Engine rpm related to actual mph?

OK strange question of the night...

I have a 1977 KZ650B1 I've been rebuilding for the past year or so... it is mostly stock, mild cafe mods like low bars and bar-end mirrors but little messing with the mechanicals. I do have pod filters and I've got the jetting pretty dialed in. It has a new chain and sprockets (16T front, 42T rear) and new tires as well.

Now then... as I buzz down the road in town I hit 30mph or so at 4,000 rpm in second. I can puddle along at 30 - 35 mph in third at 3,000 rpm or so. On the highway in top gear (fifth) I'm doing 60 or 65 at 4,000 - 4,500 rpms. I have a 9,000 rpm redline. The sprocket sizes I listed are what was given in my Kawasaki manual.

There is a chart at the front of my manual that lists road speeds for each gear in kilometers, doing the conversion for top speed (.6214 miles per kilometer roughly) a listed speed of 220 kph is roughly 112- 115 mph. I'm halfway there at 4,500 rpms, am I on target or geared too tall?

I'm trying to set this bike up for putting into work and back.

Tall gearing means your gears are long. Sounds to me that your back sprocket was raised (teeth), or your front sprokect was lowered, or both; this would lead to lower gearing, which is accelaration.

you are on target with the chart
speedo may be reading a tad high which is common...

It sounds normal, similiar to mine. here is a link to a neat chart. Plug in your info into the pink area. Play around with sprocket sizes, tire sizes, and see what you get. With stock B1 info you will see a top speed of 115-117 mph.

www.wotid.com/tls/files/gearing_v12.xls

Post edited by: OKC_Kent, at: 2007/05/15 23:48

that sounds about right to me, havent rode the 650 in a while though. tire size will change the rpm some dont know about bikes, but on the race car 1 inch is equal to about 100 rpm change up or down

I've asked before, but never got an actual answer.. Is it possible to change the gearing on a shaftie, to lower it a little, so that my 60mph is below 5grand rpm? It sits around 5250 right now.

I don't think it is very easy to change the final drive ratio on a shaft-driven bike. You'd have to go in and figure out a way to modify or replace one of the gears in the shaft drive setup somehow I believe...