low vac on #3 carb


Information and questions on GL1100 Goldwings (1980-1983)
  • Sponsored Links
T-Rat
Posts: 62
Joined: Sun Jan 25, 2015 8:37 am
Location: knoxville tn
Motorcycle: 1983 GL1100a & 2000 Sportster 1200

low vac on #3 carb

Postby T-Rat » Mon Aug 10, 2015 6:23 am



I just rebuilt the carbs on my 83 project GL1100 that has sat for about 8-10 years. Replaced tank and rebuilt carbs. Started it last night. It started right up and after running for a while it idled down. I hooked up my carb tune pro and started to sync carbs. #3 carb has vac so low that the meter hardly moves. Less than 8 CG/HG. I cant sync because #2 and #4 won't come down to that low a vacuum. Any Thoughts? I do have some valve noise on the right bank (Clicking) and I may have screwed up the valve adjustment.....It was late and the motor was warm so I quit for the night. Will readjust valves after work today!



User avatar
virgilmobile
Posts: 7663
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: low vac on #3 carb

Postby virgilmobile » Mon Aug 10, 2015 7:13 am

If we assume that the compression is normal/similar to the other cylinders,There may be a leak where the carb mounts to the head...Or the #3 carb throttle valve is not closing enough.Another carb may be misadjusted and closing before #3.
Loosen the link between it and the matching carb.

User avatar
Fatwing Chris
Posts: 741
Joined: Thu Oct 21, 2010 6:10 pm
Location: Ont.,Canada
Motorcycle: 2004 ABS Model Goldwing

Re: low vac on #3 carb

Postby Fatwing Chris » Mon Aug 10, 2015 5:16 pm

Did you re-install the vacuum line(what kind of shape is it in) to the advance unit on the back of the motor?
If I'da known it would last this long,I'da taken better care of it.
Chris
Double Dark
Darkside # 1602

T-Rat
Posts: 62
Joined: Sun Jan 25, 2015 8:37 am
Location: knoxville tn
Motorcycle: 1983 GL1100a & 2000 Sportster 1200

Re: low vac on #3 carb

Postby T-Rat » Mon Aug 10, 2015 7:33 pm

I bench synced the carbs before I installed them so one carb closing before # 3 doesn't seem likely.....The vacuum line seems to be ok. What I did find was that the adjusting screw on the intake valve on #3 is missing! I must not have gotten the jam nut tight when I adjusted the valve. Since the vacuum is controlled by the exhaust stroke I don't know if this is part of the problem or not. I had to order a tappet screw so it will be a couple of days before I can go further. What bothers me is the nut was in the valve cover but the screw is gone. It must be down in the crankcase. I took a magnet and fished down in the oil drain hole and couldn't come up with anything. I guess I'll drain the oil and see if it comes out with the oil and if not fish around as best as I can thru the drain plug hole. At this point I am feeling like a dumb A**

User avatar
Rokon
Posts: 17
Joined: Fri Nov 21, 2014 10:48 pm
Location: Tacoma, Wa
Motorcycle: (3) 1983 GW's: Aspy, Interstate, Standard

Re: low vac on #3 carb

Postby Rokon » Mon Aug 10, 2015 9:26 pm

[quote="T-Rat]Since the vacuum is controlled by the exhaust stroke [/quote]

I think it's controlled by the intake side.

T-Rat
Posts: 62
Joined: Sun Jan 25, 2015 8:37 am
Location: knoxville tn
Motorcycle: 1983 GL1100a & 2000 Sportster 1200

Re: low vac on #3 carb

Postby T-Rat » Tue Aug 11, 2015 4:24 am

I believe you are right.........the intake stroke does create the vacuum. ..."Manifold vacuum is an effect of a piston's movement on the induction stroke and the choked flow through a throttle in the intake manifold of an engine." I think this is the first mistake I ever made........................LOL! So this may be the problem after all....Fingers crossed!




Return to “GL1100 Information & Questions”




Who is online

Users browsing this forum: RoadRogue and 7 guests