carb gas leak - cracked body?

[rob650]

Good Morning,

Trying to chase down an intermittent float bowl/overflow condition,  and saw that fuel comes out from behind this black plastic plate (see pic, plate circled in red).  I'd always thought the plate was just cosmetic, and attached to the carb body like a badge on a car fender.  So, seeing fuel pour out from behind the plate makes me thing the body itself is cracked/damaged, and just happens to be behind this plate.

Can someone confirm this, or correct my bad guess?  And assuming the diagnosis is right, means the carb body is shot?

Thanks for any advice.  Have a good one

[Bob_Roller]

Only way to know for sure, is to remove the four rivets and see what you have behind the plastic badge .

Possibly could be a brass plug that is placed in a passageway that was drilled in the carb body has come loose .

I just went out to look at the left carb on my '81 R65, there is a hole at the backside of the plate at the lower right side, if I'm not mistaken, this is the vent for the float bowl .

If there is fuel coming out of this hole, the float bowl is overfilling with fuel .

The float needle valve is not shutting off fuel when it should .

Deformed rubber tip on the valve, debris caught on the sealing area, or possibly a heavy foam float that has absorbed fuel .

Barry beat me to it  , I had to go in the parking lot at work and look at the bike

[Barry]

If you look carefully close to the edge of the plate, there is an overflow bleed hole in the casting just to the lower right. Could that be what you are seeing as a leak from the plate.

Probably an issue with float levels or the float valve.

[rob650]

Thanks Bob and Barry, that puts my mind at ease that the carb body (probably) isnt borked up. 

Have been throwing new seals/o-rings/floats/needles,. etc... it still wants to randomly piss on my boot.  Fine. ill keep at it.  Thanks guys.

[Justin B.]

Sometimes the seat, that the float needle presses against, gets a bit rough and can cause intermittent incontinence issues.  I had one that was giving me fits, years ago, and the dealer in Austin told me to put a little fine valve grinding compound on the tip of a freshly sharpened pencil, remove needle, and using the pencil gently rotate it against the seat to clean it up.  Worked like a champ!

[Tony Smith]

Have been throwing new seals/o-rings/floats/needles,. etc... it still wants to randomly piss on my boot.  Fine. ill keep at it.  Thanks guys.

Are the original brass screens still in place on the fuel tap? if not, fit an inline filter in the fuel line to trap small things that might otherwise prevent the float needle from doing its thing.

The float needle and seat in a Bing is remarkably long lived and really pretty durable.

I'm assuming you have eliminated a "sunk float" as the cause.

If the screen is in place on your fuel tap then the next biggest suspect is the fuel line itself - have you disturbed it at all lately? Some types of "rubber" seem to go hard internally and if the hose is disturbed will release minute particles of hard rubber - tailor made to cause the float needle to not seat.

Next time it pisses on your boot - simply remove the float bowl, turn the fuel back on and "jiggle' the floats until whatever is blocking the needle clears and fuel flow ceases when you lift the floats.

[Tony Smith]

If you look carefully close to the edge of the plate, there is an overflow bleed hole in the casting just to the lower right. Could that be what you are seeing as a leak from the plate.

Probably an issue with float levels or the float valve.

To which I'd add that given how high up that vent/drain is, I'd be checking the overflow drain in the float bowl to make sure it isn't blocked