12 horse briggs promlems

[chevy_cow]

well i just got a lawn tractor with a 12 hp b&S engine. The guy i bought it from put new blades on it, but when he did he tipped it over for like 15 min, changed em, and then started to mow his lawn and it died, he thought he blew the engine but my dad went over there and had to turn it over by force one time, then it started up and died twice. we assumed he just got gas in the oil (he did) and that was the only thing wrong, well 2 days later we got it home the battery was completely dead from him turning it over. so we charged it up, drained oil (lots of gas), changed the oil turned it over an few times then it got caught on something(like before accept it was easy to turn back),so i turned it back tried to start it then it got caught again this happened several times until it got caught and now we cant budge it.
so what would be the best thing to do in attempts to fix it?

 

[Doc Sprocket]

I bet money on the piston being hydrolocked by oil in the cylinder. Remove spark plug and start cranking. If I'm right, a whole bunch of oil will blow out the spark plug hole. Perform this test and report back.

 

[anderkart]

 

[chevy_cow]

ok that makes sense

 

[chevy_cow]

ok i pulled out the spark plug and tried to turn it over with the black grate on top then something under that broke so it spins freely now,next we pulled off the pulley from underneath the engine and threaded a bolt into the shaft and tried spinning it with a ratchet and a bar, and an impact wrench until we thought the bolt had enough, the spark plug was oily but no oil came out, what is the next step?

 

[Russ2251]

Split the case and take a look inside.

 

[anderkart]

Russ is probably right, but you might try inserting a shiny-narrow bladed knife into the spark plug hole to use as a mirror in good light. (or a narrow broken piece of a mirror would be better) You might be able to see around inside the combustion chamber to observe if maybe a valve has dropped, or maybe is stuck way open and blocking the piston. Might be worth a quick try anyway, If that's the situation you might only need to pull the head off instead of the side cover...

Also,
I've had the piston in a couple small engines seize before, to get-em free'd up again:
Sometimes, i simply had to pour an once or so of penetrating oil down into spark plug hole,
Then angle the engine so the piston was horizontal, and let it sit overnight to penetrate.
Then I stuck the largest hard-wooden/hard plastic dowel-size possible down into the spark plug hole, and smacked the top of the piston with a hammer a few times to drive it down and free it up.

This might not be your issue and you might end up doing even more damage with this method. But then again, you might also free it up and get it running again without any further disassembly... Like I did!

 

[Doc Sprocket]

Ooh. Good thing I didn't actually place a bet. Well, I can safely say that the last six times I witnessed what you described, that's what it was...