problems is beyond my knowledge. but I do know if you re gap ECS the strap has a large chance of breaking off just an FYI.
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Discussion Starter · #7 ·
From the research that I have done and looking at the spec book, your sled calls for BR9ES, not ECS, now if that is why it keeps having problems is beyond my knowledge. but I do know if you re gap ECS the strap has a large chance of breaking off just an FYI.
View attachment 2009801
Thanks for catching that, not 100% sure whats in there but do beleive it is the ECS. Not sure if that would cause that though same gap, heat range and reach, but will definitely check that out. I suspect something going on with the timing, going to measure it and check this weekend. Maybe an offset key and a touch to lean of a mag side carb, IDK. really scratching my head at this one.
 

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Melting indicates excess heat, not just physical damage from a piece bouncing around. I.e., detonation fits the symptoms. The measurement above sounds like advanced timing, which would be a cause of detonation.
How about the fuel? Is it old or does it smell funny?
Look very closely at the plug insulator, with a magnifying glass.. see if there are any tiny speckles or particles there.
 
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