Topic: CB650 accelerator pump problem

[jerrit1]

I rebuilt the carbs on my 1980 CB650 Custom (non CV carb) but did not replace the accelerator pump diaphram/rod.
Bike starts and Idles fine but dies when i give it gas....i noticed fuel does not squirt when i give it gas so im sure the accelerator pump is not working, I removed the pump houseing from carb #2 and there was gas in there.
I blew air through all the holes and got air....the rubber gasket has the 2 holes that it should and the arm pushes the AP rod down (about 3mm) when the throttle is opened. I'm stumped.
also the rod to arm gap looks about right (.08mm)

please help

Thanks,

Jerrit

[my78k]

Did you double check the spring placement? Sounds silly I know but when I reassembled mine I had the spring in the wrong spot...

Dennis

[jerrit1]

I pulled the carbs and checked everything again.
I removed the carb bowl from carb #2 and filled it with gas then pushed on the shaft of the diaphram...no fuel was forced up through the hole that the fuel should be forced up through...not sure why, I checked all thos holes with an air compressor....the fuel does flow into the accelerator pump and with compressed air I could feel air blowing out all the holes as it should....but fuel wont squirt.  im stumped!

[TwoTired]

The hole that feeds gas to the diaphragm has a check valve in it and so does the hole on the exit side of the pump.
When the pump sucks gas in, the out put valve should shut.  When the pump feeds gas out, the inlet valve should shut.

If you can push fluid both ways through either of those passages, you know why the pumps doesn't.

Cheers,

[jerrit1]

Is the check valve the tiny square brass looking thing in the fuel passageway?

[TwoTired]

The check valve is BEHIND that square brass plug.

I've never actually seen it, really.  But, I know it is there, and believe it is a ball device.

Cheers,

[jerrit1]

opps, I hammered out the brass plug thinking it was clogged up...didnt see any spring or ball...I didnt remove the one in the bottom of the AP cover...just the one in the float bowl as the gas would move up twords the carbs.

[TwoTired]

Dunno what to tell you. I've cleaned all the ones I've seen with carb fluid until they would only pass it one way.

Good luck!