According to the chart in this thread, I should be turning 4186 rpms at 70 mph. At that rpm I am barely over 60mph. I have the standard 16" rear wheel. Any ideas what is out of whack? http://www.thegsresources.com/_forum/showthread.php?t=148442&highlight=final+drive+ratios
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rpms at 70mph
- Thread starter 1948man
- Start date
S
SqDancerLynn1
Guest
You could have the 3.09 rear gear
Thanks for the ideas. Steve, I have a little hand held GPS that I checked the speedo on my previous bike. Had to remain steady for 20-30 seconds for it to settle out but I will definitely try that. Lynn, according to the chart, a 3.09 final gear would produce the symptoms I am experiencing and I'm not sure if the history of the bike I got is correct so that could well be it. Jim M
You can only expect 25 to 30 year old analog instruments to offer vague approximations of actual RPM and speed.
Then again, when I mounted a GPS to my 850G with 110,000 miles, I was shocked to find that the speedo is dead on.
Then again, when I mounted a GPS to my 850G with 110,000 miles, I was shocked to find that the speedo is dead on.
Doh!! I looked in the owner's manual I downloaded from Cliff's site and it confirms Lynn's idea that maybe I have a 3.09 final ratio. I guess I should have looked there before going with what the chart said. This would suggest I should be about 4445 at 70 mph and 3810 at 60 mph.
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If it's an '83 it has the 2.9 gears in back. I put an '83 1100GL rear end in my 850 and can confirm those numbers. The rear end difference is not all that great by the way, only about 300 rpm or so at freeway speeds.
Yeah, I was looking at my cyber manual and it seems kind of generic, like maybe it was printed for the '82 model. Hmmm. The rpms seems to point towards the 3.09, maybe they used some 3.09's and some 2.91's in the '83's or maybe it's my speedo. Or maybe the PO replaced the original.
twr1776
Forum Mentor
When was yours manufactured? I just looked at my 83 and it was 9/82 and I have the 2.91 as near as I can tell. If yours was manufactured earlier it could be you got the 3.09 from the factory. Suzuki tended to use up all of last years parts before going to the next years production run.
The parts fishe only shows the 2.91 gears, no mention of 3.09's for '83. Also, 9/82 is September, so that's an early 1983 model.
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sscott
Guest
Just a guess here but could the tachometer be off?
Is there someone you can ride along with (safely of course) and compare speeds to? Might help
Is there someone you can ride along with (safely of course) and compare speeds to? Might help
I'll check with the GPS as close as I can. Just curious, how do you determine the specs of a part from the parts fiche? I looked under "propeller shaft" at Alpha sports and can see how everything goes together but can't figure out what the ratio of the final gear shown is.
Calculate the ratio: Driven gear # teeth / Drive gear # teeth
Why didn't I think of that. Checked speedo with gps and gps says 63 mph when speedo says 60mph. Actual speed is 5% higher than indicated speed. Guess that accounts for the bulk of the discrepancy. Seems most newer speedos read 7 to 10% error in the other direction.
iI would verify that at more speed vs indicated RPM points to determine that it is linear. Where I have checked this, the tach is linear, but the speedo gets farther and farther out, percentage wise.
I checked my GS1000 with a GPS and it read +5% up to 60 mph and then gradually changed to -4% at at 125 mph with 100 mph being bang on and according to specs and calculations the tach seemed pretty close at all GPS speeds. So until you figure out where your speedos at it will be hard figure out where your tachs at.
Mine was off 1.5 mph at 30 mph and 3mph at 60 mph. both times reading conservative. That's as near as I could tell with my handheld GPS, holding steady for 15-29 seconds. For my purposes, I'll just subtract roughly 5% from my indicated speed. I don't visit the over 85mph range often.
Steve
GS Whisperer
How close is the odometer?
What size front tire do you have on your bike?
If you go to the next larger size tire, you can slow down the speedo so it's accurate, but it will also slow down the odometer.
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the odometer is only reading a distance as calibrated to a constant.This constant being the turning of the speedometer. So if you put a larger tire on and the speed on the speedo is verified to be reading correctly by a radar gun or whatever the odometer will read correctly. Changing a tire to a larger or smaller size has nothing to do with the odometer..It all boils down to how fast the speedo cable is spinning.
I guess i should say it like this::
Smaller tire than what the speedo was ORIGANALLY calibrated to = faster rotation of the speedo cable..the speedo may say you went 1 mile when in fact you only went 8/10 because of the varience
Larger tire than what the speedo was ORIGANALLY calibrated to = slower turning of the speedo cable. The speedo may say you went 1 mile when in fact you went 1and 2/10 miles therefore in either case the SPEED will read incorrectly...either your going faster than it says or your going slower..
Smaller tire than what the speedo was ORIGANALLY calibrated to = faster rotation of the speedo cable..the speedo may say you went 1 mile when in fact you only went 8/10 because of the varience
Larger tire than what the speedo was ORIGANALLY calibrated to = slower turning of the speedo cable. The speedo may say you went 1 mile when in fact you went 1and 2/10 miles therefore in either case the SPEED will read incorrectly...either your going faster than it says or your going slower..
