leaking float bowl

1977 CB 750

When the petcock is in the on position, one of the carbs streams gas from the float bowl drain (the rubber hose specifically). I pulled the float bowl down, and everything looks normal to me.  Is it possible that the float bowl just failed?  There's one for sale on ebay right now, but if there is something else going on, I will just take it to the mechanic.

[shultz_1978]

Just for starts. I would check the float valve to see if it is seating right. You can also hold your float bowl level fill it with fuel and see if the over flow tube is leaking.

[Piute]

     Don't understand how bowl could fail unless cracked ,check O-ring gasket ,ya-no it should be float adjustment or bad floats(they don't float).

[Lucky 1]

I doubt it is the float bowl but there is one thing that can happen.
Look with a magnifying glass at the brass overflow tube in the float bowl you may see a vertical
hairline crack. If so just clean it with sand paper or steel wool and solder the crack.

But the most likely culprit is the float valve.

When the float bowl is off, turn on the gas for a second with a rag in your hand or metal cup and when the gas starts to flow, gently lift up the float. The gas should stop completely.
IF it does not stop draining gas then you need to replace the float needle and also check the adjustment by the book.

You may just need to remove the float  and float pin and let gas drain out to clean out the float needle.

Float needles get worn from vibration and can start leaking. They need to be replaced every couple of years.
There are all metal float needles and there are rubber tip float needles.
If it is metal needle then you need to replace the needle and the seat.
If it is rubber, just replace the needle.

[cdaiscool]

You said its coming out of the hose. Is the screw in good condition? Use brasso to clean out the hole the screw goes into, make sure the screw plug is not corroded, and is tight.

Not sure how gas is leaking past that...

All good advice...I don't know enough to mess with the float needles, but at least we have a place for a mechanic to start...thanks...

[shultz_1978]

If you had the bowl off you were half way here. Learning and knowing how to work on your bike makes the ride that much better.

But if you don't think you can work on it that is cool to. You will fined a over load of info out of a great  bunch of people right here.

[Lucky 1]

They will probably charge him $400.00+ at the shop.

[shultz_1978]

Lucky would that be the first or the second trip to get it fixed. LOL just joking

[Piute]

[e-mail] wrote

All good advice...I don't know enough to mess with the float needles, but at least we have a place for a mechanic to start...thanks...

      Don't mess with the float needle just touch it ,is all your doing to see if it works/working,
    THEN YOU tell the mechanic what it is ,Ya have to show that you no or your going to be paying that 400 bucks .

I have no problem looking at it...it's just knowing what I am looking at and what to do is the problem...i will take a closer look at, but i don't know how it is supposed to function...once someone shows me something i never forget, but no one i know has the technical knowledge to really help

[shultz_1978]

Could you tell what carb the fuel is coming from. If need be I could snap some pictures of the  in side of a carb and show you what is what. Simply put if you know where the float is and how it works with the needle you can test it to make sure it is stopping the fuel.

If you need help you will get all the info you would want from some one one the form. Check out my post http://honda-cb750-s.456789.n3.nabble.com/1978-cb750-carb-swap-td3911046.html I was going to try swapping to newer carbs but thanks to some help from the guys here. I got another set of carbs and with some tools in hand tore them a part. I have got pretty good at taking them off and on.LOL But in the end it is nice when people know you did it your self.

Why give your hard earned money away for some thing you could do. It just take time.

I am all about taking the cheaper way out...the leak is coming carb number 1

[shultz_1978]

Save money   I think you are going to try this with the carbs on the bike. Get some rags or cut a old milk jug to put under the carb. This should be your carb. Check to make sure your over flow bleed off screw on the bottom of the bowl is seating right.  You know how to get the bowl off, With the bowl off you can see the over flow tube in the center. .You can check this out by holding your bowl level and putting some fuel in it. If that is good. Move to the carb and float, You should be seing this  If the carbs are on the bike, Push up on the float ( not to hard just easy ). Hold it and turn on the fuel. If it leaks shut the fuel off. Remove the keeper pin with a nail or small screw driver Be careful not to lose any part. Once the pin starts coming out hold your float so you don't drop any thing ( float and needle )  Once out you can check your needle and float.  You can use a good q-tip to clean out the needle seat hole. Hope this helps you out. And this is what you are looking for.

But you may have round top carb and they are different.

So i took the float bowl off, ran fuel through it multiple times, pushed the float up and down, noticed a bunch of gunk in the bottom of the yogurt cup i was using to catch fuel

Then i compared it to another carb which the needle functioned correctly

So i went back the bad carb, ran mor fuel through it, pushed the float up and down until no junk came out, the float started to work correctly, i put the bowl back on, turned the fuel on,  and the leak stopped

Looked like there was some junk stuck in the hole where the needle goes...problem solved for now

Is there any PM for this to prevent this problem?

Your post is perfect for the next time this happens

[cdaiscool]

Inline filter. Catches the junk that goes from gas tank to carbs.

Get some fuel line that is the same size as yours currently (a couple feet) and a carburetor inline fuel filter from the store. Personally, I only run the plastic molded ones that Autozone sells; the ones with the changeable filters also have removable ends. Nothing says "crap" like a warm fire on top of your carbs if they start leaking.

Anyways, just find a nice way to run the line from your petcock, to filter, to the inlet on the carbs. And that's it. 4 hose clamps, some hose, and you're home free.

[alehman]

Definitely run an inline fuel filter on your fuel line.