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I've got a 89 yamaha ovation 340. I took for a tour last winter around march break, it was quite warm that day above 0 celsius. I was riding along about 3/4 throttle when i noticed i was losing power then i heard a bang and some grinding. Once i got the heads off i saw that i melted a small divit in the left piston (furthest from fan) but the right one was fine. So it was tought that it just over heated and that none of the metal travelled down to the botom end. So i got someone to fix it. They honed one cylinder the put a new piston and rings in. So the motor was put back into the sled and it ran fine when it was tested on the spot until i took it for the first spin this year.
After about 5 minutes of riding the same thing happened. It was running really hot but when i took the heads off all that had happened was there was metal in the bottom end and it came up and scored the f**k out everything. But it was still running hot. When i tore it all down i saw that the crank seals where shot, could this be way it is running hot, causing it to lean out because it did almost melt a hole though the piston the first time. Do you think there are any carb problems because i am getting all new gaskets and seals and pistons really soon, I wanna take care of every possible problem. Also after the second run the plugs where light grey, white and bone dry
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>Originally posted by jason101:

I've got a 89 yamaha ovation 340. I took for a tour last winter around march break, it was quite warm that day above 0 celsius. I was riding along about 3/4 throttle when i noticed i was losing power then i heard a bang and some grinding. Once i got the heads off i saw that i melted a small divit in the left piston (furthest from fan) but the right one was fine. So it was tought that it just over heated and that none of the metal travelled down to the botom end. So i got someone to fix it. They honed one cylinder the put a new piston and rings in. So the motor was put back into the sled and it ran fine when it was tested on the spot until i took it for the first spin this year.
After about 5 minutes of riding the same thing happened. It was running really hot but when i took the heads off all that had happened was there was metal in the bottom end and it came up and scored the f**k out everything. But it was still running hot. When i tore it all down i saw that the crank seals where shot, could this be way it is running hot, causing it to lean out because it did almost melt a hole though the piston the first time. Do you think there are any carb problems because i am getting all new gaskets and seals and pistons really soon, I wanna take care of every possible problem. Also after the second run the plugs where light grey, white and bone dry

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Lo
It cetainly sounds like alean cond.Crank seals are probably the culprit.
I would tear down the carbs and clean em as well though.

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Also, make sure you arent running too hot of a spark plug. But if the seals were bad, that would cause a lean condition, hard starting, and probably a poor running engine. You also should take some carb cleaner and spray around all your intake seals to make sure you arent leaking air somewhere else. If it is leaking, the carb cleaner will be sucked into the engine and alter the way the sled is running.

Polaris is my way out - Other people just use a door.
 

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Do you have 2 carbs or just one??

The ovation is the 340 with the "secondary" carb system if I am not mistaken.

It definately sounds like a lean condition, or a total lack of oil. I had an exiter that had the oil pump line crack and leak causing a siezing problem where it got hot too, but never burned a piston.
 
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