TOPIC:

I am interested in changing my stock setup on my 750 to bring the RPM's down lower on highway travel, but am uncertain on what sprocket selection is good. Can I get away with changing the rear only? or do I need to do front and rear? or am I seeking something that won't really make that much of a difference? Any help would be great!

peachc wrote:

I am interested in changing my stock setup on my 750 to bring the RPM's down lower on highway travel, but am uncertain on what sprocket selection is good. Can I get away with changing the rear only? or do I need to do front and rear? or am I seeking something that won't really make that much of a difference? Any help would be great!

That's a twin, right?
Do you have the 16 front, 106 link sprocket, and 38 rear?
Get a 17 front if you don't have it. Mandatory.

Biquetoast wrote:

peachc wrote:

I am interested in changing my stock setup on my 750 to bring the RPM's down lower on highway travel, but am uncertain on what sprocket selection is good. Can I get away with changing the rear only? or do I need to do front and rear? or am I seeking something that won't really make that much of a difference? Any help would be great!

That's a twin, right?
Do you have the 16 front, 106 link sprocket, and 38 rear?
Get a 17 front if you don't have it. Mandatory.

Its the 4, I would have to look up the stock setup, the 17 front would make a big difference?

peachc wrote:

Its the 4, I would have to look up the stock setup, the 17 front would make a big difference?

Ah! Ignore everthing I said! I have no idea about the 4!!! Ah!!

My 550 had a 15 tooth front and a 38 tooth rear. Both were in real good shape with only about 1500 miles on them. Stock gearing on the 550 is 16/38. I replaced the 15 tooth with a 16 and at 55 mph it cut RPM's by about 400 - 500. The trade off is that the bike does not accelerate as fast but that's hardly noticable to me. Top end speed seems a little better but I find the lower RPM's at cruising speed a great improvement. Enough of an improvement to make me think seriously about trying a 17 tooth front sprocket. It shouldn't be any problem to change just one sprocket as long as your chain and the sprocket you are NOT changing are in very good shape.

You probably have a 13 front and a 32 rear, (that's what buykawasaki.com says) and it's 630 chain, you might be able to put a 14 tooth front sprocket on it, but I have ny doubts. Z1 Enterprises lists 13, 14, 15, and 16 tooth sprockets that are claimed to fit your bike, but I'd have to see one mounted on a KZ750H to believe anything larger than a 13 will fit, I tried a 15 tooth 530 sprocket on a 80 KZ750 motor, and it would have taken major modifications to make it fit. As in cut off the shifter shaft.

And Z1 does not list anything smaller than a 32 rear, so I think your best (and maybe only reasonable) option is to convert to 530 chain and sprockets, lot's more gearing options that way, and it bolts on.

For those of you who want to calculate what sprocket combinations will give you in terms of speeds and rpms then throw the following formula into excel. Keep in mind no driveline energy loss is taken into account.

Rear wheel radius (inches)= R
Wheel speed (rpm) = Ws = Es/Pr/Fr/Gr
Engine speed (rpm) = Es
Primary drive ratio = Pr
Final ratio = Fr = Wheel sprocket / Engine sprocket
Gear ratio = Gr

Vehicle speed (mph)= Vs = R*Ws*pi*2*60/12/5280


An example with the numbers off of my bike, 82 kz 750 twin. 16 front, 38 rear are as follows

Rear wheel radius (inches)= R=13
Wheel speed (rpm) = Ws = Es/Pr/Fr/Gr
Engine speed (rpm) = Es = 5000
Primary drive ratio = Pr = 57/23=2.47
Final ratio = Fr = Wheel sprocket / Engine sprocket = 16/38 = 2.375
Gear ratio = Gr = 5th gear = 21/24 = .875

Vehicle speed (mph)= Vs = R*Ws*pi*2*60/12/5280 = 69 mph

correction

vehicle speed = 75 mph

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