Fuel level is off? Again?????

:blink: :blink:

Many months ago when I was restoring my nice 1983 KZ550, I rebuilt the carbs with a brand new kit after completely disassembling the carbs, did a thorough cleanup and set the fuel level correctly (or so I thought). I rode the bike around very little around the neighborhood and then stowed it away for the summer while I got busy with other stuff. I then started to notice a constant stink of gas in my garage even though I did not find any evidence of big puddles anywhere. On closer look, it turns out that my carbs were leaking again as if the fuel level was off and the gas was seeping out slowly from the partition between the lower and upper bowls. This seems to be happening for each of the four carbs, not jut one or two. I know it took me forever to set the levels correctly the last time around, not to mention the crazy number of times I had to get the carb assembly off the bike. Now why is it that the level is off again? This has me stumped. Is this something to be expected after a bit with a new rebuild kit???

Have you re-checked the fuel level via the clear tube method?
What type of fuel valve is on the tank - stock vacuum petcock or manual fuel valve?
Is there an in-line fuel filter installed?

Fuel should not leak out at the joint at the top of carb bowl no matter what the fuel level. That indicates that the gaskets are leaking in which case, assuming the bowl screws are tight, the gaskets should be replaced.

Regarding the fuel level changing - there's no way the float tangs should bend themselves. So if the tangs were adjusted such that the fuel levels were set correctly using the clear tube method, the tangs should still be set the same. If your bowls are filling above the level you had set them at, the problem most likely is related to the float valves. If the valves get dirty, they will not seal properly and they will allow excess fuel to enter the bowls even if the float tangs are set at the correct level. Since the problem is happening to all 4 carbs, it is possible that contaminants in the tank, such as rust or crud from old fuel, are fouling the float valves. Do you have a fuel filter between the tank and carbs? If not, I suggest you install one, clean the float valves (this can be done with the carbs still mounted on the bike), and replace the float bowl gaskets. After you do that , use the clear tube test to verify that the fuel level is set correctly.

In addition to a carb problem, I suspect you have a petcock problem. Assuming you have the stock petcock, it is the type that is operated by a vacuum line from the carbs. When your bike's engine is turned off, the lack of vacuum from the carbs allows a diaphragm inside the petcock to close off the fuel flow. You can easily test the operation of the diaphragm and its spring. With the engine off and the petcock in the run position (NOT "Prime") remove the fuel line from the petcock. Sit a catch can under it in case fuel drips out. No fuel should drip out. If it does, the petcock has some internal damage and should be rebuilt or replaced.

Ed

Correctly adjusted tangs on the float mechanisms are for the purpose of closing the float valves when the prescribed fuel level is reached.

In other words, it's the tang adjustment that tells the float valves when to close.

However, a leaking float valve fails to close, despite the correct tang adjustment. Thereby allowing excessive fuel into the float bowl (which may continue rising on up into the carb).

The issue is usually a leaking float valve -- not the tang adjustment.

Where the tang adjustments have been correctly set so that the fuel levels are within specs as confirmed by the clear tube test (float valves functioning as designed, and not leaking) -- the tangs generally do not spontaneously fall out of adjustment during normal operation.

Good Fortune!

Thank you for all the replies. When I rebuild the carbs, I did install brand new gaskets. There is indeed an inline filter on the fuel line.

I did have problems with leaky float valve during my early experiments with setting the fuel level. Like I said earlier, I thought I had it right the last time and it seemed to be all ok until this recent discovery with the leak.

And how is it possible to change the float valve heights while the carbs are still on the bike? And doing the fuel level check seems to be such a pain because don't you have to take the carbs off the bike to adjust the levels every single time? And the bench setting never seems to be accurate. Any suggestion on the right way of doing this would be great.

Also, for the clear-tube method, what should be the ID of the clear tube being used?

The bowls are held on with 4 screws. Remove the 4 screws and the bowl will drop off. Then you can access the floats. If necessary, they too can be removed with the carbs still on the bike. It helps to use a screwdriver bit in a small ratchet to remove and install the screws and a mirror can also be helpful. The pic below shows what I use. Ed

Check for a leaky petcock. I had the same problem with mine that was fixed with a petcock rebuild kit

Thank you 650. I'll have to give that a try.

And nick, I did rebuild the petcock when I restored my bike ad I verified that there are no problems with the petcock.

Bench setting gets you close, but the clear tube is more precise.

You have to use a clear tube with at least 1/4" inside diameter tube otherwise capillary action will alter the reading. You also have to make sure there are no air bubbles in the system as that causes errors in the reading as well.

I use about a 1 inch long piece of skinny tubing to connect to the nipple, then press that into a larger, clear vinyl tube about a foot long. As the tubes swell from the gas, they seal up quite well.

You have to take many readings and get an average to get it right. Also, you have to regularly clear the tube of gas which helps to purge air. You have to let the level rise up to the mark. If it goes past then settles down to the mark, that will result in an incorrect level.

Make sure the leaks are form incorrect levels, and not other things like a cracked overflow tube or sticking float on the float pin. The float pin should also be easily removed. The only thing that holds the pin in place are the walls of the bowl. If the pin is frozen in place, there might be some corrosion happening, or something might be bent.

Bunty27 wrote: ....
And how is it possible to change the float valve heights while the carbs are still on the bike? And doing the fuel level check seems to be such a pain because don't you have to take the carbs off the bike to adjust the levels every single time? And the bench setting never seems to be accurate. Any suggestion on the right way of doing this would be great.

....

Yes, it is kind of a pain but must be done. To speed up the process, I made a simple carb stand and used tubing & a small funnel as the fuel supply. Also to save time, you only need to use 1 or 2 carb bowl screws per float bowl. Same as loudhvx for the fuel gauge, I shoved a couple of pieces of clear tubing together. I also scored a series of 1mm marks on the tubing w a razor blade.

Hold the tubing high & next to the carb body, then open the drain screw. Let the fuel settle. Then lower it to see if the fuel returns to the same level. Do not raise the tubing - if you do, start over. Also as mentioned by loudhvx, take a couple of readings per carb.

For adjusting the tangs I made a simple float support. And instead of bending the tangs, I flexed each one a number of times by pressing down on the tang w a tool. flex flex flex flex flex, then reinstall float, do the other ones, then check the fuel level.

I got it down to an assembly line process but it still took several hours - I set each one to exactly 3.0 mm below the carb body... none of that + or - stuff for me.

Thanks everyone.

I preset the float heights based on Lou's instructions on his website for the TK-22 carbs. I'll now bench set them using the clear tube method next and see how it goes. I'll let y'all know once I'm done. Thank you.