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Hello everyone! I got my GL1500 (1997) all back together today and all is well except, there's a backfire under a load or when I let off the throttle, and it feels like it is hesitating a bit (not as strong as usual). The history is that I bought this bike about a year and a half ago and proceeded to get pretty deep into it. The rear master cylinder for the rear brake had to be rebuilt, so I did that. I also put new timing belts in, new plugs, new air filter, new lights, brake pads front and rear, and some other minor parts (fuel filter). I had to take the collector box off to do the master cylinder, so that meant taking the right hand side exhaust manifold off, so new crush gaskets when I reinstalled that.

I started it after I put the new timing belts on, and it ran just fine. But, today, after I put everything back together, it started right up, but there was an obvious backfire, and I can hear it in the carb too, just not as often. I took it for a ride too, about 5 miles, and the backfire remained. I can rev it and hold it smooth but as soon as I let off the throttle I get pop pop pop. And when I'm loading it up, the motor/carb seems to hesitate/stutter slightly. The fuel in this is probably going on close to 2 years old, but I did add some stabil. I'm thinking I need to start over and check timing belts, but I followed the guidelines step by step and the timing marks were on point.

Before I get into starting over with the timing belts, is there anything more "low hanging fruit" that you'd look into? I have a gut feeling that I did the timing without changing a thing, but I need to get going on this and thats my theory right now.

Thanks you all!

Matthew
 

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Since sparkplugs were changed too, I'd suspect a couple sparkplug wires got crossed.....
 

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Its kind of hard to cross the plug wires on a 1500 wing.
 
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Does it backfire out the exhaust or carbs? My first thought is vacuum leak. or lean fuel mixture. Try it down the highway or up a steep hill and add choke. Does that help wen you add choke? :).
 

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Discussion Starter #6
Does it backfire out the exhaust or carbs? My first thought is vacuum leak. or lean fuel mixture. Try it down the highway or up a steep hill and add choke. Does that help wen you add choke? :).
I'll try that. It is out of the exhaust but I can hear/feel the carbs acting up too (but not nearly as much as the exhaust, the exhaust I can almost 'make' backfire, but not the carbs). I did not do anything to the carbs and it was running great prior to my taking it apart and working on it.

I'll try the choke trick to see how that changes things and report back. I SOOOOO appreciate the help because the last thing I want to do is get under there and go back through taking parts off and look at that timing situation. I wish I had taken a picture of it prior to me putting it back together but those pulley marks were looking perfect, and nothing moved between belt changes.
 

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I'll try that. It is out of the exhaust but I can hear/feel the carbs acting up too (but not nearly as much as the exhaust, the exhaust I can almost 'make' backfire, but not the carbs). I did not do anything to the carbs and it was running great prior to my taking it apart and working on it.

I'll try the choke trick to see how that changes things and report back. I SOOOOO appreciate the help because the last thing I want to do is get under there and go back through taking parts off and look at that timing situation. I wish I had taken a picture of it prior to me putting it back together but those pulley marks were looking perfect, and nothing moved between belt changes.
I had a very similar problem a while back. It started and ran OK but as soon as you put a load on the engine it sounded like someone was shooting at me. Turned out there was a vacuum leak between the carbs and rubber isolators. The screws were tight but the isolators were not tight to the carbs/intake.The clamps have stops built in. No matter how tight the screw is the isolators were not sealing . The clamps were just tight to the stops.

I took my clamps apart and ground the stops shorter. Put the carbs back on and tightened the clamps. The isolators seemed to seal and the problem was gone.:)
 

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Discussion Starter #8
I had a very similar problem a while back. It started and ran OK but as soon as you put a load on the engine it sounded like someone was shooting at me. Turned out there was a vacuum leak between the carbs and rubber isolators. The screws were tight but the isolators were not tight to the carbs/intake.The clamps have stops built in. No matter how tight the screw is the isolators were not sealing . The clamps were just tight to the stops.

I took my clamps apart and ground the stops shorter. Put the carbs back on and tightened the clamps. The isolators seemed to seal and the problem was gone.:)
Thanks so much. I'll start looking around for something along those lines. I'm hopeful. There's a chance that I got something loose when I was changing out the air filter and fuel filter down in there. So much tightly packed together on these bikes.
 

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You need to get rid of that 2 year old gas, and put fresh gas in. Add 4 ounces of Seafoam, and take it on a nice long road trip.
gumbyred
 

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Lean fuel mixtures and leaking secondary ignition (poor connection between plug and wire, poor insulation/cracked plug wires etc) are hw 2 most common causes or loud backfire out the exhaust. Are you sure you pushed the plug wires home. The connection between the wire and resistor plug end?
 

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Discussion Starter #12
Lean fuel mixtures and leaking secondary ignition (poor connection between plug and wire, poor insulation/cracked plug wires etc) are hw 2 most common causes or loud backfire out the exhaust. Are you sure you pushed the plug wires home. The connection between the wire and resistor plug end?
Hello everyone. Thanks so much for the ideas. I started with the basics, and began checking those before going back to look at timing. Turns out, I had crossed two wires on the lh side, and once I correctly routed those, bam, started up like it could not wait. I can't make it backfire now if I want to. It was a great break for me, because I haven't the time to get back on the creeper and wedge my head between the front of the bike and the back of the tire! Thanks so much everyone, truly made my week.

Matthew
 

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Discussion Starter #14
Thanks for coming back and telling us what the problem turned out to be. It may really help the next guy with a backfire issue.
Of course, and I agree. I feel a sense of loss when I am problem solving using the forum and I read a thread and I'm like "yes! this guy has my problem, I'll read on to see how he fixed it," only to read on and see he got some suggestions but then.....silence.

Its good karma to close the deal.

M
 

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a silent ending to any troubleshooting thread is an abuse of the forum members generosity to help.
the OP should always come back and state how the situation ended up...
even if all he can do is throw it in the trash.
 

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Hello everyone! I got my GL1500 (1997) all back together today and all is well except, there's a backfire under a load or when I let off the throttle, and it feels like it is hesitating a bit (not as strong as usual). The history is that I bought this bike about a year and a half ago and proceeded to get pretty deep into it. The rear master cylinder for the rear brake had to be rebuilt, so I did that. I also put new timing belts in, new plugs, new air filter, new lights, brake pads front and rear, and some other minor parts (fuel filter). I had to take the collector box off to do the master cylinder, so that meant taking the right hand side exhaust manifold off, so new crush gaskets when I reinstalled that.

I started it after I put the new timing belts on, and it ran just fine. But, today, after I put everything back together, it started right up, but there was an obvious backfire, and I can hear it in the carb too, just not as often. I took it for a ride too, about 5 miles, and the backfire remained. I can rev it and hold it smooth but as soon as I let off the throttle I get pop pop pop. And when I'm loading it up, the motor/carb seems to hesitate/stutter slightly. The fuel in this is probably going on close to 2 years old, but I did add some stabil. I'm thinking I need to start over and check timing belts, but I followed the guidelines step by step and the timing marks were on point.

Before I get into starting over with the timing belts, is there anything more "low hanging fruit" that you'd look into? I have a gut feeling that I did the timing without changing a thing, but I need to get going on this and thats my theory right now.

Thanks you all!

Matthew
I suspect that it is sucking air either through the collector box or the exhaust gaskets.
 

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I suspect that it is sucking air either through the collector box or the exhaust gaskets.
I suspect if you had read the thread you would have seen the problem was already solved.
 
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