carb sync change mystery


Information and questions on GL1200 Goldwings (1984-1987)
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jtimgrant
Posts: 77
Joined: Sat May 25, 2013 7:24 am
Location: Greensboro NC.
Motorcycle: 1987 GL1200 Aspencade

carb sync change mystery

Postby jtimgrant » Sat Aug 31, 2013 3:30 pm



I've been through my carbs numerous times due to small amounts of trash that had collected in the fuel pump. I finally put a Mr. Gasket filter in the pressure line hoping to eliminate the problem. I noticed on occasion the idle speed would drop a couple hundred rpm's. I blamed it on trash and would remove and clean the carbs but I never found any trash. This past week it dropped again so I checked the carb sync first and found the left to right bank off considerably. Cylinders 2&4 were perfect but 1&3 were slightly out but left to right were seriously off. This had happened several times so I had marked the screws to see if they were moving. The screws are not moving. I checked for vacuum leaks with propane but found none. It will be running perfect then suddenly the idle will change dropping around 150 to 200 rpm but will still run good off idle. Checking the sync the banks will be out considerably. Adjust the sync and the motor will come back to 1040 and idle perfect. A riding buddy suggested a sticking slide. Sounds reasonable. Any ideas would be greatly appreciated.

Tim



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rjlv25
Posts: 113
Joined: Mon Aug 06, 2012 9:04 pm
Location: Rochester, New York
Motorcycle: 2004 FXDLI Low Rider
1987 GL1200I Interstate
1982 GS1100L (SOLD)
1982 KZ1000LTD (SOLD)
1979 KZ750B4 (Traded)

Re: carb sync change mystery

Postby rjlv25 » Mon Sep 02, 2013 6:54 pm

Just a thought, but did you replace all the hoses and check for a vacuum leak? If it's not a fuel problem, it must be air.

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SteveB123
Posts: 842
Joined: Thu Apr 05, 2012 9:29 am
Location: Winchester, Ontario, Canada
Motorcycle: 1982 1100I, 60A Poorboy, MSD coil

Re: carb sync change mystery

Postby SteveB123 » Mon Sep 02, 2013 7:44 pm

If the carbs aren't moving them something else is changing the breathing.

Valve adjustment?
Current:82 GL1100 Interstate, 60 Amp Poorboy, MSD coil
Previous: 93 GSX1100F Katana
82 GL500 Silverwing

jtimgrant
Posts: 77
Joined: Sat May 25, 2013 7:24 am
Location: Greensboro NC.
Motorcycle: 1987 GL1200 Aspencade

Re: carb sync change mystery

Postby jtimgrant » Mon Sep 02, 2013 9:25 pm

I changed the hoses and pulled a vacuum at the #4 cyl. vacuum port on the vacuum hoses leading to the slow air cuttoff and air injection system. No leaks. I'm watching the sync closely. Right now I've noticed only a small change in the idle going up a few rpms. The movement of the rpm's has in the past been the indication that the sync is changing. The valves are hydraulic so they should be ok unless they are sticking or have carbon buildup. I've only put 3300 miles on it since getting it and it had set up for 5 years. I'm hoping riding it some will solve some of this.

Thanks for for replying!

Tim

jtimgrant
Posts: 77
Joined: Sat May 25, 2013 7:24 am
Location: Greensboro NC.
Motorcycle: 1987 GL1200 Aspencade

Re: carb sync change mystery SOLVED

Postby jtimgrant » Mon Sep 09, 2013 9:27 pm

Found the problem - I should have checked before posting. The nylon bushings in the right side linkage are worn allowing enough movement to change the sync. Now to find a source for these things.

Tim




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