misfiring over 6000 rpm

[Guest]

gentlemen, I purchased a 1982 gs1100e with 7000 miles that sat unused since 1986? or so. I have come to the end of my restoration which included all brake hydraulic components,gas tank de rust and seal, new oem fuel petcock, carb overhaul following the excellent guidelines on this website with new o rings and brass. I now have a bike that starts, idles and runs perfectly up to 6000 rpm at which point it misfires as if there is a rev limiter...on occasion if I hold the throttle wide open while its misfiring it will clear momentarily and go back to breaking up. It has been difficult to determine if the cause is fuel or spark but heres a list of areas I've covered. First off the bike is all stock, no mods. spark plugs are white and chalky, increased main jet from factory 110 to 112, no change. ran with air filter out, no change. valve lash set to spec, ohmed out coils and found them out of spec when hot..changed coils to dyna. replaced igniter with used one from ebay, no change. checked fuel flow with petcock on prime compared to run and flow is good. Checked function of timing advance and found it to be free. I am now wondering if the rubber diaphrams on the carb slides may be the problem (rubber circa 1982) but if i blow into the air duct the slides raise..Any advice from this forum would be greatly appreciated.
Thanks, Joe

 

[Grimly]

I wonder if it's the advance springs got weak and allowing too much advance >6K. How did you check it? With a decent timing light?
I suspect the same may be happening in mine.

 

[Guest]

I just turned it with a wrench and felt it work up against the spring. It works freely with no binding. Didn't use a timing light.

 

[93Bandit]

I think you should check timing advance with a timing light. That may reveal what's going on.

 

[Rijko]

Does the igniter get proper 12V and ground ?
If not, even good ones don't function well.

No head work done ?
I have seen similar with a GS1000 that had some of the valve springs mounted upside down.

 

[salty_monk]

I had something similar on a 80 GS1000. It was the ignitor. Up to 6k you couldn't have told anything was wrong. I thought all the 82 models had the advance inside the ignitor not a mechanical one.... Might want to make sure you have a matching set. Maybe someone replaced it and added a mechanical and then someone else put an electric advance model on it...

If you do have a mechanical advance a Dyna S is the way forwards

 

[Rijko]

Just for fun measure power to the green/yellow wire of the starter relais. Not familiar with the gs1100e but that wire should get its power from the rh handlebar switch just like the igniter.
If that green/yellow wire does not receive 12V chances are neither does the igniter.

 

[Guest]

Thanks for the feedback guys. I believe Suzuki went away from the mechanical advance in 83. The ebay ignighter has the same part numbers as the original. This bike is a 7000 mile and there is no evidence that the head has been off. The previous owner bought it New and supplied documentation of every service.

 

[Guest]

I will check for voltage at the ignighter. Are they a common component that fails?

 

[Rijko]

I will check for voltage at the ignighter. Are they a common component that fails?

Definitely. Usually due to corroded connectors, and over voltage after a R/R fail.
I worked on a GS450 with failed igniter recently and like Salty said - lower rpm it was fine, higher rpm it would run badly.

 

[salty_monk]

Yeah the components go bad at a board level. Likely a dry joint or capacitors or something. Unfortunately they are potted so you can't really work on them. If you have electronic advance you need the Dyna 2000 or I think some have used https://www.ignitech.cz/cz/

 

[chris]

I will check for voltage at the ignighter. Are they a common component that fails?

Hi , I would say that the gs1100 ignition is reliable. I kept mine all original since 1986 when I bought the bike. The only reason I bought a ignitech is for backup, new ignitors are really expensive. The problem could be carburators. The white and chalky plugs are not good. They should be light tan. Only on modern fuel injected bikes do I see white plugs. Old CV carbs can be difficult to clean to have them running great and the chemicals required almost impossible to get in some areas. Just remember a set of rs36 's still cost less than a day of shop fees and they are awesome . Saying that I would confirm your ignition in good shape before spending the money. You have a very nice bike, hopefully you can get it running the way it was meant to. It should scream past redline with ease.