Topic: Carb. Leaking ?

[rddcw]

Just recently purchased a 75' CB750 K5. I did notice that the Right outside Carb. is leaking from the overflow tube when the motorcycle is not running and the fuel petcock is off. It drips more when the bike is on the center stand.

Pulled carb. bowl off. Float is free and raises/lowers fine. Pulled the float seat off after removing float. Seat and needle look good but cleaned both to make sure. Changed the gasket too. Inspected float-no cracks. Overflow tube in carb. bowl is good too. When the float assembly was off as well as the seat and needle, gas was steadily dripping from carb. seat opening?

Re-installed float assembly but still dripping. Only when I physically raise the float does the drip stop. Re-assembled carb. Thought I had it for the bike didn't have any gas coming out of overflow tube, but "intermittently" it still leaks?

Do you Tech. Guys have any ideas?

[eigenvector]

The fuel line has gas in it, you didn't say how much or how long it dripped - but it's possible that it's just whatever gas is in the fuel line.

[links56]

Does the little pin on the end of the needle still have spring to it? you should be able to push the float lightly and it should spring back to a point.

[rddcw]

Eigenvector, that might be it but it's only 1 carb. that drips. And yes it is intermittently. Kind of like it burps out a little gas then stops. Gas puddle when it does happen is probably about a half of bowl in volume?

And link56, the needle has plenty of spring to it.

[eigenvector]

All I was really getting at was that the petcock is functioning normally, that it's not pouring out - indicating a major leak.  I would fully expect it to be one carb only.  My guess based on what you just said is that your fuel valve is on it's way out.

Is the fuel level too high in one of the carbs perhaps?  Fuel might be just barely below the level of the overflow - that valve isn't perfect, a little bit will drizzle in from time to time.

[rddcw]

Rob,  I'm assuming when you say Fuel Valve, your referring to the Fuel Petcock?

[madmtnmotors]

Two issues:

>Fuel valve is not shutting off properly. There should be no fuel passing through the fuel valve when in the "off" position. Rebuild it with new seals.
>Either float height is wrong in the leaking carb or the float needle and seat need to be replaced (most likely). I would replace all float needles and seats at the same time.

[rddcw]

Thanks Wilbur,  I'll look into a Fuel Petcock rebuild kit as well as the float seat and needle kit. Any recommendations where to purchase these parts?

Also, Float height adjustment. I have a clear tube w/fitting that I used on my 77' KZ1000 to check the float height. I'm seeing on the Forum that that measurement needs to be 3mm under the float base gasket?

If not using clear tube, what Float measuring gauge would you recommend and at what height on the gauge?

[madmtnmotors]

Any recommendations where to purchase these parts?

I would recommend Honda parts for the float needles and seats. At $17 each they are a little pricey though, P/N 16011-375-004

4 into 1 has aftermarket at $5 each, but they can be a roll of the dice. For the price they might be worth a try? http://4into1.com/replica-keihin-2-0-float-needle-valve-assembly-16011-375-004/

The Honda parts will be manufactured to tighter tolerances and often provide the longest service life.

[links56]

Regardless of weather the fuel petcock is working properly or not. you should be able to leave it on without having it leak out the overflow. They are 2 separate issues. If the needle is springy can you leave the bowl off and hold the float up with the fuel turned on? fuel should not come out, if it does, the needle and seat need replaced. If it doesn't then the float level is probably too high.

when you take the fuel line directly off the petcock and it is shut off does fuel still come out of it? if so then the petcock needs rebuilt if not you were probably just seeing what fuel was already in the fuel line.

[rddcw]

Links56,  When I did remove the float bowl I was able to raise the float assembly up and fuel did Stop dripping. So with that in mind your probably right that the float level is too High.

I didn't get around to removing the fuel lines from the petcock to see if it leaks with it off yet but will.

I know how to adjust the float level by bending the tang but which way either up or down?  What method are you using to check the fuel level?

Are you using a float level gauge or the clear tube method?

[links56]

I just use a clear piece of hose. If the carbs have an overflow spigot I just hook it to that and open the bowl drain. Make sure the bike is level and you want it 3mm below the bowl gasket flange. you will want to bend the tang up toward the top of the carb so the float closes the needle earlier than before. Remember a little goes along way, you will probably barely tweak the tang. you can put the carbs in a vice, make sure they are level, and hook a funnel to the fuel line and set all this stuff so you don't have to take it on and off the bike. Check the level first to make sure it is high though.

[links56]

If you haven't seen this Flybox1 has posted an awesome picture which shows how it should be hooked up and what it should look like.

http://forums.sohc4.net/index.php/topic,149299.0.html