Topic: Carb help in Boston

[mkarcz]

Hey,

I am having a seriously frustratingly difficult time getting one of my carbs to quit pissing gas out.  Gas is getting really expensive now.  The float looks like it is at the right height, moving cleanly. and they are fairly clean.   It is weird because it will work fine for a few minutes and then as I rev it up it then starts to piss out, first a trickle then a stream than an intermitent spurt.  So if there is anyone that could shed some light on this problem, or anyone in the Boston area who could take a few minutes and help I would be very happy.
mark

[mkarcz]

Sorry, I have a '75 550k... And after posting I did more reading, sorry to repeat some things.  but if the o-ring on the main jet were shot, would that cause the bike to piss out gas, what are the different things that could do this?
thanks again
mark

[Cvillechopper]

It is weird because it will work fine for a few minutes and then as I rev it up it then starts to piss out, first a trickle then a stream than an intermitent spurt.

Where is the gas exiting?

[mkarcz]

gas is exiting out the overflow tube.

mark

[TwoTired]

Are all the carbs leaking or just one or two?

Each float bowl has a stand pipe.
 Check them carefully for cracks.  Use a small mirror if you have to.
Engine vibration can open them and cause faster leakage.

Or, lower the fuel level in the carb.

There are o rings on the float valve seat that could leak.

Or, the float valves/seats can be worn.

Have you checked for fuek contamination that may block the float valve from fully closing?

[mkarcz]

Only the carb that is second from the left, although the 3rd from the left was leaking a little, but, I adjusted it and it seems to be fine now.

I am not near the bike, but I will check the stand pipe.

What are the adverse effects of lowering the fuel level, and how big of incriments should I go by...I guess one mm?

Is the "float valve seat" the piece that pushes against the tang of the floats?

I sprayed tons of Carb cleaner throughout this carb and I haven't found anything blocked or really dirty.

Hope this helps in analyzing the problem.
mark

[TwoTired]

If it turns out not to be a cracked stand pipe, then lowering the fuel level (increasing the float height) ought to make some difference.  I'd just go .5 mm and check for effect.

Lowering the fuel level slightly leans the mixture.

The float valve seat is brass and is held in the carb body by a screw and clip.  The seat is what the valve fits into.  And, the valve is actuated by the float tang.

Some carb cleaners will attack the rubber of o rings and dissolve them.  If you used one of these types, the seat orings and the main jet o rings are probably damaged.

[andy750]

Hey Mark,
I probably have a single carb rebuild kit (for a 750 though -may fit? I have a CB750K4) or some basic spares in my garage in Roslindale (near JP) if desperately needed. Let me know if I can help. I have some basic experience with cabs.
Anyway if you want to meet in any case let me know (there are a few of us!)
Andy

[dusterdude]

mark,definetly check the stand pipe for cracks.3 of the 4 on my bike are cracked.i jb welded mine,they still leak a bit.i just put hose on em and ran them above the carbs,seems to work pretty good.now for that,does anyone have any good bowls for a k1 they want to get rid of.