Topic: Carbs Leaking Fuel Heavy - Confirm Float Height Setup

[uncle_fester]

I have a '74 CB550 that I've spent a lot of time messing with, but not so much time riding. Each time I adjust anything in the carbs and re-install, I usually get some fuel overflow when filling them back up for the first time. Today, all four carbs were overflowing heavily out the drain tubes. I shook the bike around to see if the floats would settle, but no luck. I have it setup with the gas tank about 18" above the carbs with it set on "RES" and about 1.5 gallons in the tank.

Here is what I've done: Confirmed all floats are leak free. Sanded the float shaft so they all move freely and easily. Set the height so that the top of the float is 22mm above the bowl edge when the float tab barely touches the needle.

Is this the proper way to set the float height for this bike?

It should be noted that the needle and seat are reproduction from 4into1.

[flybox1]

if you shut off the fuel, do they stop leaking?
how about taking a rubber mallet, or a block of wood, and gently tapping on the carb mounting plate.
This usually un-sticks stuck floats.
If your float height is right, they should stop leaking.

If they continue, please clear tube test #1 and #4 to see what the actual fuel level is....

[bochnak]

Take it apart and pressure test the float needles:

[bochnak]

It should be noted that the needle and seat are reproduction from 4into1.

Have a link?

[flybox1]

It should be noted that the needle and seat are reproduction from 4into1.

Have a link?

http://4into1.com/replica-keihin-float-needle-valve-assembly-16011-329-004/

[bochnak]

It should be noted that the needle and seat are reproduction from 4into1.

Have a link?

http://4into1.com/replica-keihin-float-needle-valve-assembly-16011-329-004/

Yeah, that might be the problem right there. OEM costs $30, these are $5? Sometimes you get what you pay for.

[uncle_fester]

if you shut off the fuel, do they stop leaking?
how about taking a rubber mallet, or a block of wood, and gently tapping on the carb mounting plate.
This usually un-sticks stuck floats.
If your float height is right, they should stop leaking.

If they continue, please clear tube test #1 and #4 to see what the actual fuel level is....

They continue for a little while, but I think it's because they're over flowed so much.

I feel like I did a good job on sanding the shafts of the floats so that they easily move. Hard to imagine they're stuck. They're all doing it, and I've rocked the bike around to unstuck them. I'll try a mallet on them any how.

Are there any sources for a genuine needle and seat?

[flybox1]

They seal just fine, and have float valves the same length as OEM.  I used them on my 74 550K.  (Spendy at $20 for the set)
PO is getting overflow out of all 4 carbs.  One of these might be bad, but not all 4.
His problem lies elsewhere...

[flybox1]

They continue for a little while, but I think it's because they're over flowed so much.

I feel like I did a good job on sanding the shafts of the floats so that they easily move. Hard to imagine they're stuck. They're all doing it, and I've rocked the bike around to unstuck them. I'll try a mallet on them any how.

Are there any sources for a genuine needle and seat?

You'd be surprised at how easily they can hang up.
bang on the carb plate as you turn on your fuel, and if that doesnt get the floats to pop up and seal, clear tube test your fuel levels.
It'll only take a second.

The compressed air test is a good one

[uncle_fester]

I took the bowls off the carbs. I first reseated the float valve bodies and gently tapped them in with a plastic tool and small mallet. They are very secure. I then noticed the float heights were too high. I must have previously adjusted them from the other end and didn’t take in to account both sides of the float. Got them dialed in now. No more leaks!

[tlbranth]

You need to stop just trying stuff, build a holder for the set and bench test them. I personally don't like the clear tube test Flybox refers to but at least it's a bench test. I devised what I think is a better bench test which you can see here:
 http://forums.sohc4.net/index.php?topic=166447.0
With a bench setup you can really go to town and see what's up. For instance, take the bowl off a leaker and lift the float manually. Does it stop the flow? If yes, then the needle is OK. Shake the float. Any fuel in it?
Look for dimples on the float tang. They'll hang up the float and cause a leak. After a while they all get dimpled. Here's a repeatable fix I came up with:
http://forums.sohc4.net/index.php?topic=166564.0
Don't get discouraged. It's a marathon not a sprint. When I first restored my 750 I was getting serious burbling and getting 17mpg! Now it runs quite well (although #1 runs quite rich) and I get close to 50mpg.