QuestionI am working on a cb 750-all 4 float needles leaked and I have replaced them all and they still leak at idle-it has plastic floats and all are good-they are non adjustable-the only pressure is the tiny spring inside the needle itself, why are they not sealing or is there a fix to get more float pressure agains these needles? Please help-Thanx.
AnswerWes,
it doesn't normally take much
pressure to close a float valve.
Have you checked for debris
in the fuel tank or lines?
Add a lawn mower or other fuel filter.
Some of these carbs have o-rings
on the float valve seats.
These are press-in type valves
and if the o-rings leak it is
the same as if the needles were leaking.
Do all the carbs leak?
Could be a plugged gas cap
vent causing pressure in the tank.
This would affect all the carbs.
Between all the carbs there are
fuel joint pipes. These
also have o-rings that could leak.
Are you sure it is the float valves?
Poor carb kits, bad gaskets,
and leaking or plugged carb
air vent tubes or passages are about all else
I can think of.
Pull a float bowl and see if the fuel stops
when you lift the float.
See how much pressure it takes.
Does it still leak?
The float level is about 15mm I believe.
The fuel level should come up
close to the mating surface of the
carb and float bowl when correct.
Has anybody changed the floats?
Could they be the wrong parts?
The old bikes used to get warped
float bowls from overtightening the screws.
It's not common now though.
