vacuum differance between banks


Information and questions on GL1100 Goldwings (1980-1983)
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BadBowTie
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1998 gl1500 se

vacuum differance between banks

Postby BadBowTie » Sat Sep 21, 2013 6:27 pm



why do i have twice the vacuum on left bank as what is on right bank. i have checked a known good motor & the right bank is correct. what would cause excessive hi vacuum on left bank?



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dingdong
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Re: vacuum differance between banks

Postby dingdong » Sun Sep 22, 2013 7:21 am

The solution is to synchronize the carbs. The throttle plates need balancing. Do a search here. There is a how to for this. The actual vacuum reading isn't important just that the readings are within 1 inch of each other.
Tom

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BadBowTie
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Motorcycle: 1981 GL1100 Interstate
1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Sun Sep 22, 2013 9:08 am

i know this. i synced the carbs on my bike with no problem. i have a sync gauge the kind with the fluid. when i hook up the gauge up the right bank reeds ok, but the left bank tries to suck the fluid out of the tubes. i do have the restrictors in the hoses. is the left bank that far out of adjustment to cause the left bank to have twice as much vacuum as the right side. i did have a valve job done on left head, timing belts, & plugs. yes the cams r in time, turned the motor over several times to make sure of this. starts fine, i just need to know y left bank is twice as hi as the right bank. i checked it against my bike & it reeds the same as the right bank on the bike i am working on.

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BikerBuck
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Re: vacuum differance between banks

Postby BikerBuck » Sun Sep 22, 2013 12:19 pm

If I remember right the how to article states a specific order (ie carbs 1-4) to follow when you sync them. my understanding is when you sync in this order the final adjustment will bring the left bank in sync with the right. I do need to reread the article again myself to be sure. Hopefully I gave correct info.

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BadBowTie
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1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Sun Sep 22, 2013 1:12 pm

yes u r correct. but my problem is that the left bank pulls the fluid all the way up the vile if i leave engine on long enough. right bank is bout 6-7 in of vac, and the left bank is bout 14-15 in of vac. like i said it will pull the fluid all the way up the vile if i let it.

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JDMAG
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Re: vacuum differance between banks

Postby JDMAG » Sun Sep 22, 2013 1:45 pm

sync 4 to 3 and then adjust the idle screw?
:? :?:
Im new to this stuff but that's what I would try.

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BadBowTie
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1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Sun Sep 22, 2013 1:49 pm

idle screw is already backed off. i think i need to sync left to right first i think. but i dont have 2 vacuum gauges.

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JDMAG
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Re: vacuum differance between banks

Postby JDMAG » Sun Sep 22, 2013 1:57 pm

I use one gauge, with a tee, and 2 pet cocks for a lawn mower. I connect one to say, 3 and one to 4. crack open the valve going to 3 just enough to allow vacuum but a smooth needle movement. I take a reading, and close the valve. then I crack open the valve going to 4 the same way, and adjust 4 to 3. then re check 3. I may do this 3 or 4 times. I do it as many times between 3 and 2 and 1 and 4.

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BadBowTie
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1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Sun Sep 22, 2013 2:14 pm

so is the left bank closed more than the right bank because it has a higher vacuum reading?

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JDMAG
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Re: vacuum differance between banks

Postby JDMAG » Sun Sep 22, 2013 2:34 pm

That's for someone with more knowledge than me to answer. But here is my gauge set up.


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BadBowTie
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1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Sun Sep 22, 2013 2:38 pm

yes i did something like that with a fish tank gang valve. i guess i will have to put that back together.

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Re: vacuum differance between banks

Postby Wingsconsin » Mon Sep 23, 2013 10:00 am

I had the same problem with the '80 GL1100 Interstate.
The left side was way off the right side and when I tried to balance them the idle just went down down until it cut out...
The 2 & 4 were in synch and the 1 & 3 were in synch perfectly but not left & right...
We rode it that way for 3 weeks and it worked OKAY, but I knew it was not right...So...
My Son (his bike) adn I got to it one day..
With a 4 guage Synch manometer we decided to do this...

I worked the synch adjustment on the left side of the bike - he was on the right side working the idle adjust screw..
As I synched the banks the idle would drop, and he would turn it up..At times it would eb up near 2000 RPM and then adjust down to 750...
We would wait for the idle to smooth out and do it some more...
Eventually we got it perfectly, working the left-right bank and making some tweaks to the rest to keep everything balanced...

Key points - 4 guage manometer...This is the one I bought...

Team work ...
Patience ..and persistence...

Results ? 10% better MPG and improved power. the old girl ran like a deer whe we got done.
Starts right up even cold...

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BadBowTie
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1998 gl1500 se

Re: vacuum differance between banks

Postby BadBowTie » Fri Oct 04, 2013 10:57 am

i finally borrowed another vac gauge & synced both sides then did the entire balance & all is good. thanks.




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