Killed my tbolt 141cc Bore kit

[Big Bird]

Started idling funny. Seen scouring through spark plug hole. This is what I found.

[2LZ]

Looks serious hot and lean. Got any air leaks anywhere?

[Big Bird]

Looks serious hot and lean. Got any air leaks anywhere?It was running great. If I go any richer I get a rich bog. Plug looks like its on the rich side too. WOT for a long time is all I can figure. Weird thing is the stock piston handled the same treatment for much longer just fine. In hotter weather without a oil cooler too. I'm kinda baffled. I thought it was something I did during install but it doesn't seem like it.

I slapped a new 141cc piston and cylinder on it tonight. Think I'm just gonna go easy on it from now on.

[XLsior]

Where's the piston warp in relation to the intake valve? Or is it perhaps close to the oil feed O'ring between the head and cylinder and oil has been getting through the gasket and causing the burning hot spot warping the piston...The only explanation for that is excessive localized heat.

[dirtbkr188]

Did you ride a lot of wheelies for long distances? I'm thinking oil starvation when the engine is almost vertical

[TxTaoRider]

I have destroyed allot of engines over the years and I dont think I've ever seen a piston like that. I've seen that area broken off but never bowed up like that. On nitrous they'll break, or melt through, but that's just weird.

[Mudflap]

I've seen many damaged pistons too but haven't seen one like that. It's interesting that the Lifan 140 (141 actually) uses a flat top piston instead of domed.

[China Rider 27]

How did that not hit the valves with that huge hump in the middle? Must be some casting flaw that responded to heat.

[Big Bird]

Where's the piston warp in relation to the intake valve? Or is it perhaps close to the oil feed O'ring between the head and cylinder and oil has been getting through the gasket and causing the burning hot spot warping the piston...The only explanation for that is excessive localized heat.It is right at the intake valve side of the piston. It warped up so far it hit the head but it was so soft it didn't do damage.

[Big Bird]

Did you ride a lot of wheelies for long distances? I'm thinking oil starvation when the engine is almost vertical
I don't do wheelies. I was never very good at them on my xr50 so I don't even try on this.

[2LZ]

It was running great. If I go any richer I get a rich bog. Plug looks like its on the rich side too. WOT for a long time is all I can figure. Weird thing is the stock piston handled the same treatment for much longer just fine. In hotter weather without a oil cooler too. I'm kinda baffled. I thought it was something I did during install but it doesn't seem like it.

I slapped a new 141cc piston and cylinder on it tonight. Think I'm just gonna go easy on it from now on.
I didn't mean to infer the jetting was off. Sometimes under high RPM's, air will pull thru a cracked vac line, bad o-ring, etc... I melted down a piston on my old Harley due to an old intake o-ring that pulled air under high RPMs. We were blasting up a long grade. Boy did I smoke out Mrs. 2LZ on her bike behind me when it let go.....

[Big Bird]

I didn't mean to infer the jetting was off. Sometimes under high RPM's, air will pull thru a cracked vac line, bad o-ring, etc... I melted down a piston on my old Harley due to an old intake o-ring that pulled air under high RPMs. We were blasting up a long grade. Boy did I smoke out Mrs. 2LZ on her bike behind me when it let go.....Not a lot of places on this motor to develop vacuum leaks. Just both sides of the intake manifold. I will check it with some carb cleaner today after I do a few break in heat cycles.

I'm wondering if the fact that it is a light weight piston if it just doesn't have the material there to dissipate the heat like the stock piston. With the higher compression and cam it is probably creating more heat than stock.

[TxTaoRider]

I suppose maybe a head gasket leak in that area could cause a lean hot spot.

[Big Bird]

I suppose maybe a head gasket leak in that area could cause a lean hot spot.
Wouldn't it blow carbon out of the leaking area though? I would think there would be some kind of residual evidence of that happening.

[TxTaoRider]

Wouldn't it blow carbon out of the leaking area though? I would think there would be some kind of residual evidence of that happening.

In the pic of the gasket, it looks shiny or different right in that area. And since the motor pulls in air and compresses it, it could suk in a little air there as well as push it out.

[Big Bird]

In the pic of the gasket, it looks shiny or different right in that area. And since the motor pulls in air and compresses it, it could suk in a little air there as well as push it out.Possible right from the timing chain area which would make it not visible from the outside.

[Big Bird]

I think you nailed it. That's right where the ring groove is pinching the ring too.

[grumpyunk]

Given the piston crown is not bare and has some carbon deposit, as does the cylinder head, I doubt you were running lean. I think you have a manufacturer defect in the alloy used when casting the piston. Yes it got hot, but there is no evidence in the image of any heat related melting. Most pistons do not distort under use. This one got hot enough to distort, but not hot enough to do any 'melt' damage. The fact that it is on the intake side is more evidence of poor alloy being used. The temperature would be slightly less as you have the 'cool' side of the cylinder head contacting the cylinder wall, vs the exhaust side, where hot gases are heating the head, and that's having some heat conduction down to the cylinder wall.
Wish the images were larger and the above two were lit a bit brighter.
tom