Seized Piston

bgoates · Apr 9, 2008

Lately my motor seemed to have lost power. Today the piston seized. I took it home, took off the head and taped the piston and it came loose. Put head back on started up and minutes later seized again. I don't think it is because I'm running lean because I mixed 25:1 and spark plug, piston, and cylinder are all black. Anybody have any solutions before it seized permanently ?

Thanks

Bikeguy Joe · Apr 9, 2008

How many hours on the engine?
Excessive carbon build up? Sticking rings can cause a seizure.
Are you absolutely sure the plug itself is black? That would be too rich, not a cause for seizure.

Venice Motor Bikes · Apr 9, 2008

I would say to take the barrel off too & look at the rings & piston skirt & inside the barrel.
Look for ANYTHING that doesn't look right...how do the rod bearings feel? any exessive play?
Tell us what you find!

bgoates · Apr 9, 2008

Yes the plug is black. How do you take the barrel off ?

Venice Motor Bikes · Apr 9, 2008

With head off & the engine out of the bike, slide the barrel straight up off the piston.
You might have to (CAREFULLY)tap it loose with a rubber mallet, don't break the cooling fins!!!

bgoates · Apr 9, 2008

I got it started again and ran a few km's but kind of hesitant to take it for a good spin. Is there anything I just could spray into the cylinder to clean out all that carbon without taking everything apart ?

Bikeguy Joe · Apr 9, 2008

Yeah, see if there are any vertical marks on the cylinder liner or piston...may be a wrist pin bushing that went bad....how many hours on it?

deacon · Apr 9, 2008

Tell me you torqued the head bolts carefully.

I have a question though. If the cylinder walls are scored, wouldn't that mean the compression would be down too much for it to start at all. If so he can rule that out since it did start again.

deacon · Apr 9, 2008

I have one more question did the motor lock up when the piston seized.

bgoates · Apr 9, 2008

Yes the motor locked when piston seized and tire skidded.....I don't have a torque wrench so just tightened with a socket wrench.

If I'm running rich do I move the clip on the carb needle up or down ?

Should cylinder and piston be black as coal ?

I think my compression is still good...

Thanks for your comments.....

Pablo · Apr 9, 2008

So what kind of oil are you using and how well mixed is it?

Don't forget - if your oil is too rich it will make the engine run fuel lean.

It is possible you have a broken ring.........

deacon · Apr 9, 2008

You want to lower the needle so raise the clip up on a groove. how far down was it. Should have been in second from the top to start.

the say the piston should be a light brown color. When I sezied mine it had five minutes burn so it was like new. i would think a serious build up of carbon around the rings might seize it. But that is just a guess.

If your head gasket is leaking it might give you a problem but if it fires maybe not. When you had the head off did you turn the engine over to watch the piston move? When I tore mine down I could see the piston move past the intake port.

In my case the C clip was installed wrong and got sucked into the cylinder and jamed a ring. now that seized the engine for sure. I had to knock i loose with a hammer to get that darned clip out. then of course I broke two rings so had to order more and wait for them to show up. When I finally got it put back together and it started, i thought I was really something.

anyway you don't have any missing pieces do you. lol

bgoates · Apr 10, 2008

the needle clip is 2nd from top. fuel mix 25:1 with snowmobile oil. I put a new plug in yesterday and after 10 minutes it was black. Should I try mixing 30:1 ? Move needle to top clip ? Mix pee with it ? Or what ?

deacon · Apr 10, 2008

Sounds like a definite fuel air mix kind of thing.

Let me ask you one thing at a time.
1. how much do you have to choke it to get it to start?

I'm thinking running too rich and the engine is over heating. If that is true try moving the needle down but it might be that your needle seat is too large. But try moving it down first. Of course Norman would know more about this than me.

VincenT · Apr 10, 2008

might want to try replacing the original carbon sparkplug cable with a regular automotive copper sparkplug cable. Probably 7mm . Just unscrew the old one and replace with new. You will probably have to screw the original fitting to the top of the sparkplug since most automotive plugs use the larger connect. Also test the voltage output... a weak spark could mean an incomplete burn. Next tune up, I'm saving the wires and fitting one to the bike.

Venice Motor Bikes · Apr 10, 2008

I'm still thinking that if your piston is chewed up, that would cause low compression & burning rich! Pull the cylinder and check it... it's real easy!
The very fact that your engine seized up, means you should check it out anyway!

deacon · Apr 10, 2008

If you pull the piston check with someone here before you try to reinstall the rings. I broke mine before I learned the trick to it.

Bikeguy Joe · Apr 10, 2008

VENICE BOY said:
I'm still thinking that if your piston is chewed up, that would cause low compression & burning rich! Pull the cylinder and check it... it's real easy!
The very fact that your engine seized up, means you should check it out anyway!

I second that.

deacon · Apr 10, 2008

I say again if you pull the jug and take it off to check the piston PLEASE ask someone for directions on reinstalling it. I can not stress enough that unless you are sure you know ASK.. There is nothing hard about it but if you don't get the rings in right they will snap. I know I broke both of mine from stupidity. I was able to do it right after someone showed me how, NORMAN mentored me through it.

bgoates · Apr 10, 2008

I'm not going to pull the jug unless or until it seizes again. It seems the more I do the more problems develop. I'm crossing my fingers that it is running ok now. I am out-of-town until tomorrow night and hope that on Saturday I can give it a good spin. If it seizes again I will probably shelf it and use it as spare parts for my next project.

Seized Piston

New Member

Godfather of Motorized Bicycles

Custom Builder / Dealer/Los Angeles

New Member

Custom Builder / Dealer/Los Angeles

New Member

Godfather of Motorized Bicycles

minor bike philosopher

minor bike philosopher

New Member

Master Bike Builder & Forum Sponsor

minor bike philosopher

New Member

minor bike philosopher

New Member

Custom Builder / Dealer/Los Angeles

minor bike philosopher

Godfather of Motorized Bicycles

minor bike philosopher

New Member