I struck gas

[headcase]

Last fall, I put the bike in the shed, popped the battery out, and for various reasons there it sat...gas in tank, bags etc still on. Not the usual procedure for putting it away, I know. So...I start the yearly spring prep tonight and drained the oil. It was basically gasoline with an oily chaser. I had problems last year with one carb leaking fuel out the vent opening, out the air horn, and soaking the filter to the point it was so saturated the stuff ran down the side and onto the ground. The petcocks were recently replaced with full manual versions, so I had to shut them off every time I parked. I did go through the carbs last year, but they (one?) still leaks. How did all that gasoline get into the crankcase instead of out the carb?
Also, has anyone else done the petcock change and had issues with flooding like that? There's no vacuum diaphragm to hold the valve shut, I'm thinking a full tank might just feed itself past the needle and seat just from gravity alone....maybe? What say ye, O Gurus?

[grizld1]

Your last guess is correct. The float valve (needle and seat assembly) is a metering device, not a positive shutoff. When the float valve passes fuel due to defect or misuse, much of the overflow is going to find its way into the venturi, then into the intake port, then down the valve stem, then into the head, then into the cylinder, then past the rings, and from there into the crankcase. This is not an unusual occurrence; it's why petcocks are there to begin with. One or both of your petcocks failed to shut off the fuel flow.

[headcase]

Thanks Griz. What semi-baffles me is that when it's sitting at work, it'll leak out towards the filter through the vent hole, not into the motor (that I can tell). When started it'll pop n fart rich a few seconds until the filter cleans out, then all is well. I'll assume it was probably leaking in both directions...maybe? There's no other way for it to load the crankcase enough to dilute the oil so bad. Now I'm wondering how thin the stuff was towards the end of last summer. Would make for quite the experience if it backfired just right...

[grizld1]

Yep, that's what happens, fuel moves both ways; don't waste time trying to logic it out, just fix it. Now a word to the wise--don't assume that float valves are good just because they're new, especially if you installed cheap repops rather than real Mikuni brass. Bench test them and make sure. Hope you didn't run the motor very much with the crankcase full of fuel.