How to test a carburetor overflow tube for leaks (Harley-Davidson Keihin CV40 pumper carb)

A cracked carburetor overflow tube (standpipe) will result in a slow leak from the drain outlet of the carburetor. The video shows how to test the overflow tube by filling the float bowl (float chamber) and pressurizing the drain outlet (e.g., with a hand pump or an air compressor using a very low pressure setting around 5 psi) while plugging the inlet of the overflow tube. If you see bubbles, the overflow tube has a crack. If the overflow tube does NOT leak, but fuel is still coming out of the drain outlet of the carb, there is a problem with the float valve. I fill the float bowl with gasoline, not water or other liquid, to avoid introducing anything other than gasoline into the accelerator-pump chamber.
constant velocity
leaking problem
mechanical slide
overflow
Honda
Yamaha
Kawasaki
Suzuki
HD, H-D, constant velocity, repair, Dyna, Softail, FXR, Super glide, Low rider, Sportster, FLH, Ultra, Road King, Harley Davidson, CV carb leaking gas

[@robfox5562]

What’s is carborator?

[@Zerk_Ziegler]

If the question is "what brand", the answer is in the title of the video. The information applies to any carburetor with an overflow tube (standpipe). If the question is what is a "carborator", then I have no idea.

[@jinz0]

hey when I put my bike fuel to 'on' it drips abit is that supposed to happen? If I put 'off' it stops@@Zerk_Ziegler

[@Zerk_Ziegler]

@@jinz0 Not supposed to happen. Your float valve and/or your overflow tube (if you have one) is leaking.

[@jinz0]

@@Zerk_Ziegler if I buy the carburetor kit will it fix it? Or just need new overflow tube? It's an old cb125 Honda, 1983 and can't find a good motobikes service place near me

[@Zerk_Ziegler]

@jinz0 Test the overflow tube first and then test the float valve to find out where the problem lies before you start spending money and throwing parts at this carb. I have some vids that should help as far as testing of the float valve is concerned. I strongly recommend NOT using aftermarket rebuild kits, especially when replacing the float-valve needle -- factory parts are best. Also, it's a good idea to use JIS (Japanese Industrial Standard) screwdrivers to remove the hardware from these carburetors -- they fit the screw heads much better than conventional Phillips screwdrivers.