RPM vs. Speed. What do you get.

I just went on a cruise and decided to pay a bit closer attention to the revs at speed. this is what my GPz1150 is getting. Mind you the gearing is not stock and will change again in the spring for a higher top end.

3K = 49Mph
4K = 65Mph
5K = 81Mph

This equals 16Mph per 1K in RPM. this test was done with a GPS along with the spedo. The spedo turns out to be quite accurate.

i have aa 80 kz750 ltd mine is:

3k = 40mph
4k = 50 mph
5k = 61mph
6k = 72mph

my stock gearing is 13/32

but according to www.gearingcommander.com/

website it should be different, so ,i think i may have a 12 tooth in front.

My final gear ratio at the moment is 38/15 (1:2.53) and stock was 41/15 (1:2.73) I will be converting to a 530 from the original 630 chain and going with a ratio of 17/40 (1:2.35)

With stock sprockets ( 35/15 ) I see 80 MPH indicated at 5K RPM. This on my KZ900.
Bill

I thought my KZ1100 shaft was turning over too fast on the highway but now I don't feel so bad. Using the GPS it goes:
3k = 45 mph
4k = 60 mph
5k = 75 mph

The Cycle World road test in 1981 showed 3640 rpm at 60 mph and the Motorcyclist test showed 3569 at 60. I don't know why mine is turning faster unless it's the tires (Kenda Challengers) on mine. Is there anything else that could affect it?

Only the front tire can affect it. I would check the variation difference between the GPS and your speedometer. I fiddled with mine until I got it with in 2% on the Odometer and right on the money on the Speedometer. This is all, using the GPS for calibration.

otakar wrote:

Only the front tire can affect it. I would check the variation difference between the GPS and your speedometer. I fiddled with mine until I got it with in 2% on the Odometer and right on the money on the Speedometer. This is all, using the GPS for calibration.

My spedo is off (found out with my GPS). How did you "fiddle" with it? What adjustments are you talking about? :blink:

Bluemeanie wrote:

otakar wrote:

Only the front tire can affect it. I would check the variation difference between the GPS and your speedometer. I fiddled with mine until I got it with in 2% on the Odometer and right on the money on the Speedometer. This is all, using the GPS for calibration.

My spedo is off (found out with my GPS). How did you "fiddle" with it? What adjustments are you talking about? :blink:

The simplest way is by picking the correct size front tire. Otherwise Kawasaki makes different size/pitch gears for the spedo drive unit. I am not sure how custom your bike is, and if you have a stock size front wheel or tire. I did it by disassembling the spedo and changing some gears and the return spring tension, but that is a He** of a lot of work. Still the best way is to put a larger os smaller front tire on the bike dependent on which way you have to go.

i would like to add that the rolling diameter of the rear tire does affect top speed. a larger rolling diameter tire will travel a greater distance than a smaller rolling diameter tire at the same RPM. so the larger rear tire will give a higher MPH.

Yes rear wheel size and sprocket size will affect top speed, provided that you have the torque to turn it. It however will not affect the indicated speedometer speed.

My build... Modified KZ900 15/37 sprockets... 17" tires.

65mph @ 4500rpms...

My '82 KZ650 CSR had stock gearing of (33/13)= 2.54, with 630 chain.

Using a GPS for indicated speed:

60 MPH - 4,950 RPM

I changed the front sprocket to a 14 tooth. (33/14) = 2.36 This yielded:

60 MPH - 4,600.

Even with the 650, it has plenty of torque to run at most any speed. A larger engine, such as a 1000 could probably handle a 2.2 ratio if highway cruising is the goal.