[firehawk]

I posted on here about my 80cc gas motor i have over 46 look at my ad but no one has given me a hint of what to do.So i figer no one has had this happen to them may be you can give me you flying fild site and some one there can help me so let me no ty. This is my old add Here is what my motor is doing. When the motor is together it is so tight you can just turn it over if you losen the two half of the motor it is lose. but tighten it up and it is almost seize again, l need help please on how to fix the problem thanks Pete

[aceplant00]

When you rebuilt your MT80 what did you replace? If you put in a new ring the engine should be tight as the ring has to wear a bit to fit the cylinder. You basicly will need to rebreak the engine in. You should also check tobe sure the ring in on correctly as well. Right side up and also correct position in regards to the pin in the groove.Also groove might have gunk in it and its not letting the ring seat properly.

[Bill 6069]

Can you post pictures of the engine and the two halves that you are tightening when the motor "seizes"

It sounds like you have a split crankcase and are binding the crankshaft bearings when you clamp the halves together. There may be several reasons for this.

You should check that the bearings are properly located on the crankshaft and sit nicely in the top have of the crankcase before installing the bottom have. You should also make sure the crankshaft is not bent. Was the motor crashed? How did you remove and install the bearings?

Bill

[aspeed]

Sounds like something is twisted or interfering. Maybe some machined surfaces are not flat. I am not familiar with that motor to be more specific. You got three ? answers? now. If the piston/cyl is out and it still binds, you will be able to narrow things down to a specific part that is binding.

[Bill 6069]

I looked at your original post and say that this is a MT80. This is a two piece crankcase split front to back. When you talk about the two halves are you referring to the two crankcase halves or the crankcase and cylinder?.

[tallone66]

Peter, give some history on the engine. Was this a rebuild to freshen up or did the engine have a problem? Was ther a prop strike?? From the sound of things, you may not have the bearings seated all the way on the crank.
If there was a prop strike, you could have either a bent crank, or out of phase crank. that is easy to check as well.
The more info you can give, the better advise or suggestions you will receive.
There is a guy in the forms, he goes by the name ramjet. This dude is good, fire him a PM and I am certain he would be able to help you out.

Cheers
Derrick