Yes, I had to use a socket extension to hammer the piston out of the cylinder....lol
The darker circle on the crown seems to have been the hot spot.
My guess is low octane gas.
The under side of the piston has melting showing too.
Guess why this TS760 piston melted?
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Yes, I had to use a socket extension to hammer the piston out of the cylinder....lol
The darker circle on the crown seems to have been the hot spot.
My guess is low octane gas.
The under side of the piston has melting showing too.
Bought a 2 stroke bike with the same pattern.
I figured very old gas and a big guy on the bike on a hot day on a big hill.
I figured very old gas and a big guy on the bike on a hot day on a big hill.
Nice paperweight. Pre ignition (advanced) or not enough oil in the mix.
KostasVolos
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The piston crown started to melt directly underneath the spark plug .The spark plug was unable to transfer it's own thermal load to the cylinder .Because the cylinder was unable to be cooled efficiently .
Cylinder fins packed with solidified oil ,sawdust and wood chips.
This caused extreme heat build up and lead to detonation and
lubrication breakdown .
Either that ,or the engine was over-revved and not for just a short while .
Cylinder fins packed with solidified oil ,sawdust and wood chips.
This caused extreme heat build up and lead to detonation and
lubrication breakdown .
Either that ,or the engine was over-revved and not for just a short while .
cut offs get coated with concrete dust insulating the cylinder, air filter and cases causing repeating overheats and lean conditions until it gets seized....fkers know the thing is fried yet pull out the either to get it started on high idle...
I torqued the stud nuts to 13lbs.
It's a 6mm fine thread 8.8 grade nuts and stud.
That's a lot for a 6" long stud.
They were considerably looser when I removed them.
Strange.
They do have the correct lock washers.
lets see a pic of the crank..wondering how blue it is
It got hot. The real tech will now diagnose why.
Funny, I had the same thing on the bench a few months ago. Old fuel, over rev due to small wheel, air leak at cylinder gasket. Throw in age and you have too much heat.
Funny, I had the same thing on the bench a few months ago. Old fuel, over rev due to small wheel, air leak at cylinder gasket. Throw in age and you have too much heat.
It got too cold or too hot.
Bad fossil fuel.
Electric saws will not do that.
Bad fossil fuel.
Electric saws will not do that.
Plug of the wrong heat range. I once bought a Yamaha RD350 and holed both pistons on the ride home. The original owner had just replaced the plugs with lawnmower plugs or something thinking he was doing me a favor.
Here’s what it looks like when the fuel injector get clogged and temps start to rise in the combustion chamber on an aircraft engine. The piston is 3/4” thick at its crown.
The RD350 pistons looked just like the one above. But got that way from a different reason. Mechanic at the time said it was the wrong heat range plug caused it to melt the piston. Little silver balls everywhere.
Here’s what it looks like when the fuel injector get clogged and temps start to rise in the combustion chamber on an aircraft engine. The piston is 3/4” thick at its crown.
The RD350 pistons looked just like the one above. But got that way from a different reason. Mechanic at the time said it was the wrong heat range plug caused it to melt the piston. Little silver balls everywhere.
I had a neighbor years ago that cooked a new Wild Thing after a hurricane in a couple of days from over-revving it due to a dull chain. He moved back to New Yawk a while later. I do not miss the suburbs.
So the consensus is heat in this case?
So the consensus is heat in this case?
You know , after looking over the pics again, and seeing how the whole piston was cooked leads me to believe that it was just overheated, saw probably looked a lot like the one in the pic above. The piston crown appears to have gotten soft just below the plug, but I don’t think plug heat range had anything to do with it.
It could have been many things. Water ladden fuel will do the same thing if you take out enough of the light ends. Pistons with pitting are usually subjected to detonation or even just too much water entering the combustion area under a severe lean condition. Three seconds or less is about all you get on a drag strip with a 3500lb car running a V8. Usually by the time you hear "jinglebells" the piston has already dropped or outright failed. When the flames come out of your valve cover breathers or blow the valve covers off it's a good bet that sparkys got too hot. Where does thing all the heat go in the saw that passes the piston? Yup, right back in the case.
Boats will score a hole in a piston just from too much load on launch trying to get up on plane. That is normally a serverly advanced ignition lead time and poor fuel quality. Two stroke outboards are more prone to it but with modern igntion retard electronics and knock sensors it gets covered up most times. Pre-ignition from carbon deposits causes the depression once the piston starts approaching its melting point. When the flame fronts collide the weak point fails from shock waves across the piston dome. Sometimes they crack at the pin wall or the skirt interface area. Nothing good ever happens after that. Sometimes I find tiny holes around the quench area with material just gone. Apparently aluminum is a good fuel when heated enough.
Boats will score a hole in a piston just from too much load on launch trying to get up on plane. That is normally a serverly advanced ignition lead time and poor fuel quality. Two stroke outboards are more prone to it but with modern igntion retard electronics and knock sensors it gets covered up most times. Pre-ignition from carbon deposits causes the depression once the piston starts approaching its melting point. When the flame fronts collide the weak point fails from shock waves across the piston dome. Sometimes they crack at the pin wall or the skirt interface area. Nothing good ever happens after that. Sometimes I find tiny holes around the quench area with material just gone. Apparently aluminum is a good fuel when heated enough.
