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Posted

My bike has developed a popping noise in the left exhaust pipe at idle. Along with that my gas mileage is only about 30 MPG. Any thoughts or guesses?

 

Duane:bang head:

Posted

when the bike is warming up feel the cylinders, or of cool enough feel the exhaust pipes odds are something is cooler, indicating a cylinder not firing. raw gas is getting to the hot exhaust pipe and buring off there. Why is your problem to chase usually electrical or valve timming

 

Al

Posted

you could have a float that is sticking, or a bad spark plug when is the last time you put in new plugs. take the plugs out and see if you have one thats runing rich should be black colored and maybe wet with gas.

Orlin

Posted

Those pipes will warm up VERY quickly. Check when its cold just keep feeling the pipes touching them one at a time til they get too hot to touch and see if one is behind the others. You can still touch it after others are too hot to touch. That is guilty one!! Start with changing plug. Most of the time that will cure problem. Don't Burn Fingers!!

Posted
it could be an out of sync carb or a bad plug wire and cap? have you checked your diaphragms?

 

I had a shop do the carbs in January, the plugs and wires were changed then. BTW the bike did not run at all then, but ran great for about a month after I got it back. I haven't checked the diaphragms yet I guess I could have developed some holes since then. When the hesitation started I changed that plug again about 3 weeks ago.:depressed:

Posted
I had a shop do the carbs in January, the plugs and wires were changed then. BTW the bike did not run at all then, but ran great for about a month after I got it back. I haven't checked the diaphragms yet I guess I could have developed some holes since then. When the hesitation started I changed that plug again about 3 weeks ago.:depressed:

Did you try to adjust the idle mixture screw on that cylinder?

Posted

There's a small screw hidden way back in this hole, that is your air mixture screw. It might have a brass plug to keep you from playing with it, so you'll have to drill a small hole in the plug, then insert a screw to be able to remove it. Once you can get at it, then start the bike and turn the screw out a turn or two. If that helps your problem you can either leave it and be happy, or you can remove it and clean inside there with some carb cleaner. To remove the screw is tricky, turn it until it is free from the threads and then suck it out with a turkey baster or some such tool. There are 3 parts and you'll need them all for reassembly.

The screw, which has a very fine needle on the end, a spring seated on the screw and a rubber coated washer on top of the spring (sits between the spring and the engine). Be careful to find the washer and put it back in.

Once done cleaning, put the spring and the washer back on the needle valve (screw) and turn it back into place. DO NOT turn in tight, only very carefully until it comes to a stop, don't worry, if you are careful you'll feel the stop. Now turn it back out 2.5 turns and try the engine again. You may need to adjust the screw some what, first to get the cylinder to fire, and then to get it to run as best as possible. This is all done by ear and feel, so enjoy.

Posted
Did you try to adjust the idle mixture screw on that cylinder?

 

Today I messed with the idle mixture. I didn't remove it to clean but did get the popping to stop, but the cylinder is still cold at idle.:depressed: I also checked the diaphragm and it was good, no holes or tears. I am going to change the coil on that cylinder and check the rest of the diaphragms.:detective:

Posted
Today I messed with the idle mixture. I didn't remove it to clean but did get the popping to stop, but the cylinder is still cold at idle.:depressed: I also checked the diaphragm and it was good, no holes or tears. I am going to change the coil on that cylinder and check the rest of the diaphragms.:detective:

So now that you got the popping to stop, it's time to start the bike and then remove the plug wire to see if it make a difference in the running. You may have a bad plug, but I'm guessing that you have a partial plugged idle circuit and that you'll notice a difference when you remove the plug wire. I use a long handled needle nose pliers to remove the plug wire, otherwise I have a shocking experience.

Posted
So now that you got the popping to stop, it's time to start the bike and then remove the plug wire to see if it make a difference in the running. You may have a bad plug, but I'm guessing that you have a partial plugged idle circuit and that you'll notice a difference when you remove the plug wire. I use a long handled needle nose pliers to remove the plug wire, otherwise I have a shocking experience.

 

I removed the plug wire and didn't notice any change in RPM or idle smoothness. Took the plug out and it is firing. I will remove and clean the air mixture screw tomorrow.

Posted

The screw, which has a very fine needle on the end, a spring seated on the screw and a rubber coated washer on top of the spring (sits between the spring and the engine). Be careful to find the washer and put it back in.

Once done cleaning, put the spring and the washer back on the needle valve (screw) and turn it back into place. DO NOT turn in tight, only very carefully until it comes to a stop, don't worry, if you are careful you'll feel the stop. Now turn it back out 2.5 turns and try the engine again. You may need to adjust the screw some what, first to get the cylinder to fire, and then to get it to run as best as possible. This is all done by ear and feel, so enjoy.

 

I took the idle mixture screw today and cleaned it with no change. I took one from my parts bike and compared them. It looked like the one I was using was bent slightly when I compared the two. The one from the parts bike also had a metal washer between the spring and rubber washer. I cleaned this one and installed it. So far it seem to be working, the cylinder is firing and no noise. it's raining too much today to ride tomorrow should be better and I put it to the test. :fingers-crossed-emo

Posted

My guess would be a sticking or clogged float needle valve, dumping raw gas into the cylinder causing the plug to cold foul. Had the same issue on an 87 Venture. Ended up changing all the gas lines. The old ones were deteriorating from the inside, probably caused by ethanol.

  • 1 month later...
Posted

I haven't been able to ride for about a month (broken ankle) and finally got my bike home. The popping noise and cold cylinder have returned any other thoughts?:confused24:

Posted

have you tried a good dose of Sea Foam ?? Let it soak for a week or so.

Also, drain the carb bowls several times, with Sea Foam, in the fuel.

 

Also, I'm thinking maby the carb sync was not done correctly.

 

Check the Pull cable of the throttle, at left fwd carb. Is there Any Slack in the cable, before the Linkage starts to move. IF not, most likley the cables need to be re-adjusted, and you need to Re-Sync the Carbs. Do you have the Morgan Carb Tune tool ??

Posted
There's a small screw hidden way back in this hole, that is your air mixture screw. It might have a brass plug to keep you from playing with it, so you'll have to drill a small hole in the plug, then insert a screw to be able to remove it. Once you can get at it, then start the bike and turn the screw out a turn or two. If that helps your problem you can either leave it and be happy, or you can remove it and clean inside there with some carb cleaner. To remove the screw is tricky, turn it until it is free from the threads and then suck it out with a turkey baster or some such tool. There are 3 parts and you'll need them all for reassembly.

The screw, which has a very fine needle on the end, a spring seated on the screw and a rubber coated washer on top of the spring (sits between the spring and the engine). Be careful to find the washer and put it back in.

Once done cleaning, put the spring and the washer back on the needle valve (screw) and turn it back into place. DO NOT turn in tight, only very carefully until it comes to a stop, don't worry, if you are careful you'll feel the stop. Now turn it back out 2.5 turns and try the engine again. You may need to adjust the screw some what, first to get the cylinder to fire, and then to get it to run as best as possible. This is all done by ear and feel, so enjoy.

or a colortune

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