5200rpms at 70mph, too high!! kz1000m2

Hello everyone,
I've been really struggling to figure out why my rpms are so high from 5200rpm at 70mph on my fix-it-up kz1000 that I stole for $300. I should be getting closer to 4300rpm.

First thing to check was sprockets to make sure someone didn't change them; nope they're stock (15f/39r). Went to check them and the rear sprocket has 39 stamped on iy and I had to count the front but it has 15 teeth. I got really confused but then decided to check the wheels and tires; they're also stock. They are pretty worn but i dont think it would add a 1000rpm to my speed. I found this problem in looking to convert to a 530 chain and measuring rpm differences in different sprockets. I've put a couple hundred bucks into the bike to get it to run good by doing valve clearances, rebuilding carbs, and making sure everything works right. Another thing to note is that I AM getting into 5th gear.

Long winded but thanks!

Should be about 4550 rpm.  Did someone install a 16" rear wheel, by chance?

Edit: sorry, I saw the title and thought we were talking about a KZ1000 MK II.  My bad.  

You indicate you are getting into 5th gear when this happens, so what happens when you are in 5th and keeping it at 70 do the rpms drop or stay the same. 

It rpm doesn't change when I cruise. I figured out the tachometer was the problem by using my tach from my 440. Showed a solid 4300-4400rpm. Gonna tear at it in a couple days. 

The rear wheel is spokes and the csr has spokes wheels so I'd assume they're stock. aren't stock wheels 16 inch so it wouldn't matter? Anyways I swapped my 440 tachometer and it showed around the rpm you indicated so I'm to believe that the tachometer is the culprit. Is this the right line of thinking? If it is then I might disassemble it. I've had problems with this tachometer returning slowly so I wouldn't be surprised if there's more wrong with it. 

The M has a 16 inch rear same as the “K” sounds like the tachometer. If the sprockets are correct the only way the revs could be high is if the clutch was slipping 

If the tach doesn't solve your problem I would guess transmission as the next point to investigate.  KHI made a close ratio tranny that was long in first but short in the higher gears.  One way to check is if the bike is 1980 or older and has a plate over the kick start hole...it's probably a close ratio tranny.

hardrockminer wrote:

If the tach doesn't solve your problem I would guess transmission as the next point to investigate.  KHI made a close ratio tranny that was long in first but short in the higher gears.  One way to check is if the bike is 1980 or older and has a plate over the kick start hole...it's probably a close ratio tranny.

HRM, the bike is an "M2" which makes it a "J" motored 82 CSR

Is the Tachometer Cable or electric driven? You stated using a 440 tach so believe that would be cable. Has nothing to do with any trans configuration HRM. Haven't seen a CSR or 440 in quite a while, ha. 

bound wrote:

Hello everyone,
I've been really struggling to figure out why my rpms are so high from 5200rpm at 70mph on my fix-it-up kz1000 that I stole for $300. I should be getting closer to 4300rpm.

First thing to check was sprockets to make sure someone didn't change them; nope they're stock (15f/39r). Went to check them and the rear sprocket has 39 stamped on iy and I had to count the front but it has 15 teeth. I got really confused but then decided to check the wheels and tires; they're also stock. They are pretty worn but i dont think it would add a 1000rpm to my speed. I found this problem in looking to convert to a 530 chain and measuring rpm differences in different sprockets. I've put a couple hundred bucks into the bike to get it to run good by doing valve clearances, rebuilding carbs, and making sure everything works right. Another thing to note is that I AM getting into 5th gear.

Long winded but thanks!

The below calculator will give you speed in each gear and also help you choose the right sprockets for your personal requirements (highway cruising or stop light launches) when converting to 530

Gearing Commander - Motorcycle Speed and Drive Train Calculator v7

Thanks! I was thinking of going 18 in front and 44 in rear which would drop my rpm by 200 at 70mph. I don't want anything to crazy so I'm keeping the front sprocket the same diameter. Please let me know if there is anything to be wary of concerning the sprockets. 

Yeah the CSR was the only one that was cable driven that year... which works out well for me. I was thinking I would be able to swap the speedometer from a late kz1000p since they are also cable driven and those speedometer show up to 120mph while still looking stock. The only thing of concern is that the police bikes had a 18 inch front wheel compared to my 19 inch. I did a little research and the difference in speed reading was only like 3% or 2% which is pretty negligible.  Is the CSR uncommon or something?