Frozen Motor

I just got a 1975 850 Mk III, the motor is frozen. I have removed the plugs and filled the cylinders with marvel mystery oil and will let it soak for a while. My question is short of a total rebuild of the engine is there anything else that I can try to free up the engine? I will be doing a complete rebuild on this bike but would like to get the engine freed up first.

Thanks,
John

This is how I freed up a Triumph engine recently. Soaked it for 3 days and it wouldn't budge.

This worked a trick. Bolt is a carriage bolt.

Had to bore it and put new pistons in the motor because cylinder was scored.

I used an old spark plug with the ceramic removed and an air fitting for a compressor attachment brazed on the top. I screw it into the head and let the air pressurize the oil through the rings. When I went to the other side and did the same the engine freed itself.
Edit: You will have to take the head off and remove the pushrods as one set will be on the cam lobes.
Best of luck
cheers,
Thomas
CNN

Some of the antique tractor guys use this trick for the really stubborn ones:

They adapt a 1/8" pipe thread grease fitting to an air hold, you can make one yourself by beating the ceramic out of a spark plug as mentioned above or simply buy one at the auto parts store, and, ensuring the valves are closed, just pump the grease gun until it either moves or doesn't. If it doesn't you've got real problems as even a hand grease gun can produce a lot of pressure. You may have to loosen the valve adjustments if it happened to stop with a valve open in both cylinders.

The tractor guys will do everything they can to get one unstuck even if they're going to do a complete overhaul because, as you can imagine, it's really difficult to disassemble a stuck engine.

I bought an old two cylinder John Deere as a parts tractor. It was stuck but, like you, I filled the cylinders with a penetrating oil and left it for a while. One day while prying on the starter ring gear it moved. I put a mag and carburetor on it and it ran great! Once I ran it for a bit I looked in the cylinders with a borescope and it was like new, just a small line where it had been stopped. I ran that tractor for years and just sold it a couple of years ago.

I wouldn't try anything before removing the primary drive to eliminate the possibility that the transmission is in play, then checking the camchain/path for issues.

I have freed up a frozen outbourd motor that was submerged in salt water from my young brother in law that he got a lend of from his other brother and when he returned it he didn't tell his brother it had been dunked and it sat for a few months, when his brother went to use it, it was frozen tight, then he found out the truth, he brought a new motor and I ended up with the old one, I submerged it in a drun of diesel for a week or 2 and it freed up and was able to get it going again which I sold for good price.

Ashley

marvel M oil (MMO) + acetone at 50/50 works better than straight MMO

I watched an old junk yard dog pour Marvel Mystery Oil over a Ford 6 cylinder with multiple stuck valves as the engine was gasping to run. Within a few minutes they had all freed up and she was purring like a kitten. Never forgotten that.