Topic: Carbs Leaking from Float Bowl Gasket

[OCW85]

I recently cleaned my carbs on my cb400f and and put everything back in the correctl order. The float bowl gaskets were flattened and sticking to the channels so as carefully ad I could, I "peeled" out the old gaskets and cleaned the channels with a brass brush and small metal pick to get the pieces the were still sticking. I used the pick very sparingly and with as little force as possible.

I purchased new gaskets from 4into1 (pretty sure they aren't OEM) but they are in the "home base" shape on the bowl. That said, they were a hair small, so with some very minor stretching and some light grease to hold them in place, I installed the float bowls.

I reinstalled the carbs, turned on the gas, and BAM - all 4 start leaking from the BOWL GASKETS and NOT the overflow tubes. I took them back off, double checked the float height (21mm), cleaned the valve and valve seat, reinstalled them and got the same result.

I have not tried the clear tube test, but I did lightly hit the bowls in case of stuck floats, but that did not help.

On further eval, the o-ring around the brass valve seat looks pretty flat, which leads me to think gas is getting past the valve when cloased.

What I find odd is all 4 leak from the same spot and they are NOT leaking from the overflow tubes. When I first got the bike they leaked a bit from the tubes but not the bowl gaskets. Did I mess rhe gaskets up but stretching them a little? Also, what are the odds all 4 need the valve seat o-ring?

Any help would be GREATLY appreciated!

[jonda500]

Seems in retrospect that you should have bought new valve needle and seats instead of float bowl gaskets!

Your old float bowl gaskets weren't leaking but the new ones are so none comes out the over flow tubes (because they are higher than the top of the bowl!). Are the new 'home' o-rings protruding out of the slots a little before tightening the bowls on? if not I would email 4into1 and tell them your issue with them not working!

Check your needle valves closely - if you can see a ring even a faint circle in the surface then you'll need new ones (which will come with new o rings on the seats)
John

[flybox1]

The bowl edge is lower than the overflow valves.
If gas is getting up to the bowl o-ring seam, then the floats are not shutting off gas for one or multiple reasons:
Tank debris preventing float valve from sealing
notched float tang catching the float valve tip
notched float valve tip not sealing
float catching on a rough float post pin
float catching on a bowl o-ring sprung out of its channel
float hanging/stuck in the down position
incorrect float height setting

eliminate all of these, one at a time.

[Duanob]

Did you compare the new bowl gaskets with the old ones? maybe they are just too thin to seal properly? Are the old ones still in one piece? You can use them until you can find some OEM ones, especially if they sealed before.