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Carbs leak into airbox when on side stand

  • Thread starter Thread starter Big Red
  • Start date Start date
B

Big Red

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Ok so here is a bit of a back story. i have done the carbs three times in the last two years. (full dip everything) got them running great tuned using a home made carbtune.(oil in long clear tubing mounted on a board worked great). ran it all summer but had issues whenever it was put on its side-stand. midsummer pulled the carbs and checked float heights (good-i thinking). still the same issue. i have pulled them off now. for testing over the LONG winter here.

1. set them up in a vise hooked up to a temp fuel hose started putting fuel in.
2. once the bowls seemed full it still took some more gas and started to leak back out of #1. pulled the bowl found the float was sticking on the gasket.
3. trimmed gasket. re-installed bowl. tested again no leak this time. sweet found my issue. it was sticking when on and angle as the float went to side slightly.

4.while testing with no leaks. i keep adding more fuel the clear tubing shows it has fuel being stopped by the floats and staying in the tubing. i walk away for awhile and come back to see the tube(fuel inlet) empty???? i add some more it hold in the tubing. come back and hour later (empty) again and again and again x8. keeps doing this but at the same time no leaks??????? adding 20ml each time.

where is this fuel going????? again they are on a vise just the carbs not on the bike so i can see everything. #4 looks to have a little fuel at the butterfly valve but that is it everything else is dry.. the last time i tried i sat and watched the fuel just gradually go into the carbs.. i even turn them to match the angle of the bike if it were on it's side stand (nothing) no leaking i have a sheet of wood under it so i would see any leaks if they happened???

any ideas?????
 
When you did your rebuild(s), did you replace the float valves?

Might be about time to eliminate the possibility that they might have given up.

Best place I have found for float valves (and seats) is Parts-n-More. Scroll down about half-way, you will see them.

Take a look around, you will likely find a BUNCH of other stuff you can use, too. :D

.
 
How would the needle get worn out as it is a metal piece. my big issue is where is the extra gas going to. i am getting no leaks with carbs in a vise and they just keep taking more and more gas. i have them empty right now to confirm the float heights on them.(when it gets a little warmer. (-30C is not fun to be out in the garage even if it's a little heated) I will also check the needles. the next major test will be to fill the bowls. drain one. take the bowl off and hold up the float then add fuel to see if it leaks into the bowl area. (doing for each carb)
 
I have seen my share of worn out needles. They get a ring in them where they sit in the seat. They will not seal with the ring.
 
I replaced all the O-rings last spring. everything worked great all summer but for two thing. Plugged fuel filter(gone now) and never being able to put it on it's side stand. when it was nothing would happen until i tried to fire it up and then the gas would come pouring out of the over flow and the airbox. also lots of misfiring as the cylinders would get to much gas and flood. I will look at the needles to see if they have and ridges out of the ordinary.
 
Ok so pulled the needles out this weekend they look to be in perfect condition no ridges or any imperfections at all. any more suggestions?
 
I don't know this model well, is there a vacuum petcock? if so is it working properly? might explain why fuel was coming out while on your side stand. As for where is the fuel going, well if it's not leaking out then your carbs then the only thing that is happening is that your carbs were not full yet, your carbs take a lot more than 160mls to completely fill up. I'm curious to know how you are measuring your float heights and what setting you have them at. The very best way is with the a clear tube, and you can make your own if you don't have the fancy adapter. Just throwing some ideas out there.
 
Replace the needle and seats as an assembly on all 4. Should cost about $45. Just did it myself on my GS850GL.
 
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Not sure if your floats are hollow .....

Have you checked that the floats all weight the same and do not have fuel in them from a small hole? that would explain where bench stand fuel is going and why a float(s) does not come up to full closure under normal use.
 
Hello there. I feel a bit better about my weather now.

We share bike models, mine is two years younger but I believe same setup motor/carb wise. I had same issue when I first got mine except my carbs leaked into crank case. As some else mentioned, bad valve(s). Note that the needle is only half the valve, the seat is the other half.

Only way floats could be getting stuck on the bowl gasket is if the float(s) plate (per carb there are two floats attached to a plate) is bent which can happen easily. On the BS32 Mikunis I believe you have the floats are not hollow. Obviously gas can't just vanish.

Liquids evaporate, how fast, how much, under what conditions, could not tell. Likely your carb bowls aren't as full as you think or they are leaking out, those are the only options, though I once knew a guy who would drink anything :eek: I suggest take a wholistic approach, take your time. Install new valves, i.e., needle and seats, make sure float plates are straight and true, adjust floats to spec, reassemble and use recommended clear tube attached to bowl drain ports to confirm fuel levels. Btw, from bad experince, carburator cleaner will srink and dry rubber, o-rings, plugs, etc.

That's what I did to solve my problem. Also someone else mentioned make sure the tank fuel valve is not in prime and not letting fuel out w engine off. I believe not an issue if the carb float valve seats are working but could certainly compound the problem if they aren't. Just disconnect the fuel hose from the tank see if fuel comes out.

I hope that helps. Good luck
 
vacuum petcock is working great no leaking

Floats are fine not sure if they are solid or not but they are all the same in weight.

float height were measured when being assembled.

i will look into checking float height using the clear tube.

I will also try and measure the amount of fuel going into the carbs when i add to see how much it takes and report back.

the stuck float i had originally was my own fault as i cut my own gasket and left it a little wide so it would catch the float. it has been trimmed since.
 
Ok so i put everything back together filled the bowls and added more then #4 was leaking this time. so i drained that one bowl and removed it. held the float up with my finger and added fuel. this time it continued to leak into the where the bowl would be. (uh oh). i have since drained all the bowls. next step will be to remove float and needle and seat to see if something is sitting wrong or broken. does anyone have tips on removing the seat as i always have troubles????
 
Be sure the floats are in the right way too. Theres a bent tang at a 90 degree that rests against one of the float posts..be sure you can see it when the float is installed.

Needles may look fine but the brass float seats can be worn and leak past the needles.

Be sure the gaskets arent hitting on the floats as you move them up and down.

Be sure the float pins arent bent..these can make a float hang up a well.

Be sure there are gaskets between the float seats and the carb body..if not theres a leak situation area.

If you have metal floats take them and shake them next to your ear to listen for liquid inside them sloshing. This signals a leaking float which will keep the fuel on no matter what.

If you have poly carbonate floats theres no weighted float issues.

To remove the seats..DO NOT SQUEEZE them with pliers. This can make them ever so slightly out of round and the float needles will drag and then your screwed. Remove them by using a GENTLE grip and a twisting and pulling motion as low on them as you can grab. I use my hemostats and once theres a little gap between them and the carb body a thin blade screw driver will extract them. Use a prying motion and dont twist the blade and make gouges in the surfaces. A little WD40 will lube the orings and help too.

If youve already did the pliers grip be sure the recess for the needles are round and the needles will spin 360 when inside the holes. If they dont spin around inside there and not drag or hang up youve got it out of round...This may be your problem.
 
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"To remove the seats..DO NOT SQUEEZE them with pliers. This can make them ever so slightly out of round and the float needles will drag and then your screwed. Remove them by using a GENTLE grip and a twisting and pulling motionas low on them as you can grab. I use my hemostats and once theres a little gap between them and the carb body a thin blade screw driver will extract them. Use a prying motion and dont twist the blade and mke gouges in the surfaces. A little WD40 will lube the orings and help too.

If youve already did the pliers grip be sure the recess for the needles are round and the needles will spin 360 when inside the holes. If they dont spin around inside there and not drag or hang up youve got it out of round...This may be your problem."


Good tip Chuck.
 
If I were you I'll get a new set of o-rings for the needle seats in any event but specially if you've ever used carb cleaner to clean carb passages with the seats installed. Btw/Hard to tell condition of rings by looking but if you notice allot of seat play once the clamps are removed then they are toast for sure.
 
all the orings were replaced last winter when i did an over haul on the carbs. the seat have no play in them at all in fact that is why i have not tried to remove them yet. getting warmer this week so i will be doing some more work on them later in the week.got them back together again and the same thing is still happening again now. leaking when on an angle. the big float/needle issue is fixed. (i guess i was tired when i put it back to gether last time i had the needle upside down) oops. it seems the the fuel is coming out of the pilot air jet of carb one.
 
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