stuck motor old briggs

well i found a cool old motor it's a wmb briggs and stratton made in '57(think thats
what the tag said).
i have gotton the crank freed but the piston won't budge all i can do is rock the crank back and
forth a little.so i was wondering what the best thing to try to free it with is

hoping to put it on a bike on a website it says 1/2 hp but it was probably rated pretty modestly
and with a better carb should put out 1-1 1/2 hp in todays rating

If your crankshaft moves and your piston doesn't sounds like your rod is broken.H.D.

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You never know what you might know,you know

Motor
Try some Marvel Mystry oil down the sparkplug hole. I bought an 8n tractor with all 4 pistons stuck, used the MMO let it sit for 24 hrs tried to move it, no go. Added some more and 24hrs later it came free. The folks on the 8n board swear by it and have seen several posts where it worked on stuck tractor engines. Can't hurt to try it.
Elmo

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All times wasted wots not spent ridin

no it's all pulled apart the piston is on top center so the crank rocks back and forth a tiny bit
will try marvel oil

I have a 1948 WMB. What carb have you considered? The vacuum carb on there isn't good for much........ and there is no real throttle. They were designed to operated at more or less one RPM to power washers, etc.
Mine wouldn't run as the valves were stuck open from carbon. Runs now but again that carb won't allow easy starting without considerable priming.
I have read it is actually rated at 5/8 HP. With it's design, it has more torque than an equivalent Chinese 2-stroke. Could work on a belt driven machine - my plan.
I did read about the carb swap but can't remember what might work. Do you know?
Let me know,
Dave
KC

i had an old suzuki RV90 trail bike that i got with a seized piston. with the head off, i just poured some regular motor oil in the top, till it filled up. let it sit for awhile, and the oil seeped in and loosened it up.

same deal with the mystery oil, but cheaper.

I have had excellent results soaking the piston/ cylinder with straight diesel fuel. I have read that a 50/50 mixture of diesel fuel and kerosene works better yet.

the best penatraiting oil ive ever used was pb blaster....soak it in it....by the way it might be a blessing....they make bigger cranks and cams for these and ive built these to run alcohol...wapwap...funfun

Auto trans fluid, PB Blaster, or Liquid wrench......and time (the key ingredient) will get it loose.

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If it ain't broke, and you mess with it long enough, it will be.

i realy haven't given alot of thought about a carb to put on it only thing i can think of for a
motor this small would be the carb from a weedeater,the carb on it is no good
if i can free it then it will probably have to be belt driven