Bad Vacuum Advance?


Information and questions on GL1100 Goldwings (1980-1983)
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mclark38
Posts: 23
Joined: Thu Oct 25, 2012 8:53 pm
Location: Green Bay, Wisconsin
Motorcycle: 1982 GL1100I Interstate

Bad Vacuum Advance?

Postby mclark38 » Tue Sep 24, 2013 11:45 am



Hi guys,

I believe I have a bad vacuum advance or atleast a sticking valve of some sort inside of it. Last week my GL1100I ran great up until I came to a stop light and had to sit for a little bit. The bike finally warmed up while I was sitting there. When I took of it had very little power and ran very very rough and was jumping forward like it was just about out of gas. I got home and remembered that when I first got the bike and took it to a mechanic to get the carbs cleaned that he said something about he pulled off the vacuum line from the carbs and sucked on it which caused the valve to open in the vacuum advance, which made it run much much better. Ever since I pulled off that line and sucked on it to trip the valve its been running rough at low RPMs. Can I just shoot some kind of lubricant down the line to solve this or do i need to replace the whole assembly this winter?

Thanks,
Mike



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virgilmobile
Posts: 7660
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Bad Vacuum Advance?

Postby virgilmobile » Tue Sep 24, 2013 12:54 pm

When I took of it had very little power and ran very very rough and was jumping forward like it was just about out of gas.


The vacuum advance part of the system does not operate at a low rpm.
This rough running from a idle is not related to it.

he pulled off the vacuum line from the carbs and sucked on it which caused the valve to open in the vacuum advance


This method is to test if the vacuum advance actually works..
The vacuum canister is a diaphragm sealed under the cap...do not spray anything into it...

Under normal conditions....(this is close)...
the 1100 has ignition timing at 10*btdc at 950 rpm...
it will increase up to near 23* btdc by the mechanical advance system..
it can increase to 38* btdc max combined mechanical and vacuum...
The vacuum is proportional to air flow.
It is ported before the throttle plate...
At a idle,there is no vacuum at the canister...
The timing changes as the vacuum on the canister increases to 1.6" and stops advancing at 3.5"
This vacuum will show only as the engine is revved up...never at a idle...

By your description...you have trash or water in the carb....
Start the bike from cold...idle only for 5-7 seconds..regardless of how bad it idles..do not rev it up...
Shut off the bike and lightly tap each header pipe...I'll bet 7 cents that at least one pipe is cold...

mclark38
Posts: 23
Joined: Thu Oct 25, 2012 8:53 pm
Location: Green Bay, Wisconsin
Motorcycle: 1982 GL1100I Interstate

Re: Bad Vacuum Advance?

Postby mclark38 » Tue Sep 24, 2013 1:54 pm

virgilmobile wrote:By your description...you have trash or water in the carb....
Start the bike from cold...idle only for 5-7 seconds..regardless of how bad it idles..do not rev it up...
Shut off the bike and lightly tap each header pipe...I'll bet 7 cents that at least one pipe is cold...


I'll give this a try after it cools down. Its been running great today. A little rough this morning until it was entirely warmed up but that's expected. Was going to start running Seafoam through is pretty soon before I put it away for winter anyways so maybe I'll start that right now.

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virgilmobile
Posts: 7660
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Bad Vacuum Advance?

Postby virgilmobile » Tue Sep 24, 2013 2:04 pm

One day after my bike had been running flawlessly for a few months,it wouldn't fire on one side at a idle.(gl1500..2 carbs) but would fire at half throttle(just scary)....I finally got to work...

I opened the drain on the offending side,and with some compressed air blowing into the vent tube,it belched a teaspoon of water gunky stuff out of it....

Runs fine now..
Louisiana humidity condensed in the vent pipe and got sucked into the bowl...I've sense added a extension and a filter to that pipe...no further problems..

Remember we are now using that "special" gas...It can accumulate water in unwanted places.

mclark38
Posts: 23
Joined: Thu Oct 25, 2012 8:53 pm
Location: Green Bay, Wisconsin
Motorcycle: 1982 GL1100I Interstate

Re: Bad Vacuum Advance?

Postby mclark38 » Tue Sep 24, 2013 2:18 pm

virgilmobile wrote:Remember we are now using that "special" gas...It can accumulate water in unwanted places.


I've been trying to stay away from it as much as possible. About 95% of my gas is premium no-ethanol

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virgilmobile
Posts: 7660
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Bad Vacuum Advance?

Postby virgilmobile » Tue Sep 24, 2013 2:21 pm

Great...Hopefully what ever it was got sucked through the system...Mine was so bad it plugged the slow speed jets...




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