Crankcase filled with fuel

[Nomad]

Hi there, I've been off the forums for a while, but it's time to get the bike ready for the summer again.  1996 m900 with 41 FCR's.

I have replaced my petcock with a manual valve, as my vacuum pump failed years ago and my crankcase filled with fuel.

I noticed (unfortunately after letting the bike idle for 15 minutes) that my crankcase was once again filled with fuel while trying to summerize the bike.  I didn't do a proper winter storage, and it sat with low grade fuel in it all winter.

I drained the crankcase, put in a new fuel filter, and completed an oil change, and filled the tank with some non ethanol fuel.  I left the bike overnight and came out this morning to find a huge puddle of fuel beneath the bike.

It's hard to tell exactly where it's coming from, obviously the carbs, but it's wet around the fuel line itself too and appears as though it might be leaking from the case.  The crankcase is once again filled with fuel.

I don't know anything about my FCR's other than just what I did to install them.  I'm going to pull them off and clean them, I'll muddle my way through it I guess, I can't find a cleaning guide.

Is there anything else I should be looking for?

Thank you!

[Nomad]

Update:
Forgot to mention, when I checked on it this morning, fuel had also drained everywhere below the bike.

I got the carbs off finally, one of the cylinders and carbs was indeed filled with fuel. I pulled the covers to the floats, but it looks perfectly clean in there.

[ducpainter]

It doesn't take a very large piece of dirt to keep a float valve from closing. It could also be the float sticking on the shaft keeping it open. Clean everything and see what happens.

[Nomad]

Thanks DP.

I took everything apart, cleaned it, and put it back together. Now I can't get the bike to start. It chugs once then stops abruptly.  Charging the battery and checking connections since I tore a bunch of stuff apart, but so far no joy.

Edit: checked everything, it looks good. It was firing up great before I took things apart, despite the crankcase being filled with gas. Any ideas on what I might have missed? It just acts like it's trying to start once then stops immediately.

[koko64]

The carb on the flooded cylinder is the one to focus on. You can flush it and "wash" the face of the needle valve by removing the bottom float bowl cap (be gentle putting it back on) and opening the fuel tap with a can under it. The fuel flows over the face of the needle valve hopefully washing the wax, crud, dirt off it.
On the go you turn your tap off at speed and back on reseating the needle valves with fuel pump pressure.
Tapping the float bowls with a screwdriver at idle sometimes stops minor flooding.
Sometimes there's no way out of a carb strip and clean (usually with ethanol gelled up in it).

Modern fuels can easily do plugs in with flooding. If you haven't changed the plugs, consider it.
The fuel tap should be off each night. Sometimes crap from the tank innards is working its way through the system.

The float bowl needle valve is a glorified toilet cistern valve. That's a bit unfair, but gives a good idea what's going on in there. I have worked on at least five carburettor bikes of different makes with the same problem this year. Modern fuels are loaded with stuff that cleans injectors at 45 psi but clags up carbs at 3 psi. Add ethanol and it only gets worse. You may have issues whenever you leave your tap on overnight. Probably twice a year I'm riding along and have to turn the tap off and on again for 10-20 seconds.

Let us know how you go.

[Nomad]

Thanks Koko, hopefully the carb problem is solved. I took them off, took them apart and cleaned them.  The bike was firing up find until that point.  Now it just just doing the one chug and stopping. I can't get it going again to see if that problem is solved. But, at least I've got the petcock close while it's sitting there now...

[koko64]

Better change the plugs then.

[Nomad]

Store wont have any until tomorrow, will give that a shot then

[ducpainter]

You might try dripping a little fuel into the intakes until the pump can fill the float bowls.

[Nomad]

I think the cylinder/plugs just needed to dry overnight. It fired right up today, but I shut it down because of the fuel in the case issue. Now I'm replacing plugs and doing an oil change. Leaving the plugs pulled and rotating the tire while in gear to help it drain, hopefully that will be good. I don't want to warm it up or dump another 40 bucks worth of oil down the crapper.

[Speeddog]

If it was filling the crankcase while the manual petcock was turned off, I'd be checking that.

[Nomad]

Not while it was turned off. I had never had a problem before so i had just left it on all the time

[Speeddog]

It taught you a lesson, then! 

Make sure to at least dump the oil filter out, ideally just replace it.

[Nomad]

Yeah, 8'ish quarts of oil, 2 filters, and 2 new spark plugs later, things seem to be working well now. I haven't gotten to riding it yet, but hopefully those are the last of the surprises.

Thanks for the help!