I have been fiddling with my JD gt 275 for the last year or so,restoring it. Its been a project of...a little here and a little there as I've got a lot on my plate. I finally got to the point of being able to start her up...except it wasnt starting. I thought a minute, and realized the gas was over a year old. So...seeing as how I just couldnt wait , I decided to squirt a little fresh gas into the carb. It spun a few times....and then POW! and then flames out of the carb....arrrggh.....RUN!.....then RUN back ....then RUN some more. Dangit...where is something to put this out? oh...here come the wife with a wet towel. So I grab that and throw it over the carb. whew...thank god my wife was giving the puppy dog a bath! So...I survey the damage. Nothing bad at first, the filter is toast, alittle melting of the filter housing. But then I see it....the muffler is blown and separated at the seams! Dang...? I then realize the compression seemed to be gone some too. Uh-oh.....I'm thinking it may have got the piston. Dang-it....dang-it...foot! This is a low hour Kawasaki 17hp engine, with maybe 250 hours on it. All because I was too lazy to drain the old gas out. I'll start the disassembly later this week. I've got to get my taxes done......dang it:flag_of_truce:
You think it took out the piston? Wow, that would be a huge amount of fuel. Have you checked the valves? I would think a valve could get damaged before a piston let loose? Particularly the exhaust valve since you got fuel all the way to the muffler.
My first WAG was piston . I guess I assumed the worst.Hopefully it will be something minor ...but I did spin it a good bit before squirting fresh gas into it. This mower has been notorious for taking awhile to start. It really needs a primer bulb like found on boats. I'll pop the valve cover off this evening and post back.