Why! Why! WHY do my Carbs leak????

I might do a little venting here but I'm at my wits end. I've gone to hell and back with these dam carbs and I cannot seem to get them to stop leaking!!!!! I'm trying to check the float levels doing the clear tube method but carb #1 doesn't want to stop leaking every time I fill it with gas. I've done EVERYTHING. I bought new needles and seats from Len to take care of this issue. I've adjusted the tang to the point where the float is so low that it can't go any lower. I've interchanged floats and needles with carbs 2,3, and 4. I tried sanding the tang to see if it's getting caught on the needle. I've removed the seat and cleaned out everything. New o-rings on the seats. I checked for any kind of obstruction in the float bowl. There is no clear reason why carb #1 one continuously leaks every time I go to try and fill it with gas. I must have removed the bowl to check something about 20 times and nothing seems to work. It continously leaks every time I fill with gas. WTH!!!! Is there something I might have missed? Please help.

 

The floats aren't upside down, are they?

 

I would keep the float bowl off and push up on the float valve so it is closed then add a little fuel. Worth checking to see if it is sealing. Could there be a hairline crack in the carb body?

 

Thanks Franz. I tried that today and the system is indeed working. No leaks when I hold up the float. It seems to happen only when I put the bowl back on. something is preventing the float from working properly once the float bowl is on. The gasket isn't getting in the way, there's nothing else in the bowl that seems like it would be an obstruction. I tried switching floats with carb #2 but it STILL leaks. I'm starting to wonder if 40 year old floats can wear out even though they're still "working".

 

Are there any imperfections on the pin that holds the float to the posts? I read on a Kawasaki forum about float problems although l have no experience of this happening.

https://kzrider.com/forum/3-carburetor/606494-floats-for-vm28-carbs-kz1000

 

I know it is unlikely but is there any possibility the float is touching the gasket. Not much gap here on my 900f carburettors.



Anything is worth checking at this stage.

 

I will check again.

 

Is the clip on the float valve on correctly? You have done all the right checks and it's still flooding. I would take the float pin out and replace it temporary with a slightly thinner piece of stiff wire just to experiment to see if the flooding stops.

 

I was thinking about the float needle not shutting off because it could be pushed sideways slightly and remember reading it on the forum. Have a read at this thread.

https://www.xjbikes.com/forums/threads/carb-float-not-working.116806/

 

Someone brought up a good point not too long ago - if the tang for the float is bent too far (the 'stop' tang - not the float needle tang), it is possible that when the float drops it is dropping too far and the needle is allowed to get cocked and may lock-up as the float rises.

So the above paragraph is from the above thread. This is the most likely cause of the problem on your carburettor. Then again you have tried different floats haven't you.
Set the float height with a metal rule and see what happens.

 

I had the same issue with one of my bikes just a month ago. Turns out floats from two of the carbs were filling with gas and unable to rise enough to shut off gas. I know you tried switching floats but next time you get in there make sure you don't have any leaks in floats. I replaced all mine and everything good now. I also had one of my gaskets not seated properly.

 

Which clip are you referring to?
I'm not quite understanding your second idea about replacing the pin with wire. Could you explain that a little more?

 

This sounds like a possibility to my issue. Are there any measurements to how far the float should drop? In other words, how far should the float drop before the "stop tang" touches to the post.

 

It is extremely unlikely (because Mikuni designed it that way) but lets say the float was getting stuck on the pin it pivots on, a slightly thinner piece of wire (fitted for the test) might allow the float to rise and shut off the fuel flow. At least then you would know. The clip if not adjusted correctly might put sideways pressure of the float valve preventing it closing off the fuel flow. It has to be one of these problems as you have all new parts. Regarding fuel in the floats you would have to have fuel in all of the floats as you have exchanged them and the fuel is still not shutting off.

 

Can you hear if there is any fuel is inside the float by shaking it? Or weigh the floats if you have access to very sensitive digital scales.

 

Ahhhh, I see what you're saying now. The question is, how would I be able to secure the wire in between the two posts to try this experiment? I might be able to figure out somethig. Worth a try. As far as the clip, my needles do not have a clip that attaches to the tang.

This is a very odd and frustrating issue. I've tried every test including removing the bowl and holding the float up by hand so I can visually see if fuel leaks through the needle and seat, and it doesn't. But when I put the bowl back on the leaking returns and gas spills out the overflow tube. I've tested the buoyancy of the float and it works fine. The float height is fine. (23mm) The needles and seats are brand new. There is no gas getting trapped inside the float itself. There's no sign that the gasket is interfering with the movement of the float or anything else for that matter. I've changed out the float with the other floats in carbs 2, 3, and 4 and the problem still occurs ONLY in carb 1. I'm on the verge of just buying a whole new rack of carbs!

 

I can sympathize, I had the same issue with a set, very frustrating.
Try lifting your fuel source higher so you have more static head pressure.
Empty #1 bowl then fill again with the higher head pressure and tapping the bowl as it fills.

 

I had the same problem with Mikuni carbs on my Turbo. Do you have aftermarket float needles or OEM? It turned out that the aftermarket float needles fit just enough differently that if the float drops too low when filling the bowl when it tries to shut the fuel flow off it is at just enough of an angle to not seat and seal correctly.
If you look at the float itself there is a tab that limits how far it can droop when filling. Adjust this tab to allow only a tiny bit of droop and try that. It does not take much movement at all to allow enough fuel flow to be adequate. I do not have pictures to offer, sorry.
I cannot take credit for this as I found it on line somewhere while equally frustrated with my Turbo carbs doing the same thing.

 

To use stiff wire you would have to cut it a bit longer than the factory pin and bend each end down against the outside of the posts. Make sure you have enough clearance for the float bowl. But then again you don't need to use wire, in fact a pin used by carpenters would suffice providing it is just slightly thinner than the pin you have fitted. You don't want it too loose just slightly thinner than the factory pin. Or use a small lost head nail just to experiment. Some of these pins/nails have small heads which you can file down to flatten them a bit. As long as the head of the pin clears the float bowl you can cut it to the same length as the factory pin. That way you can test and see if the fuel stops flowing. It is easy to push the float up by hand but if that factory pin is binding then the float cannot rise.

 

Whatever you do be careful, you don't want those posts breaking.

 

Just out of interest when you have been experimenting with different floats on the leaking carburettor have you been using the same factory pin?

 

I figured it out. I owe this one to Franz. It was a combination of an old crusty hinge pin and it being old and crusty inside of the hinge itself.

I had ordered some new floats just to see what happens and they came with new pins as well. They had a chrome finish to them as opposed to the ones already in the carbs which were dulled and old. I installed the new ones and the problem went away ONCE. On a second try the leak returned. So, I took some polishing compound and a q-tip and I put the q-tip in a drill and polished out the inside of the hinge. Problem is now rectified, and I can measure fuel levels.

It's amazing how delicate these things can be. Before I fixed the problem, when I would push on the float itself there was absolutely no indication that the float was binding in any way, none at all. I've been dealing with this issue for over a year and a half and never thought to change the hinge pin. It just didn't seem like an issue. Very humbling experience. Thanks for everybody's help and thank you Franz for directing my attention to the hinge pin.