Locked Engine

Yorkie

Yorkie

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I have an 850 project that has a locked motor from decades of sitting. I’ve had the bores filled with Marvel Mystery oil for a couple of weeks but no progress. What’s my next witch‘s brew to put down the bores to unlock this thing?
 
Yorkie said:
I have an 850 project that has a locked motor from decades of sitting. I’ve had the bores filled with Marvel Mystery oil for a couple of weeks but no progress. What’s my next witch‘s brew to put down the bores to unlock this thing?
Click to expand...
Diasassemble.
Rust and corrosion EXPAND.
Forget the romantic tales of weasel piss.
I've drilled pistons before to make them smaller, push out, discard, save the cylinder.

JMWO
 
My soak liquid is diesel fuel. Pull engine from frame and immersed in diesel fuel. Roll over about once a week. Have had some pretty rusted hunks that disassembled easy. Saving many studs and case threads. Have patients, It's worth the wait!
 
mean gene said:
My soak liquid is diesel fuel. Pull engine from frame and immersed in diesel fuel. Roll over about once a week. Have had some pretty rusted hunks that disassembled easy. Saving many studs and case threads. Have patients, It's worth the wait!
Click to expand...
Yes and Yes, put the motor in a drum full of diesel for a month or two and it will free up, my brother in law browed his brothers outboard motor and didn't tell him he dunked it in salt water and put it in his shed for a few months after, when the brother went to use it, it was completely frozen, he brought a new outboard motor but his other brother got hold of it and put it in a drum of diesel for a few months and it freed up and he sold it.
The longer it soaks in diesel the better as Gene says be patient but it works.

Ashley
 
You'll have to pull it apart to rebuild it anyway, so I'd head straight down that path. I bought a Triumph about 15 years ago and it was frozen/rusted solid. I eventually managed to get it apart by knocking (wood drift and very heavy hammer) the pistons far enough down in the bores that I could lift the whole cylinder assembly off the crankcases, which I then split to remove the crank. That left me with the crank and cylinder sitting on the bench. I undid the big ends and that freed the crank. The cylinder and it's very rusty bores/pistons (still with con-rods attached) then went into a tub of diesel, where they stayed for about five years (lots of other projects to play with). When I finally got around to them they were every bit as stuck as they were to start with. I ended up using a 10 ton press to press the pistons out the top of the cylinder (after cleaning all rust and nastiness above the pistons off). As concours says above, rust expends things, so when you do get it to the stage of removing the pistons remove them upwards (out the top) as it's very likely the piston will crack the liner if you force them out the bottom. All in all not a fun job, but it's all possible.
 
I would buy some dry ice and try to shrink the pistons. The combination of dry ice and acetone or ethanol can reach very low temperatures. The aluminium pistons will shrink more and quicker than cast iron barrels. When you use the freezing mixture, do not wait too long before trying to move the pistons. I would just give it long enough for the pistons to shrink, without the barrels getting really cold.
As you add the dry ice to the solvent, it will gas - that is part of the process. Do it in the cylinders - not in a separate container and pour it. You can get a cold burn. Hopefully the pistons might be down a bit.
You should be able to get a few thou of an inch clearance.
 
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I've used MMO for that purpose on several occasions and it worked well. In one case I used MMO to unfreeze pistons in a cement mixer engine that had been laying out in an open field for many years - put the MMO in one day and the next day the pistons were free. Are you sure it's the pistons that are frozen to the cyl wall rather than the crank/bearings/other components frozen? In any case, as suggested, you have to disassemble it anyway so start the disassembly and go from there.
 
mean gene said:
My soak liquid is diesel fuel. Pull engine from frame and immersed in diesel fuel. Roll over about once a week. Have had some pretty rusted hunks that disassembled easy. Saving many studs and case threads. Have patients, It's worth the wait!
Click to expand...
Gene,
I completely submerged a frozen ‘56 AJS 600 twin engine in a drum full of diesel for three months. It didn’t loosen it. The best use of that engine is a boat anchor. That said, try it.
 
The problem with taking it apart is how to get the barrel off the pistons. It's common on old 2 cylinder John Deere tractor engines being stuck after rain goes down the stack. One method that has been reported successful is to adapt a grease fitting to 14mm air fitting as used on a compression gauge. A grease gun can achieve great pressure and grease doesn't compress, so there's no danger of a sudden explosive movement. If something moves the pressure falls immediately. Back off valves to get closed and jack the barrels off the pistons.

I don't know if true or urban legend of a guy who used a SCUBA tank for pressure meeting his maker when it suddenly let loose.
 
I use "Deep Creep" with heating and cooling cycling and a few sharp taps with a light hammer and hardwood drift in between. If it doesn't break loose then wait overnight and repeat. Just keep doing this for a week or two. Have a lot of patience. It will eventually come loose without damaging anything. This worked on a compressor that sat outside for years "down the shore" in the sea air. Runs fine now. Same treatment was used on the seized electric motor.
Russ
 
Well my take is different , Since the oil is in there for awhile , get the spark plugs out and ask a big hefty fat man to put all his weight down on the kicker . Asked my Italian neighbour to do that and it freed up on the first try . I could not put enough weight into it . Ran good after too , no smoke . Your first option .
 
JimNH said:
The problem with taking it apart is how to get the barrel off the pistons. It's common on old 2 cylinder John Deere tractor engines being stuck after rain goes down the stack. One method that has been reported successful is to adapt a grease fitting to 14mm air fitting as used on a compression gauge. A grease gun can achieve great pressure and grease doesn't compress, so there's no danger of a sudden explosive movement. If something moves the pressure falls immediately. Back off valves to get closed and jack the barrels off the pistons.

I don't know if true or urban legend of a guy who used a SCUBA tank for pressure meeting his maker when it suddenly let loose.
Click to expand...
Back in the 70's when alloy air bottles first became available for Scuba diving, several people had them done with powder coating to give them a nice colour. Unfortunately, the baking to cure the powder also ruined the heat tempering of the cylinders. I remember a local dive shop where the entire wall was blown out by an exploding air bottle while it was being filled. Air at 2000psi requires _very_ careful handling.
 
Torontonian said:
Well my take is different , Since the oil is in there for awhile , get the spark plugs out and ask a big hefty fat man to put all his weight down on the kicker . Asked my Italian neighbour to do that and it freed up on the first try . I could not put enough weight into it . Ran good after too , no smoke . Your first option .
Click to expand...
Now WHAT could possibly go wrong doing that :rolleyes:
 
The kicker won't work but putting it in a gear and rocking the bike back and forth as you are sitting on it has worked for me.

The engine needed a top end teardown once free due to no compression.
 
JimNH said:
The problem with taking it apart is how to get the barrel off the pistons.
Click to expand...
If it can be be freed then fine. If not then…

Drill / burn / cut through the crown of the piston leaving some still on the rod and some still in the barrel.

There’s nothing to lose doing it this way as the motor needs a full strip anyway and the bores will need reboring anyway.
 
Fast Eddie said:
Depends whether you like rebuilding engines before or after they’ve blown up !
Click to expand...
I did it once with a gs750 Suzuki
I managed to free the engine and I tried starting it by spinning it on the starter motor with a slave battery
The results were not pretty because of the amount of rust in the cylinder walls
Plus the rings were also gummed into the pistons etc
 


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