'81 XS400 bike died, motor filled with gas, now what?

A little background:

I've had this bike for a little over a year, bought it running on one cylinder and replaced a carb with a broken float tower(?). While I had the carbs torn apart, I rejetted and cleaned to the best of my abilities.

That was about a year ago and I have been riding the bike ever since. I regularly ride canyons out here in Utah with the occasional 20 minute highway cruise to work. Its always ran pretty well but a couple weeks ago it started running poorly. Its always leaked a little bit of gas around the front sprocket(?).

I haven't been riding much because we're currently in the process of moving and work has been crazy. The bike has been sitting without being regularly ridden for the last month. Maybe 2 or 3 times in the last month or month and a half.

Jump to a few days ago:

Mid move, I went to ride the bike to a friend's house where I will be storing it. It started up fine and I put it into 1st, I got into 2nd, maybe 3rd and the bike just died in the middle of our neighborhood. I hit the electric start button and it sound normal, a little more gritty, not as smooth.

Today I pulled the carbs, looked at the floats, everything is looking normal. Petcock seems to be holding the gas just fine.

This is my guess:

I think as the bike sat, gas must've leaked down into the cylinders and thinned the oil. My leak had gotten pretty significant due to the thin oil and I shouldn't have tried riding it but I was only going 4 blocks no faster than 30mph so I risked it.

I started it up and then 1 block later, boom, failure. I drained the oil today and there must've been a full motor's worth of gas in there mixed with the oil. I drained it, flushed it a couple times and went to try to get it to turn over with starter fluid and no gas. I didn't want to hook up the tank and refill the motor with gas.

It's never blown fuses but it blew a couple and I couldn't get the lights or anything to work. I don't know if this is related to the gas in the tank but its a new problem. I couldn't get the bike to turn over but the crank turns freely with the kickstart. It still feels a little gritty but it was better than before. That's where it stands as of today.

I'm relatively new to motorcycles but I'm pretty confident with motors, tools and bolts. I'm hoping I don't have to tear the heads off and the pull the cylinders/replace piston rings. I'd probably consider paying someone to do that if it's not crazy expensive but we'll see.

What do you guys think? Where do I look next? Could this be a quick fix or a major problem.

 

BC, I just meant it was an abrupt failure when I said "boom".

The float tower was never repaired, I replaced that whole carb so I don't think the floats are the issue. Is there any reason gas would leak into the cylinders with a good petcock and good carbs?

Thanks for all the information, that should give me somewhere to start. I'm going to work on the electrical issues and then see if I can get the bike running.

Off note, did you ever surf any Jeep forums? The username sounds familiar.