melted cylinder

J

jkenosh

New member
i bought a used vmax 4 750 and one of the cylinder is compltely melted but the other 3 look good, the guy said it overheated but i cant think why it only took out 1 cylinder, what do you guys think
 

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WHISHFUL THINKING ON THE OVERHEAT. TOP OF PISTON DAMAGE LIKE THAT IS DETINATION. PROBLEY DUE TO WATER IN THE GAS OR CRAP OCTANE. THOSE CYLS PAINTED BLUE ? 3:16 (yammie tony)
 
Is that thing ported..???? Maybe a cracked cylinder causing an air leak..?? Notice the nickel plated secondary helix...That has race sled written all over it...
 
i got no idea about the sled, the cylinders are blue. Would water and poor octane just take out 1 cylinder like that? i was half expecting to see damage across all 4, but their isnt much damage on them, and im amazed by the amount of piston material left on the cylinder sides.
 
NO ALL FOUR DON,T GO OUT. LOOK , I CAN,T TELL FOR SHURE HERE WHAT HAPPENED, MOST OF THE TIME, DAMAGE TO THE TOP OF A PISTON IS DETINATION. 3:16 (yammie tony)
 
got the topend off of her and it looks like it doesnt have too much damage, it even looks like i could hone the cylinder. i still think im going to replace it though. i was wondering if it is a stock piston?
 

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WELL THAT CHANGES THINGS ALITTLE LOOKING AT THE SIDES. LEAN BURN DOWN. LET ME SAY YOU GOT AWAY WITH LITTLE CYL DAMAGE THATS PRETTY LUCKY. 3:16 (yammie tony)
 
i dont know the correct way to take it apart, i sucked out what coolant i could and then i took the cylinder off. im having trouble finding the culprit here, thought for sure it was the carb but it wasnt, they were as clean as could be.then i thought water in the gas but i siphon some in a mason jar and didnt see any water, i also cylinder number 4 is starting to get little dents in the top of the piston,i also had another question, do all vmax 4 come with that paper thin copper head gasket?
 
yeah you are probably right. i will get her rebuilt and find out. i had one more question, is it going to hurt to run 3 cylinders with whatever porting they have and than one that is different?
 
jkenosh said:
yeah you are probably right. i will get her rebuilt and find out. i had one more question, is it going to hurt to run 3 cylinders with whatever porting they have and than one that is different?
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I personally wouldn't do that if it has been ported. I would send the cylinder for repair even if it needs welding and nicasil plating. Tom
 
Dude,bring the sled to someone who knows whats going on..You are totally going to waste your money doing things the wrong way..Pay someone who knows..!!
 
If other pistons are showing signs, check the jetting in the carbs... It was probably jetted lean for drag racing, and someone may have tried to ride it as a trail sled.
 
guys thanks for all the help, im not trying to sound cheap about the porting and the used cylinder i just dont know any better, what seems like common sense to alot of you is not common sense to me because it is not common to my enviorment, ive only gotten back into snowmobiling for three years now and ive never rebuilt a motor before, so any help would be appreciated
 
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