Need help from some 1200 carb gurus


Information and questions on GL1200 Goldwings (1984-1987)
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G-Wiz
Posts: 40
Joined: Wed Jun 15, 2016 11:31 pm
Location: Bellingham, Washington
Motorcycle: 1984 GL1200 Standard

Need help from some 1200 carb gurus

Post by G-Wiz »



I am trying to determine what to do next with my bike. I have been having fuel mileage issues since putting it back on the road. Rebuilding the brake system gave me maybe 2mpg but I am still going through gas like crazy. I checked my plugs last night and again today and #1 looks too rich. All the rest are even and normal. There is a faint fuel smell in the crankcase but the oil level is perfect. Idles smooth at 1k. Doesn't stumble or backfire unless the choke is on. Carbs rebuilt and synced last summer although I only have 2 guages so I did two at a time. Topped off tank twice this season. Both time it was half a tank and only 40 miles on the ticker. No actual fuel leaks present. I work at a local Napa store and although I have more bike experience, I work with some of the best auto parts/mechanics in town so we started brainstorming ideas. 1st was the tear in the diaphram which is just at the circular portion under the cap (if that makes sense to anyone). 2nd, float levels. Checked, rechecked, and rechecked again last summer when I did the rebuild but still a possibility. 3rd, bad ignition coil. Kinda makes sense but its only on one plug. Thinking of swapping the two to see if it changes. 4th, bad plug(s). I have a spare set i'm going to swap in tonight to see if it changes. Only a couple hundred miles on the current NGK DPR8ES's that are in there now though. 5th, air cutoff valve but why only rich on one cylinder???? I have not checked the compression yet as I don't have a good tester. Making excuses for being too cheap to buy one but time to bite the bullet. ANY ideas on where to go from here? I am seriously stumped.



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G-Wiz
Posts: 40
Joined: Wed Jun 15, 2016 11:31 pm
Location: Bellingham, Washington
Motorcycle: 1984 GL1200 Standard

Re: Need help from some 1200 carb gurus

Post by G-Wiz »

Crap I almost forgot. 1984 Gl1200.

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ekvh
Posts: 409
Joined: Thu Apr 29, 2010 9:52 am
Location: Grand Forks, ND
Motorcycle: 1977 gl1000

Re: Need help from some 1200 carb gurus

Post by ekvh »

Check to see if choke-( enrichment valve) is fully closing. I had a set of V65 carbs ( same as 1200 carbs but bigger) where the choke plunger was not fully retracting. If you operate the choke lever while watching the cabs you'll see what I mean. If dirty they can stick and not go back in all the way.

They can be removed and cleaned still on the bike. Easier on the bench.

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G-Wiz
Posts: 40
Joined: Wed Jun 15, 2016 11:31 pm
Location: Bellingham, Washington
Motorcycle: 1984 GL1200 Standard

Re: Need help from some 1200 carb gurus

Post by G-Wiz »

Checked the choke and all is functioning normally. Thanks for the advise. Would have overlooked it otherwise. Had my fried check out the fuel pump and all is good there. Just checked compression and all cylinders are between 180-182psi. Gonna pull the carbs again and check everything over.

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G-Wiz
Posts: 40
Joined: Wed Jun 15, 2016 11:31 pm
Location: Bellingham, Washington
Motorcycle: 1984 GL1200 Standard

Re: Need help from some 1200 carb gurus

Post by G-Wiz »

Just an update. Have changed the air cutoff valve. Found and replaced a kinked vacuum line. I checked the floats with a digital caliper and then again with an old slide caliper from the 50s. Digital read 7.5mm, slide said 8. (They sure don't make em like they used to.) Ditched the digital and readjusted the floats to 7.5. found a lot of conflicting info on the pilot screws. Some said 2 1/2 turns, some 2 1/4, some 3, and some 3 1/2. Decided on 3. Reinstalled the carbs and started with no choke. Fired up and ran smooth with a high idle. Synced with my 2 vacuum guage setup. I know, not ideal, but I'm a broke dad with two boys who seem to grow an inch a week. I can now start the beast with no choke although it runs a tad rough for the first couple minutes and it warms up in half the time. I will be taking it on a test run tomorrow after work. Plan is to top up tank, run for thirty miles and then top up to see where its at from there. If all seems right I will do a 3 tank fuel mileage test from there. As always, any input and advice is welcome and apriciated.

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G-Wiz
Posts: 40
Joined: Wed Jun 15, 2016 11:31 pm
Location: Bellingham, Washington
Motorcycle: 1984 GL1200 Standard

Re: Need help from some 1200 carb gurus

Post by G-Wiz »

Test ride went great. My bike feels like it has a bit more power now. Only went 15 miles as it's 85* this evening and leather and jeans are a bit much. After my ride it took less than a 1/4 gallon. Throttle response is better and I don't get the deceleration pop that I used to. I think it may be fixed but time will tell. For those watching for an answer, I believe my problem was a mix of incorrect float height and a bad vacuum hose. Now on to the next new issue. Front brake light switch.

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Aussie81Interstate
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Joined: Thu Nov 27, 2014 2:34 am
Location: Penrith Australia
Motorcycle: 2001 GL1500F6C Valkyrie
1982 CX500 Turbo (Historic registration - finally)
1981 GL1100 Interstate (sold)
1988 GL1500 (sold)

Re: Need help from some 1200 carb gurus

Post by Aussie81Interstate »

I would re-sync your carbs doing a) 1&3 then b) 2&4 then left bank with right bank c) (3&4) ... so 3 balancing acts to perform..remembering #3 is your base carb which has no adjustment.

You need to get them as accurate as you can when using just 2 gauges... and do it when the bike has warmed up - you might need a small fan running onto the radiator during this process.



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