TOPIC:

I checked the service fuel level on one of my carburetors and noticed it was too high. It was the outer one so I was able to get the bowl off and adjust the float. Put everything back together and checked the fuel level with a clear plastic tube. This time it fell within specs. About 20 minutes later, i checked it again, and it was high. Now I'm thinking, is the needle valve bad?
The bike is a 1983 kz750LTD Keihin c34 carbs.

Could be just a spec of dirt in there preventing the valve from closing. Next time you open the bowl dip a Q tip in carb cleaner and run it around the valve seat. Make sure you have an inline fuel filter. Make sure you did'nt do anything to the floats when you had them off so that they are hanging on the inside of the bowl.

Not big deal if you have to replace the needle valve.

Is the carb overflowing or the bike running rough or the spark plug for that cylinder sooty ?

yes the carb is overflowing

Then probably the needle valve or dirt or the float hanging.

Time to take off the bowl and try again.

If it is a Mikuni carb BS34, replace the needle/seat assembly. If it is a Keihin CV34, replace the needle and clean the seat. Use a q-tip w/brasso or a brass tool on a Dremel (brass so you don't remove material such as you might with a steel brush tool).

Just a thought........
When you took the float off is there any chance you bent the tang in the wrong direction letting more fuel in instead of less ?

From you description probably not but might be worth checking just in case.

Give a quick glance at the actual floats. Look for any lil pinholes or cracks. I have been wrestling with this problem for quite a while now. after numerous threads and wasted dollars on mechanics. I found that my million dolllar problem was actually a faulty float. so take the float out and shake it near your ear and listen for sloshing. it could save you a huge pain. good luck

you know I did notice small imperfections on the float, i was thinking the same thing. I'm also assuming that the rubber tip on the needle is worn. Tried looking for rebuild kits on Z1 enterprises but they are out of stock. I might as well do all 4 carbs and that will wait until the winter.
The carbs are Keihin CV34.
Actually I think I just might put them in a box and mail them to wiredgeorge.

Probably just me, but I find the fuel service level adjustment utterly worthless. I made my own tool that threads right into the float with clear line, level the carbs with a level, check fuel level, adjust, check again, adjust, check again. Did this for several hours in vain. Then I finally figured it out. I could add fuel to the carb, check level, make note of level, then drain the carbs and recheck and get a completely different reading, so which do you believe? I don't because range was all over A-Z so back to tried and true static check for me.

static check???.. what is this method?

Static check isn't the correct term... the correct term is FLOAT LEVEL. This means you turn the carb assembly upside down and measure the distance from the gasket mating line with the gasket off to the top of the float. This method is fairly useless on many types of floats because the floats have been bent up so many times by folks who have not bent the tang on the float but bent the float itself... they lose their original orientation. The service fuel level method measures the actual amount of fuel in the bowl and is very accurate and this is the method we use to ensure the correct amount of fuel. It must be done with the gas left on during the check of all four floats because gas can move dynamically across the rack with the fuel shut off during the check.

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