can a powervalve hit the piston?

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sx-vipy

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i blew the first cylinder today....(i want to cry) i removed the powervalve to get a look a the piston without removing the head. I can see a "lip" on the powervalve like its been touched. I looked inside to the piston and could see that one the rings are s shaped :( but the piston can still move freely. Either the sleeve has been grooved or im very lucky and just need a piston ring kit. Is it possible that it touched or the ring was done and touched the power valve?
 
they can touch if the "stop" thats built in the casting of the cylinder is worn or the valve is worn. If you have a ring that gets distorted from heat of a melt down, that can easily contact the valve as theres only around .020" clearance there from the valve edge to the piston, not hard to bridge that gap with melted ring and snag the exh. valve. makes for a real mess to repair.
 
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yeah thats not alot gap...Ill be working on it tomorrow and get a better look.«Like you said maybe the seat is worn and the gap has been decreased. If it just a piston ring replacement, should i replace all three or could i get away with changing the one, that is if all compressions are within range....
 
I would say yes....100%.

How do I know? Was doing pre-season maintenance on my '01 SRX (backup sled) one year and took off the pipes...heard something rattling around inside one of the pipes. Said....hmm, maybe a rock..maybe a chipmunk got in there with and acorn or something. Flip the pipe on it's end and out pops half of a powervalve all mashed to to high holy he**. Sure enough took out all three p-valve housings and found one with just the shank part of the valve.

Put in another valve and rode the sled for 250 miles that weekend...without issues. Lucky? Yea...just a bit!

Have not tore into it yet and have no idea how it made it into the cylinder or crankcase and out the exhaust port without, at least, taking out a rod or a piston is beyond me.
 
NY AttakGT said:
I would say yes....100%.

How do I know? Was doing pre-season maintenance on my '01 SRX (backup sled) one year and took off the pipes...heard something rattling around inside one of the pipes. Said....hmm, maybe a rock..maybe a chipmunk got in there with and acorn or something. Flip the pipe on it's end and out pops half of a powervalve all mashed to to high holy he**. Sure enough took out all three p-valve housings and found one with just the shank part of the valve.

Put in another valve and rode the sled for 250 miles that weekend...without issues. Lucky? Yea...just a bit!

Have not tore into it yet and have no idea how it made it into the cylinder or crankcase and out the exhaust port without, at least, taking out a rod or a piston is beyond me.
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you should of played the mega millions that night you found that, you were one lucky sob....lol!! ;)!
 
sx-vipy said:
Could a meltdown happen from a frezzed up carb?
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sure... it could happen from alot of things, most burndowns are from low octane fuel, incorrect carb settings, dirty carbs, first ride out on stale gas from storage...hence, low octane again.
Water in gas can freeze and cause issues, but the amount of ethanol and crap added to the fuel, dont see a whole lot of that anymore.
 
Yep, seen a few PV's hit the piston. Generally comes from running with pull thru's, broken or too loose cables. The valve sits freely against the stops and over time they wear off.
 
thanks for all the help guys. I took the head off and i have a melted piston which i figure maybe did some damage to the pv. Im lucky cause there was no damage to the cylinder. Ill pass the rock in it and new piston and ring. Can get away with just doing the one or should i change all three piston and rings or atleast just the rings on the other two cylinders? should i put any oil in the crank base or is that lubed another way? Are there anything else that i should know to before starting it up. Bleed the preston but do i need to bleed the oil injection etc?

thanks a million
 
sx-vipy said:
thanks for all the help guys. I took the head off and i have a melted piston which i figure maybe did some damage to the pv. Im lucky cause there was no damage to the cylinder. Ill pass the rock in it and new piston and ring. Can get away with just doing the one or should i change all three piston and rings or atleast just the rings on the other two cylinders? should i put any oil in the crank base or is that lubed another way? Are there anything else that i should know to before starting it up. Bleed the preston but do i need to bleed the oil injection etc?

thanks a million
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Need to figure out why it burned down before you fix it, or it will do it again.
 
Yeah im sure it leaned out cause of the carb being blocked up. Ive been having alot of problems with the carbs being dirty this year and im starting to think its from where i get my gas. Ive heard others saying they have had problems too. Another reason why i think this is cause before i noticed the melted piston i checked the plug and it was completely dry so i cleaned the carb and tried to run it. It wouldnt run any better but this time the plug was wet.
 
If its torn down, for the extra couple hundred bucks, I would Mic the pistons at minmum and do the rings. Do a rub on the cylinders so the new rings seat right. If the pistons are out of spec after the Mic, replace them.
 
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