Any suggestions for freeing stuck pistons in cylinder

[fasterzx]

Hi All , I am restoring a 1979 GS 1000 S . The bike has been sitting a very long time , since like 1982 ( still had gas in the tank from then ) I knew there would be some issues but not the one that brought me to a halt. It had an old RC eng. pipe that was pretty much completely rusted off. I knew the motor was locked so I started putting Rust penetrate down the plug holes a couple months ago although a lot of it just ran out what was left of the head pipes. So I tried rocking the rear wheel with it in gear - wont budge. Tried the big nut on end of crank , don't want to break the end of crank off but still wont budge. Pulled the head off , more rust penetrate. #2 & 3 cylinders are at TDC. Head & cams look really good. Thought maybe I could pry cylinder off but not many pry points without messing up mating surface on crankcase - wont budge . Tried heating everything up with blow torch and sacrificing cylinder by using sledge hammer - still won't budge. Anyone have any ideas or have a spare motor they want to sell ?

[unfocused]

I freed up a 550 just a couple of months ago. Cylinder head off, PB Blaster and a dead blow hammer tapping on the piston while trying to raise the jugs. It took some time but it worked.

[Big Block]

Diesel fuel can work to free them up. Don't be in a hurry, let it soak for awhile. Problem probably is being at TDC it's hard to get enough liquid to sit all around the piston. You might start looking for a cylinder case though. I imagine it is still in the bike so you can't tilt up the engine to get the liquid to sit all around?

[slayer61]

Diesel fuel, PB Blaster... I like Kroil and lots & lots of patience.

[GregT]

ATF and acetone 50/50 plus soak time and patience. Recently freed off a rusted solid 2 stroke with this mix.
And i'd lift the front of the GS so the cylinders are vertical. Better soaking all round the pistons.

[Cipher]

Hi All , I am restoring a 1979 GS 1000 S . The bike has been sitting a very long time , since like 1982 ( still had gas in the tank from then ) I knew there would be some issues but not the one that brought me to a halt. It had an old RC eng. pipe that was pretty much completely rusted off. I knew the motor was locked so I started putting Rust penetrate down the plug holes a couple months ago although a lot of it just ran out what was left of the head pipes. So I tried rocking the rear wheel with it in gear - wont budge. Tried the big nut on end of crank , don't want to break the end of crank off but still wont budge. Pulled the head off , more rust penetrate. #2 & 3 cylinders are at TDC. Head & cams look really good. Thought maybe I could pry cylinder off but not many pry points without messing up mating surface on crankcase - wont budge . Tried heating everything up with blow torch and sacrificing cylinder by using sledge hammer - still won't budge. Anyone have any ideas or have a spare motor they want to sell ?

if its feasible try the rear wheel trick again but go through the motions of a bump start. Far more energy input that way. Do be ready on the clutch if the tire breaks loose.

[fasterzx]

It is definitely is stuck with rust. Doesn't look that bad to me, Don't think a picture would show much. So started probably 3 months ago with PB Blaster sprayed down the plug holes. Didn't realize pistons 2 & 3 were at TDC until I got the head off. What ever I put in the cylinders does disappear after a while. #3 is the slowest to drain. After posting I tried a couple of the suggestions. I put the front wheel on the lift and raised it to level the engine as the PB Blaster was pooling at the front of the cylinders. Tried a mixture of diesel and Marvel oil and let that sit a couple days and back to the sledgehammer - no luck. More soaking for a day and then Tiki torch wicks soaked in kerosene burning on top of the pistons for an hour or so - more sledgehammer. Tried a gear puller after that with the bolt on top of the piston . Still won't budge , not even a little. Somebody mentioned patience but I guess at this point I have ran out of it. The bike is pretty much all original unmolested other than the pipe as far as I can tell and I was hoping to keep and rebuild the original engine. But at this point I have all the body work painted ( came out excellent ) staring me in the face. I have ordered another engine supposedly from a 7500 mile runner when pulled. I'll set this engine aside and keep pouring stuff in but when I read stories of stuck tractor motors taking 2 to 3 years to unstick I might not have that long. Thanks for all the suggestions.

[rphillips]

I've un-locked 2 Honda single cam 750 engines by putting eng. in 5th gear and sitting on bike, on both wheels, just keep rocking back and forth, your weight on the bike will help keep tire from slipping and having in 5th gear will put a lot more gearing pressure to rotate the eng.

[Big Block]

You're doing the right thing. I'd do the same. Get it running but don't get rid of the original engine. You can work the original over later.

[pedroA]

Hello, I have a 1980 gs550 motorcycle. I put pistons at 63 mm and I am now working on the cylinder cover and I need recommendations for the modifications I have to make and at how many degrees do I have to run the crankshaft?

[rphillips]

First Welcome, Now, sorry but I'm not understanding the questions, I don't see piston dia. affecting head cover at all. Nor am I understanding crankshaft degrees, crankshaft got to go 360 degrees. Also I wouldn't think a 63mm piston would fit in a 550.

[pedroA]

I put the cylinders of the 650 and I tried the engine already and it walks very well but I want to give it a little better performance by moving the degrees of the crankshaft to power a better opening in the intake cams

[Rich82GS750TZ]

pedroA, your issues have nothing to do with the topic of this thread. I would recommend you delete your comments here and start your own, appropriately titled thread, then ask your questions.

[rphillips]

Yes, should be a pretty interesting thread.

[P09luis]

Kroil oil or Marvel Mystery oil has worked for me.