Pulse Generator/Vacuum Advance - Steve Saunders Goldwing Forums

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post #1 of 5 (permalink) Old 03-25-2005, 06:25 PM Thread Starter
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Does anyone here understand the working of the ignition timing vacuum advance on a GL1100? I searched the archives, but didn't find what I was looking for.

I have suspected that this unit was not advancing the spark properly with the vacuum diaphragm. I disconnected the vacuum tube from the carb and found that the port was not producing any measurable vacuum, so I connected it instead to one of the ports on the inlet manifolds. Engine speed increased and acceleration was better, except.... there was a constant ticking noise coming from the pulse generator, which I assumed was a result of the "pulsing" vacuum produced by the port on the inlet manifold.

What is the source of the vacuum at this additional port on the carb? Does something need cleaning out in order to give me a vacuum for the pulse generator? Or should I ignore it and feed it from an inlet manifold and puta restrictor in the line to even out the vacuum?

Any words of wisdom would be much appreciated.

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post #2 of 5 (permalink) Old 03-26-2005, 10:53 AM
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It still sounds like a faulty vacuum unit. Even a dead one will pull some vacuum from the manifold, ust not enough to run well.

Ted Kelly.
Current Wings; 2006 GL1800 & 1997 GL1500se.
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post #3 of 5 (permalink) Old 03-26-2005, 12:47 PM
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Did you try cleaning out the carb port? Should be sufficient vacuum there to run things since it was designed that way. How about the possibiity of a vacuum leak there?

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Past 'Wings: GL1100, GL1200, GL1500, GL1800

Current BMW C650GT
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post #4 of 5 (permalink) Old 06-25-2005, 12:42 PM Thread Starter
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I'm still struggling with this vacuum advance problem.

I bought a new unit off Ebay and now I understand how it works. The one on my bike does not hold a vacuum. I can suck on the tube and then hear the click as the spring return pulls it back. I checked the tube for holes etc. I guess this means a hole in the diaphragm.

This means that I need to install the new one. Can anyone tell me if this is possible without removing the rear wheel and swingarm. Also, if I go to all that trouble, will I really notice any improvement in performance.

Any comments gratefully accepted.



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post #5 of 5 (permalink) Old 06-25-2005, 03:42 PM
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I've just been looking at my vacuum unit 'cos I've got trouble with my starter motor (it makes sense if you follow the thread on this forum).

Anyway, just done the same thing with mine. I suck and hear the click you describe, then nothing until I let go when it drops back. I guess yours drops back on it's own?

I think the only alternative to removing the rear wheel/swing arm is to remove the engine.


1990 GL1500 SE
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