Stuck Piston

[T. Cotten]

Many thanks to all that replied ! You have all given me a boat load of advice. One question about using acid. Won't that cause more rust ?
Craig

White vinegar is acid, Craig!

I go through gallons. (Or used to...)

The question becomes how to apply it.

You want it to soak somehow. And 'brooders' can still help.

....Cotten

[41craig]

Many thanks to all that replied ! You have all given me a boat load of advice. One question about using acid. Won't that cause more rust ?
Craig

[T. Cotten]

... maybe heat. Not oxy torch but heating the cylinder up to, say, 100 degrees C which is about 212 Fahrenheit..
John

"Brooder lamps" are safe and effective, Craig!

("Heat lamps" to city Folk.)

If not effective, there is little to save from the chisel anyway.

....Cotten

[cHarley32]

I have always mixed acetone with the ATF fluid with good results. 50-50 mix.

[exeric]

I've had to do this 4 times. Twice with blind bore cylinders, and twice with Honda cylinders. In every case, I made a wooden buck that would just fit in the cylinder and catch the bottom, or top of the piston. For a Honda piston, the buck needed to be relieved for the piston dome so your force was concentrated on the outer diameter of the piston. Pre-lubrication for weeks, months, or years can only help As soon as the piston moves, you're on you way to success. My only failure was with an Excelsior piston that was near the top of it's stroke in the cylinder. I did have access through the top motor mount stud hole but I just put a hole in the top of the piston. Cast iron pistons are great for old bikes but they can really lock up after decades of neglect. If I had to do it again, I would make a slide hammer puller that would put the force on the wrist pin. Good Luck !

[TechNoir]

I am no expert but I would certainly try more penetrating fluid and maybe heat. Not oxy torch but heating the cylinder up to, say, 100 degrees C which is about 212 Fahrenheit


If that doesnt free it off then I would strip the motor. Assuming that the piston is not stuck at TDC then you should be able to split the cases which would leave you with access to the piston from underneath albeit with a rod and crankshaft attached. More penetrating fluid can be applied from underneath. And then heat again.

If that still doesnt work then you could try acid which should remove the rust and might free it up.

If that doesnt work then its mechanical means which would be to cut the piston out but that would be a long way off and the last resort after trying the previous steps.

Just my thoughts though as I have never tried this.

I am sure others will have suggestions

John

[JoJo357]

Try using any cheap ATF Craig. Soak for 3-4 days, try working it in-between, repeat if stubborn. Always worked for me.

*M.A.D.*

[41craig]

I have a 1924 J motor with a stuck rear piston. I removed the front cylinder with no problems. This is a side project that I'm in no hurry to rebuild. I removed the spark plug several years ago and spray Kroil, PB Blaster, or whatever I have in my hand, into the chamber every so many months. It has cast iron pistons. Any ideas ? Or should I keep doing what I have been doing ?
Craig