The GL1100 accelerator pump

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Early 'Wing Guru
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The GL1100 accelerator pump

Post #1 by mikenixon » Thu Jul 06, 2017 3:36 pm

On Keihin VB series carburetors, which of course include the GL1100, a kind Catch 22 exists. First, the engine won't work well without the accelerator pump circuit doing its job and doing it vigorously.


But, 30 years now down the road, this is the circuit in this carburetor that is the most difficult to bring to complete health during a rebuild. I have even had to replace individual carb bodies (castings) whose accel nozzles could not be unblocked. Not with heat, not with chemicals, not with hydraulic pressure, and not with ultrasonic. I have tried various means over the years but have pretty much settled at present on the method shown here.


I'm using a long (over 12") tool which terminates in a tool steel wire. The length allows room to get light in at the same time. The final not-so-clear picture is a closeup of a GL1100 carb with both its throttle and choke plates and shafts removed. Note the wire entering the accel discharge nozzle, where it is rotated and worked in the nozzle until the blockage is overcome. I find I have to do this on maybe 30 percent of the accelerator pump equipped Keihins I rebuild. I also have checks and tests and special techniques for optimizing the accelerator pump check valve bolted onto the bottom of the carburetor. It's important to take the time to make this circuit work its best.

Mike Nixon

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