Carby float valve problem?

[mr blackstock]

Hello all,

I am continuing to battle fuel leaks in the carb bank, I have just replaced all the "O" rings, but have discovered in the no. 4 carby fuel coming up the needle and flowing straight into the cylinder, a fair amount too. 

I am assuming this means the float valve is too worn to stop the fuel?  Fuel is also coming out both overflow pipes on the same carby.

Float height is fine, needle level is fine, all other carbies are not gushing fuel.

Am I right in my assumption?  new float valve needed?

cheers, Gareth

[FJ111200]

Sounds like it mate.
I'd be tempted to put in a new valve seat aswell.

[andyb]

Toss the float into a cup of gas and see if it's not a float anymore.  If you've got a sink, that'd explain sommat.

Float needle wear is usually pretty easily visible.  On the seat... dunno, I've never seen rubber wear into brass, but you'd think a chunk of crap stuck in there, or a deep gouge, would be quite visible.


Is the float just stuck down?  Assuming you've given a couple of whacks to see if it'll unstick itself, that's a very frequent problem.

[ninjamuder]

also, look at the float pin....if it is even slightly bent, it will cause drag on the float pivot, and can cause a carb to overflow

[racerrad8]

Gareth,
    I just rebuild a set of carbs last week for a guy having a similar problem. I have never seen this issue before so it was a new one on me as well.

The carb float bowl gaskets had broken down and migrated into the float area. The gasket material was rubbing on two of the floats and was causing enough drag that the float would not float to allow it to shut off fuel.

Make sure the gasket has not impeded into the float area and is dragging against the float(s).

Randy - RPM

[mr blackstock]

Thanks for the good replies,

The gaskets are in very good nick, but I am thinking that while I wait for some monney to buy some new float valves and seats, I will float the float in petrol, to be sure.

The float pins were all straight, I am thinking a bent one would have caught my attention.

Thanks for the tips!
cheers, Gareth

[Shaun]

Another trick I've used to see if a float it leaking is to dry out the float, put it in the freezer for a while until it is good and frozen. Take the float out and put it in a glass of water (room temp) and sink the float to the bottom. As the air in the float warms up it will produce a stream of of bubbles if there is a leak. Used this mainly on the old brass type floats in older car / truck carbs. Of course sometimes you could just give the float a shake and hear the gas in the float and then no need to sink your float...

[Mark Olson]

If all else fails , lightly sand(400 grit) the needle tip area where it is gonna contact the seat . kinda like lapping it in so it seals.

I know it sounds strange but it works on these pesky fj carbs.

[ninjamuder]

400 grit sounds a bit rough really......i have done it using 1000 grit tho...

also, i usually chuck a q-tip in a cordless drill, and use a little mothers polish on it to polish up the needle seat....works great, just check your float level afterwards...just in case!!

[Mark Olson]

also, i usually chuck a q-tip in a cordless drill, and use a little mothers polish on it to polish up the needle seat....works great, just check your float level afterwards...just in case!!
[/quote]

that is a good idea as well