[jefram]

imported post

My '83 GL1100I has a stumble that starts around 5500 rpm and continues till redline. The last things I did to the bike before this startedwere new air cut offs for all four carbs and shimming the needles.Usuallywhen the bike is still cold it will pull to redline with no stumble but once it warms up it runs greatup to70 mphthen starts the stumble and will overheat above 75 mph. I'm going to do a plug chop on the way home today and see if that reveals anything. Does anyone know what the stock jet & needle sizes are and what rpm range is covered by each jet?

 

[jefram]

imported post

twisty wrote:

It probably wouldn't hurt to check your ignition advance as that can cause a lack of power & late ign timing can easily cause engine overheating. The only thing is; late ignition usually doesn't cause an engine to not rev up (a little lethargic maybe but it should still rev up).

After searching the archives and finding the same type of symptoms in threads dealing with pulse coils and generators I'm pretty sure it is ignition related. I checked the vacuum advance and found that itwill pull but not holding a vacuum. It will rev all the way to redline it just starts breaking up at 5500 and then starts with the detonation. It did not do this before I pulled the carbs to replace the cut offs so I just figured it was related to that. Thanks for the help!