2V Jawa Speedway Engine Piston Seized

[Sidecarcrosser]

Hi All,

I have been asked if I could take a look at an old speedway engine or a guy who is restoring the bike. The engine is a ESO engine but the piston is seized solid in the bore and has been since the 1970s. The engine seized up and the rider took the engine out and replaced it and left it until now. I have tried parafin, Gizer and Gunk but to not avail. The barrel is lose but but obviously cannot be removed. I have tried a wooden block and hammer but have stopped after the blows were getting harder! Any suggestions greatly received. I have considered machining the piston away but was wondering if the is a non destructive method out there.

Thanks

Jon

[mark2]

can you bolt a plate over the barrel where the head should be ? large bolt in centre thro a welded nut with a steel pad over piston and screw down , some times a wooden block is the best way , make sure you are holding the barrel and using the weight of the engine not slaming the cases into the floor expecting the crank to turn

[chaterlea25]

HI Jon,
I have unsiezed an engine or two by seating the valves closed, (remove rockers or whatever) then fit a high pressure grease fitting to a sparkplug body, (weld or braze). heat some chassis grease and fill the cylinder/head
then fit the grease gun fitting to the spark plug hole and pump grease in to put pressure on the piston

Recently I have heard of freezing the engine cylinder /piston as the piston will shrink away from the cylinder
(cover in a plastic bag before putting it in the freezer, to mantain domestic bliss  )

HTH
John

[cardan]

Split the cases, split the flywheels, make a jig to support the bottom of the cylinder and another to push on the top of the piston (near the walls), apply all-over gentle heat, then press it out with a press. If it doesn't move, you'll have to machine it out, but at least you can do it with just the cylinder with the con rod hanging out the bottom.

Leon

[chaterlea25]

Hi, Again,
Leon,
I tried that with a Triumph 5t engine, the cylinder split when the piston got to the unfinned part above the flange  

John

[cardan]

Yep, old stuff is sometimes hard to judge. If it looks/feels like it's going to split, stop pressing and machine the piston out. Some people prefer to use an old fly press for this reason - it's too easy to put many tonnes of pressure on the job with a hydraulic press. With a fly press it's easy to get the "bloody-hell-that's-tight" feeling early on. Of course experience is the key, so if in doubt take the cylinder, with the piston and con rod stuck inside, to a trusted motor engineer and ask to have it removed. Finding the "trusted motor engineer" is another matter.

Leon

[murdo]

Several ways of removing stuck pistons, but first question is how it seized? Was it from water/condensation corrosion or from a heat seizure?
If first type, I heat olive oil (or any thin oil, even ATF is ok) hot enough to fry chips in (cooking chips optional but why not use hot oil first) and pour into cylinder and let cool before the wood and hammer. Some times have to do a couple of times before release.
If mechanical/heat seizure then melt the piston out with oxy acetylene torch to save barrel.

[Sidecarcrosser]

Thanks to all for your suggestions. I'll give a them a try and let you know how it goes

Many thanks

Jon

[Sidecarcrosser]

After many attempts I finally got it out - I put it under a press and it took 260 Tons to get it moving - unbelievable!! I set it up on blocks and put a punch on top of the piston. Piston is a write off and there is some damage to the barrel, but all the guy really wants is the cases anyway. Sad there was some damage however, it was one of the toughest jobs I've done on an engine.

Thanks to all those who offered ideas.

JB

[chaterlea25]

Hi All,
260 tons please post a picture of that press ?

Over the last few weeks I have been dismantling a 250ohv J.A.P engine that was siezed with a lot of rust in the bore, crank main bearing was also rusted so as I could not turn the crank to raise the cylinder off the case studs
I was able to remove the studs to split the cases
Then split the crank to release the rod/piston and cylinder
I filled the bore with a dilute citric acid mix an left it for a day or two, then turned the cylinder upside down and repeated the process,
A light cleaning then removed any residue
light pressure in the press on the piston to remove it 

Cheers
John

[Sidecarcrosser]

I've been cleaning the cases up and had a look at the barrel. The con rod was bent and the piston seized in the bore.  The piston has damaged the barrel also the main bearing was seized at just before tdc. Still the cases are fine which was the bit that was wantedd