I have a China made 125cc pit bike with Mikuni vm22 carb. The clip on needle is 2nd to the bottom noch.
Gas leaking from float bowl drain/bypass. spark plug black powdery soot. Can't start motor. Gas blows out carb air filter upon kickstarting motor.
I cleaned and blew out ports with compressed air. What should the air/fuel screw nearest the motor be set at? and the idle screw turned out from contact of the throttle piston?
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the float is not what needs cleaning.. its the needle and seat that the float controls that needs cleaning.. this is what regulates the flow of gas into the carburetor float bowl.. -- #32 on this exploded view.. http://www.carbparts.com/mikuni/vm18_144.gif
you probably let your bike sit for a while and your float is stuck in the carburetor,so try tapping lightly on the carburetor bowl at the bottom to see if it stops flowing .anyway it goes you probably looking at taking carburetor off and cleaning it out
It appears that you have what we used to call a bleeder. Where the carburetor leaks gas into the manifold past the jets. I have found instances of this in the 2nd market carburetors especially. It is possible the carb may need rebuilt and gas is leaking past the needle on the float. If not then I would recommend replacing the carb. I have always had excellant results from Mikuni on these big bikes.
The fuel needle sets in a recess in the carb. the retaining clip is attatched to the tab on the float and the needle attaches to the clip carefully install the fuel needle/float assembly into carb inster pin to retain float into carb replace rubber seal on carb. / bowl cover assemble
the needle and seat in the carb isn't seating. First, shut off the petcock, and drain the fuel bowls with the screw on the bottom of the bowls. Let all the gas drain out of the bowls.Tap lightly on the carb with a small hammer, the refill the carbs, see if it still leaks. if it does, you need to pull the bowls off, remove the float and clean out the needle and seat, and put it back together
That tube would be the overflow tube. Your carb float is sticking open and allowing fuel to flow in constantly. You need to take carb apart, clean needle valve, and inspect or replace carb float.
It is a vent / overflow hose. It drains to the atmosphere / street. If gas is coming out and isn't stopping then a float is stuck.
Turn off the gas and drain the offending carb(s). Next, turn the gas back on and sharply tap the float bowl with the plastic handle of a screwdriver as the fuel bowl refills. The goal here is to vibrate the float to free it up. If doing this process a couple of times does not free the float I would remove the carb(s) and look for any misalignment of float pin, needle or adjusting tang.
Now re-clean with a spray carb cleaner. Clean the air filter then re-mount carb(s). Next, Remove the water trap bowl at the bottom of the petcock, (gas valve). Dump it, clean it and re-mount it, ( not all bikes have a trap bowl ). INSTALL AN IN-LINE FUEL FILTER..
sounds like the main jets are partly pluged, you must remve all brass jets and seats including needle jet and its slide soak in carb cleaner and blow out with compressed air only.. hold up to bright light to verify if all are clean. jim
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