Changing front sprocket

I have a 1980 KZ750G twin, 5 speed and I am looking to get more speed out of fewer RPM's. It has a stock 16 tooth front sprocket on it now and wasn't sure about going smaller or larger with it. Is there a better ratio to go with if I change both the front and rear sprocket or am I better off just changing the front? For me to do 60 mph on the highway it runs about 4,900 rpms.

I'm no pro, but typically I've seen guys change the rear sprocket before changing the front. A smaller rear will give you a "longer" gear ratio which means more speed with fewer rpms but slower acceleration. Opposite with a larger rear sprocket.

Here's a website you can use to figure ratio's with new sprockets, and tire size: www.gearingcommander.com

I chose the other route when replacing both sprokets and chain. 17T front (16T standard) and 38T standard rear fit with a standard 106 link chain. 17T fit without removing the sheet metal chain guard. This dropped about 500 RPM at 60 MPH.

While changing sprockets, I had a tough time getting the side cover off around the side stand spring stud. I fixed that with a file while I was at it.

Makes removal for changing oil easier also.

i've always thought changing one tooth on the counter sprocket {front} equates to about three on the rear..

brianrae33 wrote:

i've always thought changing one tooth on the counter sprocket {front} equates to about three on the rear..

That is accurate for a stock 750 twin which starts out geared 16/48. Going up to 17 on the front is the same as dropping to 45 on the back.

Techhead0_3 wrote:

I have a 1980 KZ750G twin, 5 speed and I am looking to get more speed out of fewer RPM's. It has a stock 16 tooth front sprocket on it now and wasn't sure about going smaller or larger with it. Is there a better ratio to go with if I change both the front and rear sprocket or am I better off just changing the front? For me to do 60 mph on the highway it runs about 4,900 rpms.

Wierd, my 750 twin with stock gears spins 5000 @ 70 mph (about 4300 @ 60 mph). Make sure you have the stock 38T on the rear, sounds like you don't.

You can put a 17T on the front and drop the RPMs about 6%.

You will need to buy a big socket to fit the front drive shaft nut. Keep the rear wheel on and hold the rear brake when you crank on that nut. It will also have some kind of locking washer on it you need to clear before the nut can turn.


FYI: I am running 17 / 38 on my 750 twin right now with a 110-90 rear tire, and I wish the gearing was higher. I think optimum for me would be about 17/36, or even 17/35 with that size tire FOR SMOOTH CRUISING ON THE EXPRESSWAY. Just my opinion. Of course, you do give up some acceleration for this.

However, if the rider is heavier than me by a lot (I weigh 170) the bike might lug too much geared 17/35.

YMMV

if your changing your gearing it is always easier and cheap to change the front sprockets and 1 tooth on the front is around the same as going down 3 teeth on the rear.