Carb needle seat valves.. check this out...

[Shuriken]

I have a set of 79sf carbs. I've cleaned/inspected them.

Question is, when I tip them upside down, I cannot force any air through the fuel intake pipes. When I turn them right side up and feed them fuel, 1 set of them leaks.

What should I check/do?

Ben

[Ken Talbot]

If the needle and seat are in good shape but still leaking, it could be that the float is bad. If you submerge a cracked or otherwise leaking float in some hot water, the heat will cause the air inside the float to expand and you will see a stream of air bubbles. Even before you do that, listen closely as you shake a float to see if there is any fluid inside of it. A 'waterlogged' float won't float.....

[Shuriken]

The floats passed the test.... now what?

Ben

[xssiveone]

There should be a fiber washer between the seat and the body of the carb. Is it still in good shape?

[Shuriken]

Looks like they are in good shape...

Maybe I should just get the rebuild kits. ??

[Shuriken]

I think I will leave the float bowls off and connect the fuel line from the petcock to the leaky carb set. I will then observe (fuel waste) where the leakage is coming from.

Ben

[Shuriken]

I learn something new each time I clean a new set of carbs...

I tried everything and still, #1 and #2 carbs spewed fuel. They would not shut off for anything. I inspected everything closely multiple times and couldn't find any binding or gunk in the needle seat.

I was wondering what else could possibly go wrong. I then decided to force air into the upper tubes (bowl vents to airbox). To my surprise I discovered that the tube for carbs 1 and 2 was plugged.

After I figured that out and cleaned it so I could get air through it the carbs stopped leaking.

Hmmm.....

One for the archives, I guess.

Ben

[RS Thornton]

I had a similar problem on 1 carb for a 78E and it drove me nuts. What had happened was the other tab on the float was bent to far over, this lets the float drop way down. Then the float would stick an not come up and close. I bent the other tab to that the float could not drop down as far and now it works fine.
Scott