rod_b

Well, I just got my MT-12 I bought off a guy used. He said it's only been broken in but I'd have to believe that it's been through a lot more or abused. While there is a fair amount of compression, I took the engine apart and can push the piston past the top of the sleeve. Am I wrong or has this engine had it? Also, the front bearing feels gritty. I was told this engine was in an XXX-NT. Seems like maybe it got some dirt in it. Should I ask for my money back?

AMGRacer

Doesn't sound promising. The "Motorman" test is as follows:

1. Put a splash of fuel (small amount) into the exhaust port with the glow plug in place.
2. Rotate the flywheel while listening to the exhuast port.
3. As the piston closes off the exhaust port you should hear some hissing.
4. As you rotate the piston to the top of the stroke stop and hold it. It should hold compression (be totally silent no hissing) for at least 20-30 seconds.

tekrsq

If you can push the piston out of the top of the sleeve, the engine is toast. Unfortunately, that's the chance you take when buying a used engine. I never buy used engines unless it's from someone I know. That way, I know how the engine has been run.

dtm

When you mean you can push the piston out of the top do you mean when you take the cooling head off and everything else is still connected the piston goes up with no resistance to the top?

Or do you mean when you have taken the sleeve and piston out of the engine...the piston will drop right through the sleeve??

If it is the latter...your engine is pretty toasted!!!!

stefan

There is a way to bring that engine back to like new condition.
There is a thread here about piston/sleeve renewing from a guy named osrocket.
I just had three piston/sleeves done and those engines are screaming again, actually feels better than new.
Check it out, the guy's for real