Locked up motor

Hey guys- I got a spare motor here that was given to me be a fellow member here, internal condition is unknown. Its a 750 Maxim motor, and I figured for starters to do a compression test.
At first it wouldnt hand crank at all so I poured in some ATF & let it sit for a few days. I managed to break it loose by working it, but I can only get a 180 degree turn out of it til it hits a point it wont go any further.
Should I continue to work it, or will I risk hurting it more by forcing it? Thanks!

 

Can you look down the plug holes and see anything? Could be a stuck valve hitting a piston.

 

DON'T force it.....you may have a valve hanging up, you may have a chain guide that broke, ar a chain itself that broke......you may have any number of things. You can pull the oil pan off and take a look and see if you seen anything getting caught.

If you remove the cam caps which will allow for the springs to close all the valves, watch to see if any don't close. If they all appear to close, then try rolling through again. BUT, don't force anything.

Let us know what you find.

Dave

 

Thanks much for the responses, guys. Cant see too much looking down the holes.. I'll pull the pan & check there. I've never pulled an XJ motor completely apart, maybe I'll do this one just for practice.

 

That's a healthy way to look at it! Glad to hear you say that. As Yoda said, "You.....will......LEARRRNNNNN"

Dave F

 

I took off mine (working bike) to replace gaskets and seals.
All I can say is, if you're organized it'll work out.

OT: I did take apart an air compressor this weekend, due to a seized piston. The piston rod has seized because of low oil level. However, there is no pump, and the crank gets lubed when it hits low points.

You might take off the oil pan and see if anything has jammed the chains, but you might also have to take off the bottom case...

 

Had exactly the same symptoms with an old xj900 motor. It had sat for so long that one of the rings had rusted to the wall and after copious quantities of penetrants it broke loose , but it would only rotate to the bottom of the stroke, than back up to the rust riing on the cylinder wall, about 180 deg. Only two ways to tell, get an inspection camera in there ,or pull the heads.
You may be lucky enough to be able to shine a small torch down into the plug hole and see the wall after the piston has descended.

Cheers, Murray