82 cb650sc problems - wont stay running and gas in air filter box

[Rickk]

So I have an 82 Nighthawk 650 which ran fine up until today.  I left it outside and it was raining pretty hard, tried to start it today and it wouldnt stay running without giving it gas and/or the choke on.  I assumed I got water in my tank to I emptied the tank and the gas that was in the carbs and refilled with fresh fuel and tried to start it again and it still acted the same way.  

Also when I was looking at the bike I noticed gas dripping out of the air cleaner compartment, so I took the cover for it off and the air filter chamber was filled to the top with gas and it all came pouring out.  Now I have no idea how that happened, I'm not sure if thats also related to the rain or what.  I got all the gas out of there and plan on buying a new air filter, but I dont want to put it in until the problem is fixed.  

any help would be appreciated...thanks

[Brittles]

Stuck float in the carbs maybe.
Petcock not working properly maybe.

Check/smell your oil to make sure your crankcase isn't full of gas.

The hard rain really shouldn't affect your bike unless you've got things going on that your not telling us. 

[Rickk]

The only other thing I can think of is that I had just put the tank back on right before I noticed the gas dripping out of the air box.  I'm not sure how that would have done it though.

[Bumblebee]

Assuming it was shut down, the fuel had to get past two valves:

A stuck float would let fuel into the carburetor venturi which can flow back unrestricted into the intake boot box then on to the air box. (check the oil and cylinders while you're at it to avoid hydraulic locks) It's easy to remove the float chambers and unstick float valves or remove contamination though you have to pull the carburetors off the bike to do so.

The vacuum fuel shutoff isn't working or is bypassed. If the engine is off, no fuel should flow to the carburetor.

I'm not seeing rain doing this.

Has it been running properly up to this point?

[Rickk]

It ran fine up until this point.  I read that tapping the float bowls with something can loosen a stuck float, so I tried this by tapping them with a screwdriver handle.  I started the bike first try after that and it idled for maybe 10 seconds (everything sounded normal) and when I gave it a little gas it died.  It wouldnt start after that no matter what I tried (choke, no choke, throttle). 

However, no gas got in by the air cleaner that time while trying to start it.

I checked the oil and it seems to be overfull.  The oil light is also on, which is wasnt before while the bike was running properly.  The oil seems to have a very slight gas smell but I'm not sure, it could just be my hands since they had gas on them.

[Rickk]

I bought some new oil and plan on changing it tomorrow, hopefully that will help maybe.

[ariwhiteboy]

I would check the oil more thouroghly, might have gas in it, if so that's a bad sign.  Means gas is making it's way into the bottom of the crankcase...could cause big BOOM.    As far as a solution goes I'm leaning towards a problem with the floats.

[Rickk]

how do I know for sure if I have gas in my oil?  what should I do to solve that problem? 

[ariwhiteboy]

You can smell the oil with clean hands away from the bike, but if you have a fuel leak that may still taint the odor.  Best thing to do is drain the oil into some clean container, if there's gas in the oil it should float since gas is heavier than oil.

[Rickk]

So I started the bike today without choke and it idled ok, but it seems to be running rough still and sounds like its about to die the whole time.  I pulled one of the plugs (which are brand new maybe 60 miles ago) and the end of it was super black and wet, which I'm guessing was just from running it with the choke on so long before and having to give it so much gas.  Also there is some oil leaking from the crankcase (I think?).  And it starts smoking and I can smell it if the bike is running for a little while.  I circled the area in red where the smoke is coming from in the picture.

[Rickk]

keep in mind all of this happened out of nowhere one day when I tried to start the bike

[surfswab]

All the symptoms you describe point to a faulty petcock diaphragm.  The diaphragm's function is to keep fuel flowing so long as the motor is running and producing vacuum.  When you shut the motor down, the vacuum stops, causing the  diaphragm to  release a fuel valve that shuts off the flow of gas.  If it's malfunctioning, fuel will continue to flow (unless the petcock lever is turned to off), which will eventually fill the carb bowls and begin to overflow thru the overflow tubes AND into the intake manifolds, the airbox, the oil breather apparatus and the crankcase.

The fix:  Immediately turn the petcock of the "off" position.  Remove the tank, then the petcock.  Inspect the rubber diaphragm for splits, tears, pinholes, etc. It's a 99 percent certainty it's faulty.  It can be rebuilt with a kit from Bike Bandit (about $20).  Once that's done, drain the carb bowls, drain and change the contaminated oil, clean or replace your spark plugs, drain any residual raw fuel from the air box and crankcase breather.  If you have a paper air filter, change it or let it air dry.  Once all that's done, you should be good to go.

[noahnsteph]

If you haven't already you need to immediately drain the oil and replace the filter. We went for a ride today and my buddies XS1100 didn't want to start and when it did there was a huge plume of exhaust and oily gas started pouring out the air box.  We'd noticed that the one of the bowls was leaking the other day at bike night but thought we'd gotten it straightened out.  Guess we were wrong since the gas had filled up the air box ran back into the engine, past the cylinders and filled the crank case. We must have emptied out 8 quarts of oil/gas this morning when we changed the oil.  This same problem blew up the motor off the donor bike last year.