Carburetor questions

[rev_mook]

Hey gang, I have a couple elementary questions about Bing carburetors.  Some background first; I've been traveling around putting lots of miles in and made a stop at my parents place in South Florida.  I parked the machine for a few days and shut off the fuel supply.  One morning when I had a few spare hours I decided to check valve clearances.  Once the spark plugs were removed I rotated the engine with the rear wheel to get TDC.  Fuel shot out of the left side spark plug hole all over the floor.  Great. The whole left side cylinder is full of gas.  I'm really glad I didn't try to start the engine or I could have probably really caused some damage by hydro-locking it.  When I tore into the carburetor I found my fuel shutoff valve doesn't fully shut off the supply.  This makes me think the float got stuck somehow, as the float needle appears to be operating correctly, or perhaps some debris got stuck in the float needle seat and failed to stop flow?

So, I have some simple questions.

1- Are the floats hollow?  I'm wondering if they can take on fuel and sink.
2- Where is the float bowl overflow hole?  Mine seems to be excessively clogged.  I've had a sticky float needle before in this bike and the excess fuel ended up in the ground, not in the cylinder.  I need that hole to work from now on.
3- I think gas got past the rings and into the oil.  I'm going to replace it just to make sure.  Would you recommend replacing the filter as well?  I have about 3K miles on the oil/ filter.  I have not run the machine in this condition.
4- I think I'm going to order a new float and float needle.  Are there any other parts I should order?  I'm going to second-day air the parts because there are too many mosquitoes here and I want to go home.  I don't want to make two orders.

After taking the carb apart and inspecting the float, float needle and jet o-rings and finding no visible problems I put the carb back on the machine with just the elbow joint, omitting the rubber piece that joins the carb to the engine head.  The idea was to wait and see if the garage floor would be flooded with gas in a few hours.  So far, things seem normal and I'm unable to reproduce a condition which would fill a cylinder with gas. :-/

Any other ideas?
~Mook

[Bob_Roller]

By chance, did you park the bike on the side stand ?

The floats are made of a foam material and they do on occasion absorb fuel, alcohol in the fuel seems to aggravate the problem .

[nhmaf]

How much gas came out?   There isn't a huge amount in the fuel line, so perhaps your fuel petcock isn't actually turning off?

Yes, the floats can become heavy and sink.   The black, separate float kits available from Bing do require a modded or new float bowl - I personally do not think that they are worth the effort/$$ and would recommend simply getting new floats of the "normal" variety (which go on a common "arm" or beam to close the valve.

Sometimes nothing is really wrong but the arm become slightly torqued to one side (as in sitting on the sidestand) and a slight amount of surface roughness or accumulation of sticky stuff prevents the floats from fully rising and closing off the float needle/valve.  Or, a  bit of rust or dirt or chunk of rubber from the inside of the fuel line comes loose (as can happen with the ethanol in the fuel these days, especially if the fuel is left sitting for long time).  These small foreign particles can lodge in the float valve or block the seat so again, the needle isn't fully closing off the fuel flow.   Again, if the gas was more than what the inside of the fuel hose would hold, then it is possible the petcock may need attention.    

[montmil]

If you do order the floats and associated bits, remember to get a couple of the tiny, wire "clips" that secure the float's tab to the float needle.

If you park the bike on the sidestand and leave the petcock turned on... Uh Oh! Possibility that fuel could pass into the carb, leach past the rings and enter the oil sump.

I'd change the filter for simple peace of mind. And perhaps rebuild the petcock.

[Barry]

1- Are the floats hollow?I'm wondering if they can take on fuel and sink.

They have been known to absorb fuel but not usually to the extent that it causes flooding of the cylinder. More likely to be debris in the float valve.

2- Where is the float bowl overflow hole?Mine seems to be excessively clogged.I've had a sticky float needle before in this bike and the excess fuel ended up in the ground, not in the cylinder.I need that hole to work from now on.

There is a brass overflow tube in the float bowl with the outlet underneath the bowl.  Usually it works fine but it's a very small bore tube so even if clear it might not have the capacity to match a seriously leaking float valve.

3- I think gas got past the rings and into the oil.I'm going to replace it just to make sure.Would you recommend replacing the filter as well?I have about 3K miles on the oil/ filter.I have not run the machine in this condition.

If you think there is enough fuel in the sump ( dipstick level ? ) to require an oil change and the engine had been run I would definitely have changed the filter. As it hasn't been run other than a few slow turns to set the valves the fuel shouldn't have reached the filter and I would expect it's OK.  Never tried it but as the specific gravity of fuel is a fair bit lower than oil it might just sit on the surface if it was added slowly and not mixed up.

4- I think I'm going to order a new float and float needle.Are there any other parts I should order?I'm going to second-day air the parts because there are too many mosquitoes here and I want to go home.I don't want to make two orders.

Most of us have probably had an isolated instance of fuel over flow. I've had it happen once in 6 years.  If the floats and valve look OK there is no reason to suppose it will be an ongoing problem.

[tvrla]

If you're getting new floats, get the black alcohol resistant ones. I don't even know why they'd still offer the white foam style now that the black ones are available.

Check to make sure your petcock is cutting off fuel flow.