High cruise rpm, what do I have?

[Guest]

Hi guys,
I'm a recently new member to GSR, though I've been lurking around the forum for a while now. This is my first post so please forgive any early gaffes regarding forum etiquette.

Over the winter, I purchased a new-to-me 1982 GS1100G. With the help of the forum I was able to get the bike well-sorted, with new o-rings from cycleorings.com, new clutch springs, fibers, and lever from partsoutlaw.com, valve adjustment, fork rebuild, carb adj. & synch., etc. The bike runs great and starts instantly, hot or cold, and pulls hard throughout. There is a wealth of knowledge here, and it was instrumental to the resurrection of this bike. Thanks to all involved.

The question I have concerns gearing on this machine. At 70 mph (verified by GPS speedo), this particular bike is turning an indicated ~5100 rpm. The build date on the headstock is 2/82. The engine code on the case is U701-108xxx which, if I am correct, should mean this is an 1100. According to the gear chart I found here, my bike should be turning almost 1k rpm less at speed.

(I tried to place the chart here, but couldn't post the .jpeg. Sorry.)

There is NO clutch slippage. The bike will easily get air on a 1-2 shift, and all the secondary and final drive components are in great shape. I am running a Metzler Sportec in 130/90-17. According to everything I have read here, there is no combination that will allow this high cruise rpm on an 1100.

Concerning advertised top speed: Did Suzuki determine top speed as a calculation of engine rpm or by actual performance? If you do the math, my bike is running approx. 123 mph @ 9000 rpm. This bike will easily pull past this. With the lower listed cruise rpm, this works out to 147 mph. Quit a difference.

I have searched quite thoroughly and not been able to find this particular issue anywhere on the forum. As stated previously, the bike runs great and doesn't seem to mind the revs, but I do a fair amount of highway driving and think it may benefit from a lower cruise rpm. Did Suzuki ever throw together any oddballs out of leftover parts? I know it's not uncommon for auto manufacturers to do so during model year changes, but... ?

Can anyone help identify what I have? Thanks!

 

[Nessism]

Your bike is a 1982 MY, not 1983.

A rear diff from a 1983 MY bike will lower the revs some...

gear ratios by nessism, on Flickr

 

[wyly]

Hi guys,
I'm a recently new member to GSR, though I've been lurking around the forum for a while now. This is my first post so please forgive any early gaffes regarding forum etiquette.

Over the winter, I purchased a new-to-me 1982 GS1100G. With the help of the forum I was able to get the bike well-sorted, with new o-rings from cycleorings.com, new clutch springs, fibers, and lever from partsoutlaw.com, valve adjustment, fork rebuild, carb adj. & synch., etc. The bike runs great and starts instantly, hot or cold, and pulls hard throughout. There is a wealth of knowledge here, and it was instrumental to the resurrection of this bike. Thanks to all involved.

The question I have concerns gearing on this machine. At 70 mph (verified by GPS speedo), this particular bike is turning an indicated ~5100 rpm. The build date on the headstock is 2/82. The engine code on the case is U701-108xxx which, if I am correct, should mean this is an 1100. According to the gear chart I found here, my bike should be turning almost 1k rpm less at speed.

(I tried to place the chart here, but couldn't post the .jpeg. Sorry.)

There is NO clutch slippage. The bike will easily get air on a 1-2 shift, and all the secondary and final drive components are in great shape. I am running a Metzler Sportec in 130/90-17. According to everything I have read here, there is no combination that will allow this high cruise rpm on an 1100.

Concerning advertised top speed: Did Suzuki determine top speed as a calculation of engine rpm or by actual performance? If you do the math, my bike is running approx. 123 mph @ 9000 rpm. This bike will easily pull past this. With the lower listed cruise rpm, this works out to 147 mph. Quit a difference.

I have searched quite thoroughly and not been able to find this particular issue anywhere on the forum. As stated previously, the bike runs great and doesn't seem to mind the revs, but I do a fair amount of highway driving and think it may benefit from a lower cruise rpm. Did Suzuki ever throw together any oddballs out of leftover parts? I know it's not uncommon for auto manufacturers to do so during model year changes, but... ?

Can anyone help identify what I have? Thanks!

I'd say someone has swapped the oem sprockets out. I just changed my sprockets for better cruising range on the highway, as I have it now I should have a top end of 160MPH, rpm at cruising/highway speeds is in the 3 to 4K rpm range. I gave up some acceleration but I have enough added hp to make up for that.

Go here https://www.gearingcommander.com/index.htm feed in the relevant data for your bike. It'll give you the oem setup and input the gearing/chain setup as it now is and what it will be with any changes your thinking of.

 

[Rich82GS750TZ]

Wyly, it’s a G. No sprockets.

 

[wyly]

Wyly, it’s a G. No sprockets.

:highly_amused: oops I didn't notice that

 

[Guest]

Nessism, thanks for the chart. Same one I tried to upload and couldn't. Also fixed my signature. Although the bike is an 82, it's titled as an 83. Still mess that up now and then.

I understand I can install the later differential to lower cruise RPM, and may do so at a later date. My main concern right now is what do I have? I want to understand what I am riding.

Even if it had an 83 gkd engine or the trans gearset from one installed (possible, po had no info about the bike), it would still require the secondary set from an 850, which from everything I've read, will not fit. Any thoughts?

 

[Nessism]

The secondary gears from an 850 won't fit in the 1000/1100 engine case.

Most likely your tach is reading wrong.

 

[Guest]

Tach inaccuracy could certainly be possible, though I would think that it would err on the low side. Operation is smooth and steady, with a properly lubed cable. I guess it needs to be checked against another tach. I'll get back in a day or so after I check it out.

 

[Nessism]

Your bike should have a 17" rear wheel. If someone installed a 16" the rpm's will be higher.

 

[Guest]

It does. I am running a Metzler Sportec size 130/90-17.

 

[Nessism]

If you look at the chart you will see that the only variable in play is the 5th gear ratio and the final drive. And it seems extremely unlikely that someone changed the transmission.

 

[Rob S.]

For what it's worth, my 11E (stock gears) revs higher than the Cycle World review says.

 

[Guest]

Trust me, I understand. That's what has me baffled. Even with the gkd 5th gear and the low ratio differential, there is still a substantial difference in rpm with the secondary set these bikes came with. I know the 850 units won't fit, because the hive said so. At the same time, there is some explanation for the apparent discrepancy i am experiencing with this particular bike.

I'm gonna check the tach calibration tomorrow against an electric unit. If that's good, I'll start pulling gears and counting teeth.

 

[Nessism]

Did you look at the cylinder to make sure your bike doesn't have an 850 engine?

 

[Guest]

I was pretty sure, but i just looked again. No markings on the cylinder. Had a few kz's that had them, but none here. The only numbets are on the case by the oil fill plug. U701- designates a 1000-1100 cc engine. Mine is supposed to displace 1074 cc, correct?
.

 

[salty_monk]

Or a 1000 engine....

From memory the 5100 at 70 sounds somewhat close to what my 1100G used to run.

 

[Guest]

If it was a 1000, the first character in the engine code should be a T as they only displaced 997 CC's correct?

And it was mistaken as to the displacement range for the U engine code. The range is 1000-1099 cc.

Salty Monk, are you speaking of the 1100 G in your signature? If yours was turning as fast as mine is did you ever have to go into the secondary? I was just wondering if maybe you verified gearing if you were in there. There's definitely something up that's not allowing my bike to align with this gear chart.

 

[Rob S.]

From the July 1982 Cycle World test of the new, very different 11E:

"Engine speed at 60 mph: 3811."

I have the following in my (bought at least third hand in 2013) personal 11E notes:

4300 rpm at 60 mph

5000 rpm at 70 mph

Now here's what may be a factor from the mag article:

"Speedometer error:

30 mph indicated, 29 actual &

60 indicated, 58 actual."

We've all known that manufacturers speedos are optimistic, in fact I'm a little surprised that 60 on the dial is as fast as 58. That might account for some of your "high rpm." BTW, it says mine is, at stock, geared for 142 mph.

 

[bwringer]

Let me offer another viewpoint: this is a feature, not a bug.


Why are you worried about this? There's absolutely nothing to worry about here.

This "problem" is not a problem in any way, shape, or form whatsoever.

You have a GS that runs great. Go forth and ride, and be happy.

It is very possible, in fact it's certain, that the speedo and tach are not completely accurate. They were never precision instruments, and the passage of nearly four decades has not improved them. It doesn't make much difference, other than you should probably ride around with a GPS or a speedo app on your phone for a bit to learn the speedo discrepancy so you can mentally correct.

One of the most common questions new shaftie owners have is "How can I lower RPM on the highway?". The answer is "you don't". The engine is designed to spin, it loves to spin, and so the onus is on you to change your thinking and stop chugging and lugging around like a little old lady on a Harley.

In sum, grip it and rip it dude!

Yes, people change final drives around sometimes (not the secondary gears in the engine), but this makes a very very minor difference and is usually disappointing to those seeking a lower RPM experience for whatever unfathomable reason. That just isn't what the bike is.

 

[alke46]

What he said. I was thinking it but decided to stay out of it.

Bwringer is telling you how it needs to be done.