Sprocket selection for KZ/GSXR swingarm

'82 KZ750 with an '04 GSX-R rear swingarm

So after enough reading and researching I have a firm grasp on what I need to do to get this completed.......except when it comes to the front sprocket and chain.

Three issues I am running into:
-With the swing arm being wider, how do I align the chain with the front sprocket?
-How do I select the number of teeth for the front sprocket to get it as close to the gear ratio as possible?
-How should I calculate chain length?

KZ750 sprockets are 13/32 and uses a 630-84 length chain.
GSX-R sprockets are 16/45 and uses a 525-108 length chain

could use stringline off rear sprocket after tire is perfectly centered.are you using gsxr tire as well?as far as chain length goes I would probably buy the chain with extra links plus the master.

Yeah ill be using the rear GSX-R everything. I was lucky and was able to get everything from the swingarm bolt back as one assembly.......and for $100

maybe this will help you.

www.gearingcommander.com/

leon

Awesome thanks Leon. That definitely does help.

As far as gearing, if the stock gearing is 13/32 = 2.46 final ratio... You want to match your gearing to your motor and consider the difference in rear tire circumference... You can do this mathematically!

I do not think you will find a 32 tooth GSXR rear sprocket... But you can run a 17/42 for a 2.47 final Ratio... As a base line!!! A 17 tooth front sprocket is 100 times better than a 13 tooth front sprocket....

Now, if the rear tire is 10% smaller then subtract 10% to the final ratio...

Finally consider if you want acceleration or lower cruising RPMS... Personally, I prefer decent acceleration... I would use a 17/43 for a 2.52 final ratio, (Taking into account the smaller rear tire and all).

For the chain, I would buy a 120 link chain, and use what you need...

Luis

Here's a simple method to closely match your current final drive ratio while using the smaller rear wheel.

Measure the circumference of you original wheel/tyre (fully inflated) and divide that figure by the number of teeth on your original rear sprocket.

This will give you a distance travelled per tooth ( i.e 1/2 inch etc )

Now measure the new smaller wheel/tyre circumference and divide that figure by the (1/2" etc) distance travelled figure and that will give you the number of sprocket teeth you need to match your original engine revs to road speed.

You will end up with a smaller amount of teeth on the rear and maybe not exactly by a full tooth but use that odd fraction for the next step.

You now need to divide your new rear tooth count by your front tooth count to calculate the new ratio.

Use that ratio figure to work out the tooth counts for your new sprockets.

The 525 pitch will require more teeth for a given circumference compared to the 630 pitch, so to give adequate clearance for the swingarm pivot etc you may need 16 teeth on the front to equal the diameter of the 630's 13 tooth.


A point to note is that a tooth count of less than 14 teeth will produce a notchy drive and quickly wreck your drive chain due to the angles involved and 15 teeth is generally considered the lowest to use.

SBK Racer & zed1015

Thank you for the very informative posts. I learned more in 2 minutes of reading than an entire evening yesterday!

I run an 18 front 41 rear in a 520 pitch DID er3 chain around 60mph 5500rpm

Maybe this will help....

Sprocket Determination Guide

As in my case ZX6 rear end... Pretty much same gearing.
* Wanted to stay with the 630 chain.
* With that in mind, had to find a rear sprocket to match the ZX6 rim/hub....
Using several sources mentioned (JT Sprockets for example) found the correct bolt patterns,
spline info etc....
* KZ750 sprocket same pattern.
* Used a 1/2" Offset counter, based on sprocket tooth counts for desired gearing, all good.