1980 GS1000G wont rev out past 4k

[charlie27]

hi,

working on a bike not on the road since '96. so far I have:

1) adjusted valves - good now
2) did compression check very good on 3 cylinders and a bit lower on #3 but within limits
3) total carb rebuild - all new orings, full disassembly, ultrasonic clean with simple green - look good
4) careful reassm - adjusted float level, bench sync, 3.5 turns out on mixture screw
5) new plugs - gapped to spec
6) the bike had no air filter when I got it - got the filter and the metal frame. The air box seems to be missing an intake snorkel - large hole bottom back of the air box - very suspicious about this and how it effects running - should I tape over part of it to compensate?
7) got it started, warmed up and then adjusted idle. Dead smooth at 1100rpm, no bog on initial throttle - just wont rev past 4500
8) running off small fuel tank used for tuning

any idea on how the missing snorkel will effect? I have research bad ignitor can cause the bike not to rev. Before I shot gun it looking for a methodical approach to sort.

thanks

[Guest]

hi,

working on a bike not on the road since '96. so far I have:

1) adjusted valves - good now
2) did compression check very good on 3 cylinders and a bit lower on #3 but within limits
3) total carb rebuild - all new orings, full disassembly, ultrasonic clean with simple green - look good
4) careful reassm - adjusted float level, bench sync, 3.5 turns out on mixture screw
5) new plugs - gapped to spec
6) the bike had no air filter when I got it - got the filter and the metal frame. The air box seems to be missing an intake snorkel - large hole bottom back of the air box - very suspicious about this and how it effects running - should I tape over part of it to compensate?
7) got it started, warmed up and then adjusted idle. Dead smooth at 1100rpm, no bog on initial throttle - just wont rev past 4500
8) running off small fuel tank used for tuning

any idea on how the missing snorkel will effect? I have research bad ignitor can cause the bike not to rev. Before I shot gun it looking for a methodical approach to sort.

thanks

Not sure, but thats the same symptom you'd get putting on pods and not rejetting the mains. Not enough fuel with the amount of air that it is getting. I'd try taping off that hole and see what happens.

[Dharma-man]

hi,

working on a bike not on the road since '96. so far I have:

1) adjusted valves - good now
2) did compression check very good on 3 cylinders and a bit lower on #3 but within limits
3) total carb rebuild - all new orings, full disassembly, ultrasonic clean with simple green - look good
4) careful reassm - adjusted float level, bench sync, 3.5 turns out on mixture screw
5) new plugs - gapped to spec
6) the bike had no air filter when I got it - got the filter and the metal frame. The air box seems to be missing an intake snorkel - large hole bottom back of the air box - very suspicious about this and how it effects running - should I tape over part of it to compensate?
7) got it started, warmed up and then adjusted idle. Dead smooth at 1100rpm, no bog on initial throttle - just wont rev past 4500
8) running off small fuel tank used for tuning

any idea on how the missing snorkel will effect? I have research bad ignitor can cause the bike not to rev. Before I shot gun it looking for a methodical approach to sort.

thanks

Interesting... I'd be very curious to hear how this played out.

[trippivot]

inspect your timing advance unit- if it is frozen in place you will have this exact problem. it should move freely and snap back.

verify that your vacuum slides are lifting fully .

after that recheck your carb work

[GregT]

inspect your timing advance unit- if it is frozen in place you will have this exact problem. it should move freely and snap back.

verify that your vacuum slides are lifting fully .

after that recheck your carb work

And verify the jet sizes are stock. If the filter was missing, it could well have been rejetted to suit.

[chuck hahn]

3 1/2 out on the mixture screws seems a tad excessive based on forum members general experiences. Timing should be checked when your investigating the advancer. The hole for the missing snorkel isn't the issue..it just missing the rubber. Try adding a little choke when it limits out. If it gets better your running lean. If it gets worse or no change its rich.

See the CV tuning sticky at the top of the carb section.

[headsbikesmopars]

What Trippivot said, My sons '81 GS750EX would not pull past 4,000 so I pulled the carb bank to find #2 and #3 slide diaphrams were leaking so they were not working. All lower speeds bike ran fine but with weak pull at full throttle. The diaphrams had wrinkles in it and would not hold vacuum . After reinstalling those slides properly it will pull to redline very strongly ! Just something to check out .

Terry

[salty_monk]

Also do the test on the CDI in the manual (the one where you connect up a 1.5v battery).
Years ago I had similar symptoms on an 80 1000G that I chased with carb settings for a 2-3 months before working out that it was in the CDI. Mine was limited a little higher at about 6k from memory.

[Lorenzo]

I do feel coils should deserve a more prominent position, in the great fault finding scheme of things.