GS1100G Power flat over 6000rpm, 85mph in 5th

[Buffalo Bill]

I have a slow time passing pilgrims because my power is flat over 6000rpm, or 85mph in 5th, is this an EPA mandate for 1982 bikes? Can I tune the top end for more passing power? This bike is all stock OEM as far as I can tell. I would like to keep it that way. Let me know.

[tkent02]

Should run fine at any RPM, pulling hard to way over 100 mph easily. That is a torque monster machine. Pilgrims should disappear from your mirror with a quick twist of the wrist. Some CV carbed bikes are very lean from the factory and are very susceptible to any air leaks. Look for air leaks around the airbox. You can tweak the jetting a hair richer like going to one size bigger main jets and raise the jet needles a bit, tweak the screws a tad richer. There should be jet kits available for that model. Have you checked everything else like ignition timing and spark advance?

[Nessism]

There is no simple tricks to get more power, without modifying the bike. Some people install a header, pod filters, and jet kit to get more top end power (often times at a loss of low and midrange power). Only simple thing to do to your bike is to shim the needles a little to richen up the midrange - many people notice an improvement in driveability, but no significant power increase.

[Dogma]

I have a slow time passing pilgrims because my power is flat over 6000rpm, or 85mph in 5th, is this an EPA mandate for 1982 bikes? Can I tune the top end for more passing power? This bike is all stock OEM as far as I can tell. I would like to keep it that way. Let me know.

I see this is your first post to the forum. Welcome aboard.

You should have fistfuls of power over 6k. The only EPA silliness I've heard of so far on these bikes is the caps over the pilot screws. If everything is stock, re-jetting isn't supposed to be necessary. Post some pics and we'll tell you if it's stock...

What can you tell us about the state of maintenance? There are some standard issues that usually need to be settled to get the real experts around here started. (I'm not one of them yet, but you learn fast around here)
Valve clearances correct?
Carb boots and o-rings known to be good?
Air box fully sealed?
Carbs clean? Cleaned how?
Float levels correct?
Petcock working and flowing correctly?
What is the condition of the spark?

[tkent02]

There is no simple tricks to get more power, without modifying the bike.

Getting it running correctly would be a good start. If it's done at 6,000 there is a problem.

[Buffalo Bill]

More info: GS1100G ('82) power flat over 6000

Air box, filter and carbs are all stock, and as they appear in the manual. Carbs were professionaly cleaned, but not syncronized on bike. Spark advance is not adjustible from 1982 and forward. No sign of cam wear, they look and guage real good. Petcock is new, plugs look normal.
Below 6000RPM motor has all the power I expect, but not above 6000RPM. At 60MPH in 5th, there is the normal power surge as I open the throttles followed by hesitation and only a slow climb in speed. I think this indicates not enough gas.
I'm new to bikes, but my background is sports cars. You boomers remember how the factories dropped horsepower in their cars from the mid 70s thru the mid 80s. The '69 Corvette 350 with 350HP, dropped to only 180HP in '77, and only 200HP for '82. Speedometers read only up to 85mph, likewise the Speedometer on this bike.
My theory is: because the power plateau is at 85MPH, the carbs were leaned out for WOT by the factory.
Do you guys think I can cure this problem by enriching the WOT mixture?
Thanks

[TheCafeKid]

Its worth a shot, but before you do that, try getting the carbs synced on the bike. You may be suprised what a difference that makes. Now, when it starts to have problems, is it breaking up? or just bogging? I have a little bit of "hesitation" on my bike, more like a flat spot, right around 3500-4000RPM, where it seems, if you wack the throttle open it takes a second (if that) for it to catch up, then suddenly there is a surge. I am inclinded to think, based on my plug readings as well, that i may actually be a little bit RICH, rather than lean, on the adjustment...

There is a WOT trick i read on here, tho ive never tried it. I think it was something like, crack the throttle to WOT, then pull the choke, if it surges, youre lean, or something like that...

[Nessism]

Cafe, that little flat spot very well could be the needle. Raise it up by .050" or so and see if it goes away - worked wonders on my 850.

Regarding Bill's bike, sounds like something is wrong with it. An 1100 should pratcially yank your arms out of their sockets when the bike gets to 6000 rpm. Sounds like the bike is not running on all cylinders or something basic. Carb sync will not cause a problem as described.

[Grandpa]

This situation you describe, losing power at a certain number of rpm's, should not happen to a GS1100G. I have a GS1100GK, 1984, same engine, and the power keeps on coming well past 85 mph.

A good state of tune is absolutely necessary for the performance the 1100G was designed to put out. Valves, carbs, plugs -- these are the ones to check out first.

My GK with 130,000 miles pulls like a dream throughout the rpm range. No hesitation, no flat spot, no missing, nothing unexpected. Just smooth, predictable power delivery.

[tkent02]

I'm new to bikes, but my background is sports cars. You boomers remember how the factories dropped horsepower in their cars from the mid 70s thru the mid 80s. The '69 Corvette 350 with 350HP, dropped to only 180HP in '77, and only 200HP for '82. Speedometers read only up to 85mph, likewise the Speedometer on this bike.
My theory is: because the power plateau is at 85MPH, the carbs were leaned out for WOT by the factory.

Suzuki did go as lean as they could from the factory to help pass emissions standards, gas is different now, your engine is different now, lots have changed and that super lean factory setting may not be working any more. Some bikes were leaner than others it seems, some still run well enough with the original settings, some don't. Raising the jet needle and using one size bigger main jets would fix this if it is indeed the problem

Before changing anything are the fuel levels in the float bowls correct?

Is every other engine adjustment adjusted correctly?

Is this problem at wide open throttle only, or smaller throttle openings as well?


Also, a clogged exhaust can cause this same symptom, I bought a bike once with a huge ball of steel wool stuffed into the collector of the 4-1 pipe for some reason, it had no power at all except at low RPM. Maybe you have some partial obstruction, dead animals, pack rat nest, cocoons, could be anything.

And, what do your spark plugs look like?
Run it in the dead RPM zone a little while and do a plug chop.

[Buffalo Bill]

Rode it 60 miles this morning.

This lack of power is only at WOT. When I accelerate, I shift on the torque/power peak at 5000. If I open the throttle slowly, the power gain is smooth. If I open the throttle quickly, there's a little stumble, like the gas flow can't keep up with the engines need. At 6000RPM the throttle is almost wide open, opened slowly or not, only slow acceleration.
The carbs were pro cleaned and set. I believe the floats were set correctly.

[tkent02]

The carbs were pro cleaned and set. I believe the floats were set correctly.

This would be the first thing I would check.
Pros suck unless it's their own bike.
Don't take enough time to do anything right, just do enough to get paid. Anymore a newly trained pro probably doesn't even know how carburetors work.
And most don't give a hoot about anything old.

[catbed]

torque/power peak at 5000? peak power is at 9000 and peak to is something like 7500 for my bike.

[paco13]

Don't forget the gas cap vent. This will cause this problem. try running bike with the cap popped loose or off, just not with a full tank so it doesn't splash.
Then check all the other stuff mentioned. Def. sounds like fuel starvation or sucking alot of extra air somewhere.

[Clone]

6000rpm your throttle should not be close to wide open. You should be a half or less. I would suspect a vacuum leak not pulling the slides up or the slides not moving freely in the carbs.