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RPM's at speed

  • Thread starter Thread starter waldo877
  • Start date Start date
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waldo877

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I have an '81 GS850GL, and at around 50-55mph, the RPM's sit at about 4,250 in 5th gear. Does this sound about right?
 
ShaftDriveGSgearratios-.jpg
 
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Seems like if the ratio stays the same throughout 5th gear you would expect about 3940 rpms at 55mph.
 
Nessism said:
ShaftDriveGSgearratios.jpg
Click to expand...
Hey Ed, you have one of these for the chain drive bikes? I know it would obviously change if you've changed the sprockets, or a 530 set up (tho you can get REALLY close to stock with a 530 set up as well) Id be curious to see exactly how far off my electronic tach on my 1100ES really is...
 
On my wife's 82 850L, I have checked the speed with a GPS and found the speedo surprisingly accurate. 55 indicated is actually about 54.2 on the GPS, and it's just under 4,000 rpm. I figured out that it's real close to 14 miles per 1000 rpm, so 4,000 should be 56 mph, 5,000 rpm should be 70 mph.

.
 
TheCafeKid said:
Hey Ed, you have one of these for the chain drive bikes? I know it would obviously change if you've changed the sprockets, or a 530 set up (tho you can get REALLY close to stock with a 530 set up as well) Id be curious to see exactly how far off my electronic tach on my 1100ES really is...
Click to expand...

Hey Josh,

To perform the calculation we need...

- primary reduction ratio though the clutch hub gear
- reduction though the transmission gears
- final reduction through sprockets
- total wheel + tire height = radius

Gather this info and I can make some calculations.
 
On my '80 850L, I have a 17" rear, always have had, the specs on the fender and the sticker on the head tube show the same size. My rpm at 55 (on GPS, speedo reads 59) is 44k-45k it's the first time I've seen the chart, the '80 850 GLT w/a 16" rear tire. I'm running a 130, but my new tire is a 120, I couldn't find anyone with a Perelli Scorpion M/T in the 130 size for some reason.
 
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Just to get ahead of your next question... these engines are incredibly durable and designed to SPIN. So grab that funny handle on the right and twist it hard and often. :twistedevil:

6,000 RPM and 80mph all day are no problem. In fact, the fun on a GS850 doesn't really begin until 6,000 rpm. Run it up to redline regularly -- it won't hurt a thing and you'll have more fun. :D
 
I guess you cleared up my concern Bwringer. Since I have a loud 4-1 setup, I got concerned that it was being wrung out too much for too long. I haven't even HIT 80 on it yet, but I guess I shouldn't worry about it now.
 
The top speed of an unfaired GS850 is about 115-120. In case you were wondering...

They will happily drone along the interstate at 85mph for several hundred miles, too.

Twist it up!
 
bwringer said:
Just to get ahead of your next question... these engines are incredibly durable and designed to SPIN. So grab that funny handle on the right and twist it hard and often. :twistedevil:

6,000 RPM and 80mph all day are no problem. In fact, the fun on a GS850 doesn't really begin until 6,000 rpm. Run it up to redline regularly -- it won't hurt a thing and you'll have more fun. :D
Click to expand...
True. I redline mine in 1st and 2nd, sometimes 3rd, but then I'm exceeding the speed limit by quite a bit so I have to shift up and back off.......:D
 
Dogma said:
Same on mine. Faulty chart?
Click to expand...

Sounds like a faulty chart. I know the guy who made it and it's not the first mistake he's made around here...:eek:

EDIT: Should be fixed now.:)
 
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Nessism said:
Sounds like a faulty chart. I know the guy who made it and it's not the first mistake he's made around here...:eek:
Click to expand...
Or Faulty tach readings...Ive found that these tach gauges, electronic or not, are not the most accurate from bike to bike...
 
I was just out on my bike and realized what I posted earlier was wrong. I have edited it, but my bike runs 44-4500 RPM at 60 on the speedometer (55 on the GPS).:)
 
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