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The idle on my '80 GS1100 hunts between 1000 - 1500 rpm.
What I did: I pulled my carbs because I was having a fuel supply challenge. A PO had spliced the fuel line, and he used a soft tube which now easily kinks at the splice. So naturally I figure the fuel supply is getting choked off. I replaced the fuel and vacuum lines with a spiffy looking TYGON tubing rated for gasoline & temps up to 140 degrees. The lines are yellow & transparent. More on this later.
While the carbs were off I replaced all the phillips head screws on the diaphram covers and float bowls with SS allen head bolts. I replaced them one at a time, and did not replace any gaskets. Risky, I know.
After re-installing the carbs and doing a sync, I have this challenge at idle. The rpm goes up...the rpm goes down... I know you will say this is a classic sign of an air leak. I find none using carb cleaner to spray all over the boots. There seems to be no reaction to the spray. The idle still hunts the same way.
I now notice there is fuel in the vacuum line from the petcock (not a lot). Remember it is transparent. I'm thinking there should be no fuel in this line. But because the line is traditionally black, maybe I just never would have noticed it. There is also a large air bubble in the fuel supply line. I can see both these lines react to the increase in RPM when I pull the throttle.
Air in the fuel line would be a problem IMO. Fuel in the vacuum line would be a problem IMO. Sounds to me like I have a problem in my petcock. Maybe that was my problem originally. My petcock has no valve on it. I cannot select prime (that would help get rid of the air bubble) or reserve. I've never seen a petcock without a manual valve before.
Any advice would be appreciated. I'm planning to take this bike on a long road trip. The last run before winter. I hope I can nail this down quickly.
What I did: I pulled my carbs because I was having a fuel supply challenge. A PO had spliced the fuel line, and he used a soft tube which now easily kinks at the splice. So naturally I figure the fuel supply is getting choked off. I replaced the fuel and vacuum lines with a spiffy looking TYGON tubing rated for gasoline & temps up to 140 degrees. The lines are yellow & transparent. More on this later.
While the carbs were off I replaced all the phillips head screws on the diaphram covers and float bowls with SS allen head bolts. I replaced them one at a time, and did not replace any gaskets. Risky, I know.
After re-installing the carbs and doing a sync, I have this challenge at idle. The rpm goes up...the rpm goes down... I know you will say this is a classic sign of an air leak. I find none using carb cleaner to spray all over the boots. There seems to be no reaction to the spray. The idle still hunts the same way.
I now notice there is fuel in the vacuum line from the petcock (not a lot). Remember it is transparent. I'm thinking there should be no fuel in this line. But because the line is traditionally black, maybe I just never would have noticed it. There is also a large air bubble in the fuel supply line. I can see both these lines react to the increase in RPM when I pull the throttle.
Air in the fuel line would be a problem IMO. Fuel in the vacuum line would be a problem IMO. Sounds to me like I have a problem in my petcock. Maybe that was my problem originally. My petcock has no valve on it. I cannot select prime (that would help get rid of the air bubble) or reserve. I've never seen a petcock without a manual valve before.
Any advice would be appreciated. I'm planning to take this bike on a long road trip. The last run before winter. I hope I can nail this down quickly.
I was thinking if you pinch off the vacuum line and see if there is a difference you may be able to see if it's the vacuum line or not. I'm thinking there has to be a minute or two of idleing time worth of gas in the float bowls. Just a thought. :roll:
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