One day you are standing near your Honda CH250 scooter and
smell a strong odor of gasoline. Removing the side covers, you
cannot see any gasoline dripping from the carburetor but there is
a strong gas odor. You start your scoot, and gas comes pouring
out of the overflow vent tube on the carburetor. You quickly shut
her down and scream, "What's going on?"

In the bottom gasoline bowl on the Keihin CV carburetor is the
plastic bowl float and aluminum float valve. The valve rests
inside a bracket on the back of the plastic float and is
removable. A pin holds the float allowing it to lower and raise
when gas fills the bowl. When filled with gas to capacity, the float
raises and closes the valve which seats against the gas fill port
preventing excess gas from entering the bowl when filled.

Excess gas will fill the bowl and run out the overflow under two
conditions. Firstly, if the plastic float breaches a seam and fills
with gasoline and loses its ability to float or secondly, if the float
valve, which has a tiny 1/4" long spring and 1/8" long push-type
pin, separate and fail. Usually, the float will be good. However, if
you see gas sloshing around inside or if submerged in water, it
fails to float, you must either repair it with shellac or replace it.
Replacement floats cost about $32.

The float valve costs about $20. However, it also can be repaired.
If you have been careful in removing the gasoline bowl and
separating the valve from the plastic float, the tiny spring will still
be inside the valve. The push pin will be lost possibly drained
out the carb. Take a large metal two inch paper clip and cut off a
1/8 piece and insert it into the valve above the spring. The spring
will allow it to compress and fit snugly onto the back side of the
float. Reassemble and test. The float should bounce slightly
before bottoming out. This repair costs next to nothing and will
provide years of reliable service. 

Randy Pozzi (Rev. 04/2004)