Killed my tbolt 141cc Bore kit

Big Bird · 05-05-2021, 06:42 PM

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

2LZ · 05-06-2021, 12:30 AM

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

Big Bird · 05-06-2021, 02:04 AM

Quote:

Originally Posted by 2LZ

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.

2LZ · 05-06-2021, 12:42 PM

Quote:

Originally Posted by Big Bird

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 · 05-06-2021, 01:45 PM

Quote:

Originally Posted by 2LZ

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.

XLsior · 05-06-2021, 03:08 AM

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.

Big Bird · 05-06-2021, 11:13 AM

Quote:

Originally Posted by 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.

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.

dirtbkr188 · 05-06-2021, 07:55 AM

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

Big Bird · 05-06-2021, 11:15 AM

Quote:

Originally Posted by dirtbkr188

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.

TxTaoRider · 05-06-2021, 09:13 AM

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 · 05-06-2021, 10:22 AM

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 · 05-06-2021, 10:44 AM

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

TxTaoRider · 05-06-2021, 02:30 PM

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

Big Bird · 05-06-2021, 02:46 PM

Quote:

Originally Posted by TxTaoRider

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 · 05-06-2021, 02:58 PM

Quote:

Originally Posted by Big Bird

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.

05-06-2021, 12:30 AM	#2
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,112	Looks serious hot and lean. Got any air leaks anywhere? __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
	1

05-06-2021, 09:13 AM	#10
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	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. __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
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05-06-2021, 02:30 PM	#13
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	I suppose maybe a head gasket leak in that area could cause a lean hot spot. __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
	1

05-06-2021, 03:08 AM	#6
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,407	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.
	2

05-06-2021, 07:55 AM	#8
dirtbkr188 Join Date: Aug 2009 Posts: 564	Did you ride a lot of wheelies for long distances? I'm thinking oil starvation when the engine is almost vertical
	2

05-06-2021, 10:22 AM	#11
Mudflap Join Date: Sep 2014 Posts: 1,913	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.
	1

05-06-2021, 10:44 AM	#12
China Rider 27 Join Date: Dec 2018 Location: PNW Posts: 983	How did that not hit the valves with that huge hump in the middle? Must be some casting flaw that responded to heat.
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