KZ 400 Rpm question.

I just recently bought a 75 kz400 and in 5th gear at 45 mph I'm running 4500 rpm,at 65 mph it's 6500 and so on.is there a way to change my gear ratio to bring my rpm's down at high speeds

Installing a front sprocket with one more tooth makes a nice difference for freeway riding. You have to check if there is room on the engine first and also make sure the chain is long enough. Upping the gearing any more than this and the bike will feel like a dog at low rpm's. The 400's are designed to spin so let them.

So it won't hurt it to run at 6500 for periods of time

eulis wrote: So it won't hurt it to run at 6500 for periods of time

Every machine has a 'Cruising' speed where it and you, the rider, agree things are good. For some bikes 65 MPH is a stretch. I suspect that might be the case on a 400 at 65 MPH. Still if you can bear it:
As Nessism said "Let it spin."
Keep the oil clean and pay attention to the maintenance schedule.
Bill

Nessism wrote: Installing a front sprocket with one more tooth makes a nice difference for freeway riding. You have to check if there is room on the engine first and also make sure the chain is long enough. Upping the gearing any more than this and the bike will feel like a dog at low rpm's. The 400's are designed to spin so let them.

If there's no room for a larger front sprocket, dropping 2-3 teeth on the rear sprocket will give the same results.

Nerdy wrote:

Nessism wrote: Installing a front sprocket with one more tooth makes a nice difference for freeway riding. You have to check if there is room on the engine first and also make sure the chain is long enough. Upping the gearing any more than this and the bike will feel like a dog at low rpm's. The 400's are designed to spin so let them.

If there's no room for a larger front sprocket, dropping 2-3 teeth on the rear sprocket will give the same results.

Yes, this can be done also. One tooth in the front is equal to about 3 in the back since the stock ratio is pretty close to 3:1

Stock tooth count is 15 front and 45 rear.
Or 45/15 which equals 3.00/1.
You will have a hard time finding anything other than a 15 front.
I have a 33,38 and 41 rears. They are out there you just have to look.


.

Playing around with drive ratios can be informative and all the comments you've gotten here are golden. There is one thing I know about Ma Kaw, and that's that she generally knows best. My bet is that after you've lowered the final drive ratio, you'll get that easier cruising at 65 MPH but you'll loose driveability around town. At least that was my experience when I tried the same thing on my KZ900.
Just Saying.
Bill

Thank you guys for the advise,I may just leave it as is.bike runs and looks too good to be messing with it

eulis wrote: Thank you guys for the advise,I may just leave it as is.bike runs and looks too good to be messing with it

Good Decision!

Could be normal RPM range for a 400. Many years ago I let my buddy who had a 400 borrow my 74 900. He came back with a ticket because he said he watched the TAC more than the Speedo. At 60 MPH my 900 Tac shows 4K or there abouts.

Other KZ400 owners might weigh-in here but I recall the last time I was on the freeway with my '76 I was closer to 5K RPMs at 65. I need to get it out so maybe I'll wind it up at little and report back.