Backfiring with flame coming out of exhaust
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Kenstoy2
- Posts: 3
- Joined: Wed Jul 27, 2016 2:46 am
- Location: Keizer, Or
- Motorcycle: 1984 GL1200 Interstate
Backfiring with flame coming out of exhaust
Hi. I have a GL1200. I have flame coming out of the exhaust with a loud bang after starting. It idles okay. I had the carb's cleaned and still persists. When I give throttle to 3500 to 4000 rpm, and back off, it pop's and backfires. I would appreciate your conclusions.
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virgilmobile
- Posts: 9102
- 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: Backfiring with flame coming out of exhaust
Simply there's unburnt fuel in the exhaust that's being ignited.
Now why.???
Easy stuff first.Compression OK?Lots of spark?
Nice spark plugs?
From cold,idle for 6-7 seconds and shut down.Lightly tap each header.Are they all the same "warm" ?
Were the floats in the carbs set exactly right...to the mm. And do they actually shut off the fuel?
Have the slides been confirmed as moving up and down with the rpm?
Any vacuum lines left disconnected or bad?
Was the air cutoff valve checked and verified operational and not stuck open?
Oh so many possibilities.
Now why.???
Easy stuff first.Compression OK?Lots of spark?
Nice spark plugs?
From cold,idle for 6-7 seconds and shut down.Lightly tap each header.Are they all the same "warm" ?
Were the floats in the carbs set exactly right...to the mm. And do they actually shut off the fuel?
Have the slides been confirmed as moving up and down with the rpm?
Any vacuum lines left disconnected or bad?
Was the air cutoff valve checked and verified operational and not stuck open?
Oh so many possibilities.
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twocams
- Posts: 677
- Joined: Tue Sep 29, 2015 11:25 am
- Location: Grants Pass, Oregon
- Motorcycle: 1985 GL1200 Aspencade ( sold in Canada), 2003 K1200GT BMW, 1969 R69S BMW,92 R100 RT BMW
Sold : 84 V65 Magna, 82 Moto Guzzi, XS 1100 Yamaha,84 Wing Int., 80 650 Special, Only new bike 82 XV750 Virago (Guam),Honda 250,84 R100RT BMW,87 K100 LT BMW,93 K1100 LT BMW, 91 535 Virago, Honda 50
Re: Backfiring with flame coming out of exhaust
Flame thrower....kool. 
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virgilmobile
- Posts: 9102
- 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: Backfiring with flame coming out of exhaust
Yea but only on startup.
I think your wanting one on demand...
Now that would be kool.
Don't get me started engineering this.
