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Thread: Stuck Piston

  1. #1
    Join Date
    Nov 2010
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    281

    Default Stuck Piston

    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

  2. #2
    Join Date
    Feb 2016
    Posts
    637

    Default

    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.*

  3. #3
    Join Date
    Dec 2015
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    Blighty
    Posts
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    Default

    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

  4. #4
    Join Date
    Sep 2005
    Location
    Sarasota, Florida
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    4,398

    Default

    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 !
    Eric Smith
    AMCA #886

  5. #5

    Default

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

  6. #6
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    4,827

    Default

    Quote Originally Posted by TechNoir View Post
    ... 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
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  7. #7
    Join Date
    Nov 2010
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    281

    Default

    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

  8. #8
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
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    Default

    Quote Originally Posted by 41craig View Post
    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
    Attached Images Attached Images
    Last edited by T. Cotten; 05-15-2020 at 11:27 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  9. #9
    Join Date
    Nov 2010
    Posts
    281

    Default

    Thanks Tom !

    P.S. That lamp looks like it came from Frankenstein's lab !
    Craig

  10. #10
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
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    Default

    Quote Originally Posted by 41craig View Post
    Thanks Tom !

    P.S. That lamp looks like it came from Frankenstein's lab !
    Craig
    Yes, Craig!

    The bulb's socket threads came loose, so it was wired up direct, goobered with silicone, and suspended with Fisher lattice clamps. The stand itself is as I found it, and I have no idea of its original purpose.

    That was perhaps three decades ago, and has endured almost daily use until quite recently.

    One would think vibration would have gotten to the element by now,... but,.. it's ALIVE!

    ....Cotten
    Last edited by T. Cotten; 05-15-2020 at 12:07 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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