Topic: Leaky #3 float driving me insane!!!

[750K]

Ive been fighting a leaky #3 float, it's driving me bloody nuts. 77 cb750, pd41a carbs. Had them off the bike to check and set the float levels, after the first round of having levels fine one moment then puking gas out of the intake side of the carb I got new float needles.

#'s 1,2 & 4 are set with a caliper and checked with clear tubes and are perfect, #3 is still puking gas intermitantly. Dribbling one moment and pouring out the next. Does not make a difference if I bend the tab or not, I've pulled the bowl and swapped needles from the other set carbs with nothing changing. With the bowl off & pushing the float up or the needle with a finger and the gas on it doesn't even drip, I've swapped other floats from a spare set of carbs as well as a different bowl. Nothing seems to make a difference.

After running through different combos of needles, floats and bowl, as wells bending the tab on the float I'm ready to throw it all in the street and walk away. Any ideas of how to get the leak under control? I'm pretty sure the float itself is hanging up on the bowl seeing as manually pressing the float or needle with the bowl off stops any gas. The floats are the rectangular foam ones, they do float.

Driving me nuts, just trying to do some tuning and get back on the road...

[Terry in Australia]

I think you might have hit on the answer mate, I had exactly the same problem with Ken's K1 recently, gas pissed out of (you guessed it) #3, and after I pulled the carbs and swapped out the jets, float needles and seats etc, I discovered that the float in #3 was snagging on the side of the float bowl. I bent it away slightly, and it hasn't leaked a drop since. Cheers, Terry.

[ekpent]

Make sure the float is not hitting on the gasket inside the bowl also if it protrudes in a little.

[DJ_AX]

Make sure the float is not hitting on the gasket inside the bowl also if it protrudes in a little.

+1 to that too

[750K]

Make sure the float is not hitting on the gasket inside the bowl also if it protrudes in a little.

The rubber gasket on the PD's sits in a little grove so I can rule that out, good idea though. It's more of an o-ring than a gasket, I take it the earlier carbs have a fiber gasket? I'm going to mess with it more today, hopefully I can sort it out.

[Killer Canary]

Always beware of the cracked overflow tube.

[lucky]

One other thing can cause the problem.

The overflow pick up tube in the float bowl has a hairline crack.
You may need a magnifying glass to see it.
Just solder the crack shut.

[750K]

Overflow tube is fine, I checked closely. The fuel is pouring out of the intake side of the carb body not the tube, the overflow tube has the clear line on it. The fuel level will rise in the tube till it hits the height of the brass nozzle inside the throat of the carb and then pour out.

Sometimes it dribbles out, most of the time it pours. The odd time it will hold its level, either just about half way up in the bowl or just at the the gasket and sit there without a drop. Then I drain it and re test and it pukes gas again. I'm still leaning to float sticking but I can't figure out where it's touching.

[ekpent]

Is the drain tube or overflow area working and not clogged as it seems that the fuel should exit that before pouring out the carb body. Seems on one of my earkier carb 750's I had an issue like that that was fixed by unblocking the overflow circuit actually the rubber tube   PS-Sorry about the bad gasket advice,have never had one newer than 76   

[750K]

^^^ yeah ekpent, the drain tube etc is clear and working. That's where the clear tube is attached to verify fuel level, the carbs were torn apart and properly cleaned over the winter. New gaskets and orings, I rechecked all the passages last week when I pulled them off the bike to check and set float levels and re jet for a different airbox set up. Pulled the jets etc and sprayed carb clean through it all followed by compressed air, accelerator pump is working strong as hell as well. This leaky #3 now explains my slightly rich #3 plug and puff of blue smoke I've been experiencing...

No sweat on the gasket theory, I have a similar issue on my Kz's carbs and that might be what's going on. The mikuni's on it have a fiber float bowl gasket instead of an oring style gasket. Gives me something to think about

[flybox1]

First, is your tank spotless?
Are you running an inline fuel filter?
Float valves have rubber tips?

Place a clear glass under your overflow tubes.
Turn on your gas at the tank.
Loosen the bowl drain screw on #3: and let it flow.
Go grab a wood block, or rubber mallet. Bang the carb rack mount
so it dislodges the floats if they are stuck.
Turn off the gas at the tank, and after it stops dribbling, look at the gas in the glass.
Any debris?
If so, it's the cause of your leak, and you'll need to clean your tank.

[750K]

Tank is spotless and I mean spotless, I don't run an inline filter. Float needles are new as well as rubber tipped. I'm using an external tank from a clear  plastic bottle, gas is clean and new. Float needle seat has been sprayed with carb clean multiple times and blown out with compressed air, I took q-tips and swabbed the seat. No dirt or debris, when I have the bowl off and I'm manually raising the float or needle lightly there's no leaking. When the bowl is on and the gas is pouring out of the carb tapping the carb bowl doesnt seem to do anything.

[flybox1]

Open your #3 bowl drain screw and let the gas pour into a clear glass, with the gas on at your tank.
Check for debris. Take a pic of the gas for us 

[bollingball]

I have a 750 78K so we are talking about the same carbs. Check closely around the hinge and post. file or sand until smooth. The only time I had a problem like yours that is where I found it.
Ken

[750K]

I have a 750 78K so we are talking about the same carbs. Check closely around the hinge and post. file or sand until smooth. The only time I had a problem like yours that is where I found it.
Ken

Hi Ken

The more I #$%* with it the more I think the hinge/pin area is the issue. I've bent the float itself away from the wall of the bowl and away from the jet tower, doesn't seem to change anything. When I swap a float and needle from a stable carb it is still the #3 that is the issue, which ever carb I switched the #3 float and needle to are at the proper level and don't leak. I think I need to revisit the hinge posts etc, thanks.

[Killer Canary]

Could it be that the aluminum around where the seat is pressed in is corroded, allowing fuel to flow around the outside of the seat?

[ekpent]

Hate to sound like a broken record but have you switched the actual bowl around yet. To make the gas actually pour out of the carb mouth,up past the bowl instead of the overflow, towards the airbox and out the carb still sounds like a vent issue. Is that still the issue ? or is it leaking in a different location  ?

[750K]

Could it be that the aluminum around where the seat is pressed in is corroded, allowing fuel to flow around the outside of the seat?

I don't think so, I've pulled the bowl and with the gas flowing I've pushed the float gently up seating the needle. The gas flow stops and there's no leak at all, once the bowl is back on its back to leaking. The carb body isnt corroded anywhere I can find, visually in good shape.

[Killer Canary]

Maybe try polishing the opening in the seat with a cotton swab in a dremel.

[750K]

Hate to sound like a broken record but have you switched the actual bowl around yet. To make the gas actually pour out of the carb mouth,up past the bowl instead of the overflow, towards the airbox and out the carb still sounds like a vent issue. Is that still the issue ? or is it leaking in a different location  ?

I have, I pulled a bowl off of a spare set of PD's I have. Made sure the overflow/vent tube is working, for good measure I sprayed carb clean through it. When I do an adjustment and fill all the bowls I can see bits of gas in the clear tubes moving as the air in the bowls is expelled by the gas entering the carbs.

Thanks for all the input guys, any ideas are welcome. What I love about this forum, everyone is real helpful.

[flybox1]

The more I #$%* with it the more I think the hinge/pin area is the issue.

^ this.
clean and check for any burrs on the posts/hinge pin.  your float might be catching on something.

are your floats upside down?    sorry...had to ask.

[tlbranth]

Where the needle valve contacts the float tab, is there a dimple? If there is, file the tab 'til the dimple's gone or fill the dimple with solder and file smooth. Then see if it leaks. That was my problem. If you bench test the carbs, you can eliminate a lot of possibilities by switching components around and seeing which components the problem follows. A #$%* when the problem is intermittent (I have one such at the moment) but, hey, you wanna ride on a stinkin' Harley or something? No? then it's worth fixing eh!

[tlbranth]

Let us know what you find eh? It's always helpful to know how a problem was resolved.

[750K]

Let us know what you find eh? It's always helpful to know how a problem was resolved.

Will do for sure haven't had time after work to play carb whisperer, been busy with work homework and some pinstriping and gold leafing side jobs at the moment. Thursday night or Friday I should be able to get back to those damn carbs, I'll be sure to keep you all up to speed.

[Terry in Australia]

Where the needle valve contacts the float tab, is there a dimple? If there is, file the tab 'til the dimple's gone or fill the dimple with solder and file smooth. Then see if it leaks. That was my problem. If you bench test the carbs, you can eliminate a lot of possibilities by switching components around and seeing which components the problem follows. A #$%* when the problem is intermittent (I have one such at the moment) but, hey, you wanna ride on a stinkin' Harley or something? No? then it's worth fixing eh!

I like that "fix", particularly if it works. Not so keen on your Harley comment, but with such a nice name, I'm guessing you're joking.