Topic: carb question

[Buffo]

As I have written in earlier post I have just overhauled my carbs on my 1978 CB750K8 and that it will not start. I am working on that but...

Do the screws that you use to sync the carbs need to be tight or are they suppose to be turned out at all? I screwed mine down tight. My kit came with new ones.

Is checking the float hight with a clear piece of tubing hooked up to the float bowl overflow/drain nipple and holding the tube up against the bowl, with the drain screw open to see how high the fuel level is a good way.  Did i explain that well enough?

Don

[Bob Wessner]

Yes, the screws for carb synching should be tight and there should be a washer under them. Some folks have established the fuel level in the bowls useing tubes as you describe, but just my personal opinion you should use the spec float height as directed and use the tubes perhaps to verify things.

[Buffo]

Thank you Mr. Wessner.

Don

[Gordon]

If your float bowl overflow tubes are in proper working order, you won't see any fuel in the clear tube hooked up to them.  The only way fuel will come out of them is if the float height is set too high or the float valve is stuck open.     

[Bob Wessner]

Good catch, I thought he was talking about subbing the drain screw for a tube.

[Buffo]

I was going to Put a clear tube on the drain nipple...hold it so the opening is above the float bowl a little..open the drain screw and let the fuel rise up in the clear tube. It will be the same level in the tube as the bowl.

If i could get the measurement of how far down the fuel should be from say the bowl gasket I could see if i was having a float problem without removing my carbs.

It would have to be done to eacn carb

don

[Bob Wessner]

Buffo,

Gordon is correct, the nipple you are referring to is the bottom end of a tube that entends up through and above the fuel level in the bowl. Nothing should come out of this unless the float valve is stuck or the float height is too high. If you had a spare bowl, you could break off the part of the tube inside the bowl, then your idea would work, but you would have to move it from bowl to bowl.

When you overhauled your carbs, did you check/set the float height with a gauge or small ruler? One possible method to verify your fuel height is to temporarily replace the drain screws with short lengths of plastic tubing, which is what, though misreading, is what I thought you meant originally.

Under similar circumstances, here's what I did. I went to the hardware store and got about a foot of plastic tubing each of a different diameter close to the diameter of the bowl drain screws. Sure enough, one was too thick, the other slightly too thin. However, by spiral wrapping some Teflon tape (used in plumbing to wrap pipe threads), I was able to build up the diameter of the thinner tubing and allow me to "screw" the ends into the float bowl drains. They worked well for the amount of time needed to check the levels. Any clear tubing will do. It won't be on there long enough to worry about its compatability with fuel. Below is a previous post of mine, more or less along the same lines.

http://www.sohc4.us/forums/index.php?topic=1757.0

[TwoTired]

I believe the newer model carbs may be different than the older models. The nipple at the bottom of the carb is indeed coupled to the stand pipe in the carb bowl for overflow.  However, the drain screw opens the bottom of the bowl into this tube.  I believe what Don originally proposed will work with checking fuel levels in the bowls.

I wish I could tell him what actual fuel level is correct.  But, I don't know.  I just go by factory specs for setting float levels.

Cheers,

[Buffo]

indeed... my float bowl overflow AND drain screw are BOTH  connected to one nipple on the bottom of the float bowl. Which is inturn connected to a rubber hose that goes uder my bike. Of course one for each carb. 

This is why I thought that my Idea would be a easier and much quicker way of checking for float hight since it could be done without removing the carbs.   Of course they would have to be removed for adjustment.

I am going to check/adjust my floats with the carbs off. Reinstall them on the bike  and fill them with fuel. Then I am going to remove one of the bowls, hopefully without losing any of the fuel in it. measure from the top of the bowl to the fuel.
This should give me the measurement I need to check my floats in the future with the method I described.

Don

[Bob Wessner]

Still struggling to envision this set-up, but certainly take your word for it since I'm not familiar with later carbs at all. Good luck.