Backfire thru muffler


Information and questions on GL1000 Goldwings (1975-1979)
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BaronBigDog
Posts: 12
Joined: Sat Aug 10, 2013 10:46 pm
Location: Magnet Cove, AR
Motorcycle: 1975 GL1000

Backfire thru muffler

Postby BaronBigDog » Mon Dec 01, 2014 8:38 pm



Coming home from a very short ride yesterday my 75 GL1000 started backfiring through the left muffler. I have a split system, no crossover. It pops pretty loud. (Sounds like an old Harley with the timing too far up) If I hold #2 carb closed and open the throttle on the remainder and it does not backfire. As soon as I let off the linkage and it opens up it starts backfiring. My carbs are relatively fresh from a professional rebuild--Old School Carbs--and until yesterday were perfect. Everything is virtually new on the bike in the realm of spark and fuel supply. Any suggestions before I start tearing into it?

I looked at the troubleshooting guide in the service manual and it suggest timing, but I think that if the timing was off it would affect both 2 and 4. It appears to be 2 only, but this may be a misdiagnosis.

Just to be certain that you know the following are new.

Plugs
Wires
Coils
Plug caps
Electronic ignition
Rebuilt carbs
Electric fuel pump
Running no ethanol regular gas
A total of 226 miles on the above.
A whole lot of other new stuff that would have no affect on this problem.



User avatar
Aussie81Interstate
Posts: 683
Joined: Thu Nov 27, 2014 2:34 am
Location: Penrith Australia
Motorcycle: 1982 CX500 Turbo (restoration project)
1981 GL1100 Interstate (sold)
1988 GL1500

Re: Backfire thru muffler

Postby Aussie81Interstate » Mon Dec 01, 2014 10:33 pm

make sure #2 carb is receiving fuel - undo the drain screw to confirm there is fuel in there (motor off - on the centrestand - fuel tap off) - catch the contents of the bowl and compare the level to the other carb bowls - should be the same. also make sure there are no vacuum leaks around the carb inlets

User avatar
RBGERSON
Posts: 2625
Joined: Tue Mar 09, 2010 7:57 am
Location: SCOTTSDALE, AZ
Motorcycle: 98 SE GL 1500
had every year from 75 to 83

Re: Backfire thru muffler

Postby RBGERSON » Tue Dec 02, 2014 9:08 am

Gl's are a wasted spark system sounds like extra fuel in the cylinder being ignited at the wrong time..IE when exhaust valve is open.
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB


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