Stuck rings

[chet]

Any ideas on a 'non mechanical' method of freeing stuck 2 cycle piston rings. I don't want to take a chance of breaking them as they are obsolete. I'm hoping someone has a tried and true solvent or soak.

[sablatnic]

I have had luck with driving the piston to tdc and filling above the piston with two stroke oil and just let it stand, refilling whenever I passed by. 
After a week I started it, gave it a work out, and the rings were free. 

[Tacotodd]

Any ATF is almost completely detergent with a lil splash of petroleum & it works good for penetrating fluid. So does diesel fuel. What about one of our sponsors, Blue Creeper? They have some pretty amazed followers of it. 

Have you determined what caused them to get stuck in the first place? You don't want to be repeating this same problem later on.

[chet]

I think it's just a case of non use for a few years. It's a 4HP Evinrude that I haven't fired up in at least 10 years. It was running great when last used, but now one cylinder can only push about 20 PSI. That cylinder has been soaking in ATF for 48 hours so far, but no luck.

[Jeff]

Ive used blue creeper, actually rust reaper, to free up stuck hit and miss engines.

[Real1shepherd]

 Also could try Marvel Mystery Oil. 50/50 ATF & acetone is a rust penetrant.....assuming the acetone won't react to an aluminum piston.

Kevin

[SwampDonkey]

Blue Creeper was going to be my suggestion to. 8)

[Al_Smith]

If you have the piston out of the engine some carefully applied heat from a torch will usually free them up 
Stuck fast in the bore after some soak for a few days with a good grade of penetrating oil and using an adapter made  from  a spark plug and grease jerk will pop them loose .
The average grease gun produces around 5,000 PSI .It will either come or bleed .On a two cycle if it's stuck above the ports this method will work .On a 4 cycle as long as the valves are closed and it's not stuck top center or bottom center it will move it .You only have to move it maybe 1/8" to 1/4" to free it up FWIW I have salvaged a lot of engines most people would have given  up on .

[mike_belben]

After a wd40 or PB etc etc soak, I use a chunk of wood almost as big as the piston and plastic deadblow.   Hand sand the liners as much as you can first, blow it out, spray again, budge them, sand more, spray repeat.  If really stuck id put some heat to the piston crown let it expand/contract then oil again.

Once free soak pistons in a bucket of gas and refinish the bores with a dingleberry hone and ATF.  Not a rigid hone unless youre going oversize.  Hourglassed bores will still run fine if they have no major vertical gouges or sharp edges. But only a flex hone will touch everywhere without enlarging. Rigid hone will only touch the narrows.

[Al_Smith]

My bud Kevin AKA "cut for fun " had a piston with stuck rings he mailed me .I blocked it with hard wood in a vise so as not to harm it and used a  B bottle turbo  torch .Freed the rings, cleaned the ring grooves and mailed it back to him the next day after I received it . 
Now that doesn't always work in extreme cases .One was last summer on a rebuild of two Partner P-100 chainsaws .One looked like it had been under water in Great Salt Lake or the Pacific Ocean .Stuck tighter than a bulls behind at fly time .I popped the cylinder off with a grease gun and had to drill the rings loose 1/2" at time .I saved the piston but it took about 3 hours to do it .Saying that the saw came out okay ,lots of power in that big old 99 cc Swede . 8) 

[Al_Smith]

I've ran into some dandies .One was a stuck Allis-Chalmers model WC .Some genus pulled it stuck at 20 miles per hour and popped the clutch .Wrapped the rod around the crank shaft like a pretzel . Had to burn the rod loose and jack piston, liner and all out the top .
One of my John-Deere model A 's they did the same thing and broke a chunk off the bottom of the cylinder below the ring travel and also bent the rod .BTW a rod on a John Deere two cylinder is massive .Another rod, piston and welded the bottom of the cylinder back together .--never say die and throw in the towel