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stuck piston

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I just picked up a 1978 Yamaha DT125E that has a stuck piston. I've tried soaking it in penetrating oil for a week and no luck. Just wondering if anyone had their own ways of dealing with stuck pistons.

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If it is stuck because it is seized, block of wood and a hammer.

If it has seized because of sitting, and it has rusted... block of wood and a hammer.

Hope this helps 👍

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Sometimes I take the engine out of the frame and put it on the press and shove the piston out. Heat also seems to help.

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I have heard that pouring a little brake fluid in the cylinder on top of the piston, a leaving it to soak a day or so will free up a rusted in piston. However I have not had personal experience of this, try at your own risk!

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Well after 2 weeks I finally got the sucker out. I tried penetrating oil, ATF, Brake Fluid, Heat and it wouldn't budge. I finally got the block of wood and hammer out and beat on it until I got it moving. I broke the piston skirt, But since I was going to replace it anyways it wasn't a big deal. From looking at the piston and bore it looks like it was just rusted in place. Now just got to look for a new piston, rings, gaskets and a 2mm bore job on it and I'll be good to go. Figured I'll include a picture of the piston after I got it out. thanks for all the replies !

100_0117.jpg

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Hopefully you didn't get any of the debris from the broken skirt get into your bottom end.

Speaking of the bottom end...If you're hoping to just slap a new piston in there and go riding, you're asking for BIG trouble! At the very least you should flush the bottom end out, oil up all the bearings, and replace the crank seals. At most you should split the cases and replace the crank bearing, pin, thrust washers (possibly the rod) and the main bearings. Do some homework and check everything out thoroughly and make sure you won't just be throwing money away on a piston, rings and a bore/hone job for an engine that will break again in short order!

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