Float Height Issues

[bjones]

I have scratching my head trying to figure my float height / overflow problems with my 83 550L.

I set the float height to the recommended 22.4mm (no gasket) on both carbs. When bench testing with fuel to the inlet with a funnel, one of the the carbs overflowed.

Reopened the carbs and verified that with the carbs inverted, I could not blow air into the fuel inlet, the valves appeart to be sealed tight. Wouldn't this be an indication that the valve and seat are ok and sealing properly?

I rechecked the height and it was right at 22mm. I then experimented with what it would take to stop the overflow. With the float level set at 26mm, there was no overflow.

I stupidly went ahead and installed in this condition just to see what would happen. The result was an extreme hanging idle which I am guessing is due to running lean as a result of the high float height?

Now I am back to my original problem, overflow when float height is (seemingly) correctly set and the float valve/seats (appear) to seal.

Am I fooling myself by inverting the carbs, blowing into the inlet and observing that no air flows? Is this a false test for valve/seat wear?

Any suggestions are appreciated.

[Gorminrider]

have to go through some of the ones you've already checked no doubt...?...are you sure there's no leaks in the floats themselves(shake them to test for fluid inside) and that the tiny springs in the float needles ends are functioning freely...these problems would satisfy your symptoms and tests.
picture here from
from Ed Ness's "Mikuni BS (CV) Carburetor Rebuild Tutorial" available BassCliff's site


there was a recent similar thread here:

http://www.thegsresources.com/_forum/showthread.php?t=202532

typically, I never heard what was wrong, but there's some good ideas
here's just one:

http://www.thegsresources.com/_forum/showpost.php?p=1777967&postcount=11

you might want to swap needles temporary-like to see if that makes a difference
is it remotely possible the seat itself is not sealing against the body of the carb? therefore, however good the float needle+seat match is, your carb will still overflow...

PS, I always do the blow test too but just because I can't resist. It sure alerts to a gross problem

[Agemax]

if you went from 22mm to 26mm and it cured the problem, try going to 23mm and see if that helps, without the idle problem. go up in 1mm increments and see if you cant sort a happy medium

[Guest]

Now I am back to my original problem, overflow when float height is  (seemingly) correctly set and the float valve/seats (appear) to seal.

Am I fooling myself by inverting the carbs, blowing into the inlet and  observing that no air flows? Is this a false test for valve/seat wear?

A static test is not always accurate. Set the height properly, put the carbs on the bike and ride. You will have vibrations and bumps that will most likely seat a temporarily sticking float needle. I just rebuilt a set of carbs for my bike. A needle on one carb stuck two or three times. I tapped the bowl with a screwdriver handle several times to seat it and after riding for a while it never did it again. This has happened to me on several sets of carburetors, so I can't believe it's all that unusual.

[bjones]

Thanks everyone.

Gorminrider:
I can verify that the spring-loaded needles appear to be "springing" freely. When the carbs are inverted the tabs rest on the needle without depressing it. Slight pressure on the float results in the needle depressing further, compressing the spring.

I have decided to order a new pair of needles and seats from Parts n More. Saw them recommended in another thread.

When they arrive I will install, reset the floats, retest and return and report.

Thanks again

[bjones]

It's been a while but I am still fighting this issue.

I have replaced the needle, seat and float on the problem carb. I again set the float height to 22mm above the gasket.

On re-install the carb overflowed. This time I had clear tubing attached to the bowl drain and could clearly see the fuel level rise above the gasket surface.

Without taking the carb off the bike, I pulled the bowl and began adjusting the float until the fuel level was 5mm below the gasket surface when the bike was upright off the stand. Trouble is, this resulted in a significant bending of the float tang and the level is obviously not 22mm.

I am tempted to call it done and ride but it bothers me that I had to do this. Something is wrong here but I am missing it.
Also, the hanging idle I describe in the original post after messing with float levels appears to have been unrelated. New o-rings seems to have cured that.

Any suggestions?

Thanks again.
Bruce

[george g]

Float issues

Bruce, I was up till 3AM this morning fighting the very same problem. I have a 1980 gs1000 bought in a basket. It came with new rebuild kits which included these spring loaded needles that you have mentioned.
I have been adjusting inverted,to the point where the tang touches the beginning of the spring load. I this what you are doing also? I wonder if we should be adjusting to the compressed spring level? Any one else?
Thanks!
george g

[Guest]

The generic rebuild kits come with HORRIBLE needles. throw them in the garbage can. If at all possible, use the ones that came with the bike. even in poor condition, they are much better than a rebuild kit.

The ONLY thing the rebuild kits are good for is the gasket, which you don't need because you can reuse them if you are careful.

Buy o-rings from cycleorings.com
Buy MIKUNI or Suzuki pilot jets, needles, etc. from bikebandit, Dennis kirk, or whatever.
You can get the rare stuff from http://www.motorcyclecarbs.com. Don't waste your time with the website, just call him. he has more parts than you can imagine. or else someone from the forums can get for you.

[bjones]

Success!

OK, a few things I have learned.
1. I will no longer trust float height as a measure of fuel level at least as anything other than a starting point. Always check the fuel level with tubing attached to the bowls.
2. When one carb is overflowing in a multi-carb system, do not assume the overflowing carb is the problem.

So as stated in my last post, I had used tubing attached to the bowl drain to set the float tang position. I did this only on the leaking (left) carb. Lo, the carb still overflowed after idling for a bit.

A bit more background, the overflow is much more pronounced when the bike is on the stand and the leaking carb is the downhill carb.

Then, a light when on. What if the other carb also has its level set too high and is overflowing but that fuel is draining into the downhill (right) carb.

Checked the fuel level of the right side carb and found it to be too high as well and again set the float height via the clear tube method.

Problem solved.

BTW, I got my needles and seats from parts n more, worked flawlessly. I believe the were genuine Mikuni. At a minimum, they were made in Japan not China,

[george g]

old needles

Success as well!
spchips was right, and thankyou! I put my old float needles back in and stopped almost all the leaking.
george g

[bjones]

Aaargg! About to give up and sell!

Sigh, I can't win. I just don't get it.

Carb(s) still leak!
Very important item that I failed to mention previously is that this leak started after I opened the carbs to clean them when chasing a hanging idle that turned out to be bad head to intake o-rings.
I assumed that I screwed up somewhere in my reassembly and have performed the following trying to recover:

• Replaced the floats with OEM parts.

• Replaced the seats and needles with parts from Parts n' More. Unsure if OEM but they were marked "Made in Japan"

• Tested my petcock. It does not supply fuel except under vacuum and no fuel is drawn into the vac line when you suck on it.

• Set the bowl fuel level using clear tubing on the bowl drains.

• Inspected the bowl gasket to ensure no part is protruding into the bowl for the float to hang up on

• Added an inline filter between tank and carb thinking crud my be migrating down and holding needle open.

In spite of all of the above, the carb will still intermittently leak. I set the levels, fired it up and watched the levels and all looked good and stable. Took it for a 30 minute test ride, all good. Called success! Then the next day during a ride it started sputtering and a quick look showed that again, fuel was dripping out the pilot air jet of the left carb, again!

This is maddening.

I did notice that the float bowls had different numbers cast into them. I had assumed they were identical and cannot guarantee that I installed them into the same locations as original. Could having them reversed from original somehow lead to an intermittent stuck float?

I apologize if I seem a bit all over the place in my descriptions and methods. I admit, I have gotten to the point of being a bit frazzled and probably no longer (if I ever was) operating in a clear and consistent fashion.

This seems like it should be such a simple system. Floats go up, seat the needles, fuel stops. If only it were so.

[Agemax]

how do you mean fuel was dribbling out of the pilot air jet?

if the leak was float height related, then fuel would be leaking from the overflow drain tubes on the bottom of the carbs.

[bjones]

Oh my, have I been chasing the wrong problem?

When the leak presents itself I can remove the intake box to carb boots and observe fuel dripping out of the Pilot Air Jet.
I had assumed that the fuel level was rising too high and the overflow was traveling up the Pilot Fuel Jet and out the Air Jet.

This is not my carb but fuel is coming out of here:

[Guest]

Are your floats moving freely on the pin, or have you distorted the pin tube making these large adjustments without removing the carburetors? Have you twisted the tab that rests on the float needle, or is it exactly parallel to the top of the float pin? Anything out of alignment there could cause your problems. The float could be hanging on the pin or a twisted tab could be pushing the top of the needle to one side, jamming the needle.