Melted Pistons Question

[beeess]

I'd like to run a problem by you experts out there. I melted both pistons on a 1996 Vmax 600 this past weekend. The sled is all stock with only about 950 miles. Both melted on the exhaust side. Thought I'd better find the cause or it's gonna happen again. Any ideas as to what might have gone wrong?

[Gissert]

Are your carbs properly jetted and adjusted for the temp/altitude? That could be a cause for you unfortunate meeting of Mr. Squeaky if you are jetted to lean. Sometimes partially plugges passages can cause problems too.

How are the rubber boots that are between the carbs and the engine? If these have any cracks or tears, it will suck in air, leaning out your mixture that will burn you down.

Leaky base gaskets and pto bearing seals are another possible spot for air to suck into the crankcase, leaning down the mixture as well.

Check the oil pump for proper operation/adjustment also.

[emtbucket]

How long did you warm it up before you went out and held it wide open till it cold ceased. I know a guy that has 10,000 miles on his v-max 600. If I remember right it is cold ceased on exhaust and if it was to lean it would be on the carb side. I might be wrong but sounds like a good case of running to hard to soon. Let me know if this could have been your problem. A very expesive lesson if it is.

[WarrenA]

be sure to check the clearance between the piston and jug. years ago when i worked at a polaris dealership polaris had a clearance problem in new sleds and they would sieze on the exhaust side, as i recall they were 340 cc free air engines

[Mueske]

Did it run really well just before it melted down? If so I'd guess you sucked in extra air or for some reason not enough fuel went in, just like Gissert said. Were you on the main jets, as in more than 1/2 throttle? Had some work just been performed on the engine, allowing something to not be tightened up just right? I've never seen one squeak down both pistons at once if it were solely a jetting problem as one side will always be a little richer even with identical jetting. My $.02 worth: seek a technician to fully diagnose your problem. The answer is not to throw money (new pistons and rings) at the sled, but ensure the problem is cured. Good luck.

Kevin

[MnIceman]

Maybe a little friend (mouse) made a home in the exhaust. I've heard of them making their way all the up to the pistons. Will cause an extra high exhaust temperature until everything burns out which sometimes is to late.Could be ethanol too.
I have a "96" V-Max600XT with 4400 miles on it. I bought it from a friend in 97. Mine has the factory H.O. kit in it which was installed at 250 miles. The carbs are jetted to the max and I found that everything in the carbs were set for the max amount of gas.Supposedly there is a special head gasket and the clutch has a heavier spring. I was told to use only NON- ETHANOL PREMIUM GAS or there could be trouble by the Yamaha mechanics. I've never heard another V-Max that sounds like this one. It goes and I'm always the first one looking for gas.