What is this nipple?

[jakubman1]

What is this nipple called and what could be some reasons iam leaking from it?? There is also another nipple on the top i think i "could" be leaking at. What are they called. Thank you
I know one is an overflow

Replaced fuel Petcock. Soaked carb then cleaned with carb cleaner then blew it out with compressed air.
I also replaced my valve needle AND polished the seat till it was nice and shiny.

[kuromi]

In the top picture, I think what you've circled is the overflow for the float chamber.
I'm guessing it's pointing down and the alloy shape in the bottom right is the float bowl.

If your float needle gets stuck open or doesn't seal correctly, excess fuel will drain out of here to stop it flowing up the carb and in to the engine.

I stuck a piece of fuel pipe on mine so if it does overflow it goes straight to the ground without dripping on the tranny case.

Not sure on the lower picture, Melody carbs are different.

[Meatball]

Mine had a mystery leak as well. I couldn't figure out where it was coming from since everything was covered in fuel after a ride. I replaced the valve needle and a new bowl gasket with OEM parts straight from Honda and it hasn't leaked since. The top pic is the bowl overflow. It will spew out fuel if your bowl fills up faster than your main jet can suck. The float is supposed to stop fuel delivery before that happens. Im thinking of trying a bigger main jet.

[vintagegarage]

I believe the top nipple is the air vent nipple. If I am correct, it's function is to keep the air above the fuel in the bowl at atmospheric pressure. Without a vent, as fuel runs into the carb by gravity some fuel would be forced up the main jet and into the air stream coming through the venturi into the engine. With the vent, as fuel runs into the carb, air is released through the vent, to keep pressure from building up inside the carb. Fuel is supposed to be sucked up the main jet by Bernoulli's principle, not forced up the main jet by fuel coming into the float bowl:

https://en.wikipedia.org/wiki/Bernoulli%27s_principle

[jakubman1]

So I need.a.new.bowl.gasket ?

[vintagegarage]

no.. the bowl gasket is a rubber O-ring shaped to fit the groove that runs around the joint between the bowl and the carb body. It rarely goes bad, and the float bowl is never supposed to get full enough to bring the gasket into play anyway. If fuel is coming out of either nipple, your float valve is not seating properly, and fuel is getting too high in the float bowl.

[jakubman1]

My float.valve. needle should only be held up by the float plastic right? No metal tab.
Do I need more polishing.then ?
I test by blowing.into gas.inlet.nipple?

[vintagegarage]

Yes, the plastic tab is all that pulls up the needle when the fuel level falls and that allows fuel to flow past the needle into the bowl. More correctly, it just lets the needle fall down or may slightly pull it down (when the carb is held upright.)

More polishing of the seat, likely, or a new needle with a fresh rubber tip, or both, assuming that your float has no holes in it, and there is no fuel in the float itself.

Yes, with the bowl removed, and the float in its lowest position you should be able to blow into the gas inlet nipple. When you raise the float with your finger, you should sense that the valve is closing, and when the needle valve is fully closed, you shouldn't be able to blow through the nipple. It should also take very light finger pressure on the float to close the valve. If you have to lift up the float fairly hard to close the valve, that is no good.

[jakubman1]

Hey thank you very much.
Im going to check that out later on.
Is gritty toothpaste good enough or should i look for some other compound?
Can i test the float in water? Or do i HAVE to use gas to see if it floats or sinks?

[vintagegarage]

If your float leaks, it will already have gasoline it in. You can just hold it up the light and see if there is any in there. Very rare to find a leaking float, IMHO.

I think a piece of tightly rolled up paper towel soaked in carb cleaner is enough to clean the seat. Anyone else care to jump in and comment?

[patthesoundguy]

If your float leaks, it will already have gasoline it in. You can just hold it up the light and see if there is any in there. Very rare to find a leaking float, IMHO.

I think a piece of tightly rolled up paper towel soaked in carb cleaner is enough to clean the seat. Anyone else care to jump in and comment?

Polish the seat with tooth paste or metal polish with a cotton swab in a drill. That should solve the leak problem if the float is fine.

[patthesoundguy]

My trick that I use to check the seat and float valve needle condition is to use a piece of fuel line on the carb and with the bowl off and float and valve installed hold the carb upright then turn it upside down while blowng light pressure on the fuel line. The weight of the float alone should hold a few psi at least. If the float has fuel in it, can repair it with a small drill bit and some super glue if you are desperate to get riding. Find the crack or hole first. Then drill two tiny holes in the float one on each side one up one down. Blow into the float like you are blowing a yolk out of an egg for Easter to get all of the junk out. Then glue up the holes and cause of the leak.

[jakubman1]

ha

I never used the drill on it. its a bran new float valve too

Thank you!

[patthesoundguy]

A new float helps rule that out buff that seat up and you should be good to go. I have a small 2 stroke generator that I got for $50 because the carb was gummed up so very badly from ethanol fuel being left to evaporate. The carb was just like a spree carb and the seat was a mess. The drill trick cleaned that seat like new. I even clean replaceable seats in small engine carbs because why pull the seat when it just needs a polish.

[jakubman1]

The drill did it! Dry as bones

Unfortunately I over tighten my carb manifold bolt. The one closer to the.motor.

Can I just get a longer bolt and put a nut on the end of it ? Like on wikispreedia
It seems a little snug. It's not wiggly at all.