Unknown mystery hole on BF8A carburetor?

Guys, can anyone tell me what the hole is on the top of the carb for my 1997 BF8A Honda? I recently bought this engine and it was "non-working". I have gotten it to run, but after taking apart the carb and servicing it, I cannot for the life of me deduce what this hole is for and can find no hoses or threads to indicate what would attach or go inside. The engine runs, but gas spits out from this hole! I'm new to marine engines, please help!

Re: Unknown mystery hole on BF8A carburetor?

Paladin27 said:

Guys, can anyone tell me what the hole is on the top of the carb for my 1997 BF8A Honda? I recently bought this engine and it was "non-working". I have gotten it to run, but after taking apart the carb and servicing it, I cannot for the life of me deduce what this hole is for and can find no hoses or threads to indicate what would attach or go inside. The engine runs, but gas spits out from this hole! I'm new to marine engines, please help!

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My guess is that it is a fuel bowl vent hole and if gas is spitting out the hole than you would need to check the float valve for proper closing. Hopefully someone with more specific knowledge can confirm this..................Don

Re: Unknown mystery hole on BF8A carburetor?

Don, after some further investigation, I think you are exactly correct. The float appears to have full travel, but something may be clogging the float valve. It looks clean visually, but am going to investigate further. Thanks for the incite and prompt reply!

dtj said:

My guess is that it is a fuel bowl vent hole and if gas is spitting out the hole than you would need to check the float valve for proper closing. Hopefully someone with more specific knowledge can confirm this..................Don

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Re: Unknown mystery hole on BF8A carburetor?

I have the same motor and just cleaned my carb, as it was stalling when put in gear at the end of the summer; appears low speed pilot jet was clogged.

I have no real idea, as following where these holes go is almost impossible. Gas does not spit out of mine. If you are willing to remove it again, try an air jet and see if you can figure out where the other end is.

Float valve hypothesis seems correct - if it doesn't close fully, the pump would be pushing fuel into the bowl, and it'd have to go somewhere. There's the hose exiting the bottom of the carb bowl, but as near as I can tell, that is only for exhausting the bowl when you open the drain screw visible in your pics.

As you can see, I'm no mechanic.

Re: Unknown mystery hole on BF8A carburetor?

Very likely that is the bowl vent, but I don't know for sure. Would make sense if your bowl float valve isn't fully closing, as the fuel pump will keep pumping more fuel into the bowl and out the vent (and partially into the venturi through the jets, but those are much smaller holes).

Next time you have the carb out, try the blow test. With the carb right side up, blow air into the fuel inlet (use your mouth/lungs for this, not compressed air). You should be able to do this easily. Next flip the carb upside down and blow air into the fuel inlet again. You should not be able to blow any air at all into the carb. If you can blow air in while it's upside down, that means that your float valve is not closing properly. That can be caused by a dirty/bad needle and seat. Or the float may either be bad or not moving smoothly.

Hope this helps.

Re: Unknown mystery hole on BF8A carburetor?

That hole is indeed the fuel bowl vent. The fuel you see is the float bowl over filling. Try priming the motor like you normally do, then un-plug the the fuel line. Pull the rope until motor starts. Let the motor run until it starts to run out of fuel, them plug the fuel line back in. It might take a few attempts, put hopefully will clear the the debris on the needle seat.

Re: Unknown mystery hole on BF8A carburetor?

Just an update that you guys are correct, it was the fuel vent spitting fuel due to the bowl being over filled. The needle vale is now cleaned out and the float appears to be working correctly, the carb is no longer spitting fuel out when running!