Carb float levels

[Neill C]

So I've now done a valve and seat swap as well as a light seat and float pin polish and the only way I could prevent it from overflowing was by ever so slightly lowering the float. It hasn't overflowed for over 24hrs now so I'm going to do a clear tube level check to see what the actual levels are. I reckon it'll end up being my inability to set the floats at the right height in the first place thats the problem! Thanks for all your advice.

[Nurse Julie]

This may be of help.
http://www.sohc.co.uk/index.php/topic,23233.0.html

[deltarider]

Neill, the clear tube method in practice is not as simple as often presented. Therefore I advise anyone to do this method first, to check if anything is wrong at all. Often there's nothing wrong, but there will be after people have 'adjusted' the floats. My test will not lie and is very simple. First check if your carbs are fed fuel the same way as mine, knowing: one tube feeds carb 1+2, the other 3+4.  http://forums.sohc4.net/index.php/topic,185754.msg2151647.html#msg2151647 But this method also applies when carbs are fed by one tube. If you understand the principle, you can perform it, be it with a minor variation ofcourse.
Know that all CB500/550s are very sensitive to have the fuellines in exactly the right dimensions and that extra inline filters are a no no.
If you've find one carb that is off and tapping the floatbowl with the stump end of a screwdriver didn't help, then it's time to remove that floatbowl for further inspection. Succes!
Oh, I cannot be of help with any aftermarket parts, as I have no experience with them.

[Neill C]

I readjusted the float levels and did a bench test
 No overflow for a couple of days. I refitted carbs and still no overflow. Then I went out for a 20 mile ride.  One carb overflowing like you wouldn't believe. I head home, park her up, turn the fuel on and no overflowing.  I want to cry!😭😭

[McCabe-Thiele (Ted)]

I feel your pain - was it the same needle & seat that you moved?

If it was  me I would be fitting a new float plus the needle & seat assuming the originals  or a decent new aftermarket replacements are available.

Just a long shot but is it fresh fuel i the tank?

[Sesman]

Hi, Neil.

It is of course possible that the fuel overflow was caused by some debris, now cleared? Stick with it.

[Neill C]

Yes. Fresh fuel. When it's not raining I'm going to let the bike sit for a few hours with the fuel on and then to go out for another ride to see of it overflows again. I just can't see what else it can be other than debris. If the float had a hole in it it would have carried on overflowing when I got home so it can't be that. Even if the level in that bowl is incorrect why would it overflow one minute and not the next. Onwards and upwards!

[deltarider]

What one interprets as the 'wrong float level', can have several causes.
Debris that prevents the valve to close is one. A floatneedle that sticks in the valve is another.
Correct working order:
1. Tap floatbowl with stump end of screwdriver. If that doesn't help >
2. Remove drainscrew and flush floatbowl by opening and closing the petcock. Collect gas ofcourse.
3. Combine 1. and 2.
If 1 or 2 (or combination) doesn't work, remove floatbowl for further inspection.
Consider 'readjusting the floattang' as the last, the very last option. I never had to do it on no CB Four ever. My method (see above) is a proven and safe method for diagnosis.

[Oddjob]

Another possibility is a bent float rod, it turns as the bike is in motion due to all the vibrations etc, as it turns it jams the float so it leaks, eventually the rod turns again and the float becomes free again.

You could try removing the rods and checking them and also polishing them, that's been known to help as well.

You could also make new rods, they sell the brass you need on Amazon.

[deltarider]

Another possibility is a bent float rod, it turns as the bike is in motion due to all the vibrations etc, as it turns it jams the float so it leaks, eventually the rod turns again and the float becomes free again.

You could try removing the rods and checking them and also polishing them, that's been known to help as well.

You could also make new rods, they sell the brass you need on Amazon.

If you mean the swivel pins, on our models they can't get dislocated. Honda carefully shaped the carbs thus, that they stay shielded in the right position. Also our type of floats cannot leak. When maintenance is needed, cleaning the swivel pins is recommended. A little naphtha or WD-40 will do. Do not use anything abrasive. Swivel pins are best removed using your fingernails. If you must use pliers, I repeat must, do not pinch the pin!

[Oddjob]

If it comes out and isn't pinned in place it can move DR. They ain't a tight fit, I can pull them out with my fingertips. As they are made of brass they are also easily bent.

[Neill C]

I have previously polished the pins. I push them out with a piece of stiff wire. If it overflows again I'm going to remove it to see if it's bent as that would make sense.

[Multiman]

I had problem with overflowing carbs that had just been cleaned and rebuilt using new brass float needle valve seats.
After a lot of cursing it turned out that the new brass wasn't the same dimensions as the old brass and therefore the o-ring wasn't sealing properly
I put some old brass in and the torrential overflow problem stopped straight away, so maybe check the valve seats are all the same?

Old on left, new on right. O-ring groove at slightly higher position on the new.

[Neill C]

That's very helpful. Thanks. Maybe it seeps past the o ring with the vibration of the engine.

[deltarider]

If it comes out and isn't pinned in place it can move DR. They ain't a tight fit, I can pull them out with my fingertips. As they are made of brass they are also easily bent.

IIRC, when the carb is assembled, like in normal daily use, the design of the bowl prevents the pin coming out.