1977 GS550 Running Hot

[Guest]

Hey all,

I'll try to be as specific as I can with my setup. Carbs just cleaned, all o-rings and gaskets replaced, new o-rings for the carb boots which are still healthy, added pod filters and Emgo shorty mufflers. Subsequently upped the main jets from stock 80 to 100's and raised the needle one or two notches (I did it a while ago and need to double check). All valve clearances are in spec, new points installed, new plugs, new battery. Prior to all of this the bike was stock, and not running well. It was a classic hard to start / took forever to warm up and idle scenario. After six months of not running, I bench synced the carbs, reinstalled and it started with the new setup instantly and idles beautifully. However I notice the first bend of the pipes coming out of the engine are slightly blueing shortly after the bike idles for a few minutes. I think the engine is running hot and I'm looking for some ideas as to what I can do to help fix that.

I have read on here that similar issues people have had can be caused by a few different things. One, the mixture could be too lean. This seems logical for my bike as the new filters would be letting in a huge amount of air more than the stocker setup. Like I said, I upped my main jets, but I'm wondering if I need to go even bigger. I tried the max idle method of adjusting the pilot air screws to try to richen the mixture as well, but I'm not sure if that did much. Also I'm not sure if I raised the needles (clips) enough when I rejetted. I'm aware that the carbs need further tuning, but I'm not sure if those fine tunings will help solve this problem too.

Any other ideas of what could be causing this? Note: Pod/pipe critics need not apply.

Thanks!

[gsrick]

Lean condition is more than likely the only thing that turns the pipes blue. How many sizes did you go up? I think most pods require at least a jump of two sizes maybe three. Clean the blue off and see if it comes back.

[mmattockx]

Any other ideas of what could be causing this? Note: Pod/pipe critics need not apply.

No pod/pipe critic here, I have APE pods and a Kerker 4-1 on my 1100E and it runs great. Do I know what's causing this? I would say it is not being jetted correctly after a major change to the engine airflow. Just randomly tweaking things won't solve your issues, you need to properly work through the carb ranges and set things according to what the engine tells you it wants.

Put some tape on your throttle housing and mark the throttle opening in 1/8 turn intervals. Then go for a test ride. The pilots control idle-~1/8 throttle, then needles ~1/8-3/8 throttle, then the main jet after that. Go out on a back road where there is little traffic and try this: get into 3rd or 4th gear, let it slow down to 2500-3000rpm or so and then open the throttle to each different range and let the bike accelerate at a steady throttle setting. Once it is pulling steady pull the choke/enrichener and notice what happens. If you are lean it will clean out and pull harder. If you are about right it will bog slightly. If you are rich it will bog badly.

Once you have done some road testing and know what each carb circuit range is doing you will know what you have to do to the jets and needle to sort it out.


Mark

[hannibal]

Put some tape on your throttle housing and mark the throttle opening in 1/8 turn intervals. Then go for a test ride. The pilots control idle-~1/8 throttle, then needles ~1/8-3/8 throttle, then the main jet after that. Go out on a back road where there is little traffic and try this: get into 3rd or 4th gear, let it slow down to 2500-3000rpm or so and then open the throttle to each different range and let the bike accelerate at a steady throttle setting. Once it is pulling steady pull the choke/enrichener and notice what happens. If you are lean it will clean out and pull harder. If you are about right it will bog slightly. If you are rich it will bog badly.

Once you have done some road testing and know what each carb circuit range is doing you will know what you have to do to the jets and needle to sort it out.


Mark

That's some great advice right there. Never thought of that.

[HogsRear]

No pod/pipe critic here, I have APE pods and a Kerker 4-1 on my 1100E and it runs great. Do I know what's causing this? I would say it is not being jetted correctly after a major change to the engine airflow. Just randomly tweaking things won't solve your issues, you need to properly work through the carb ranges and set things according to what the engine tells you it wants.

Put some tape on your throttle housing and mark the throttle opening in 1/8 turn intervals. Then go for a test ride. The pilots control idle-~1/8 throttle, then needles ~1/8-3/8 throttle, then the main jet after that. Go out on a back road where there is little traffic and try this: get into 3rd or 4th gear, let it slow down to 2500-3000rpm or so and then open the throttle to each different range and let the bike accelerate at a steady throttle setting. Once it is pulling steady pull the choke/enrichener and notice what happens. If you are lean it will clean out and pull harder. If you are about right it will bog slightly. If you are rich it will bog badly.

Once you have done some road testing and know what each carb circuit range is doing you will know what you have to do to the jets and needle to sort it out.


Mark

Awesome, thank you for that. I'm still a few steps away from having the bike be rideable, but as soon as it is I will do this test. Thanks!