Kawasaki ZZR 250
 

I just bought a 1992 Kawasaki zzr 250.
i already changed gears for several motorcycles (here some models i already change).
-Yamaha 750 Super Teneré
-Yamaha XJ600 Diversion
-Yamaha YZF1000 Thunderace
-Kawasaki ZZR600
-Suzuki GSXF600
-Suzuki GN250
-Suzuki 650 V-Storm
-Honda NX250 Dominator
-Honda Africa twin 750
-Honda NX125
-Regal Raptor NAC125
-EUR R40
-EUR R25
-Keeway 110cc
...

I will fit to my kawa with a 15/33 gear (as i canot easely make it longer the 16 does not fit and 32 is too small for the holes). The 33 sprocket must be produced to fit . I dont plan to make any more changes for know and my goal will be to beat 2,7l/100 or 105mpg

good luck with it. keep us informed about MPG numbers. i was thinking about trying a 15/39 on my ninja 250 to see how much mine improved.

Prety soon i will have results on the 15/33 and will let you know. I am just waiting for the rear sprocket to be ready. I like cars and motorcycles with very very long gearbox so riding them is full of decision making. This way i dont get bored of driving. If i could design my own veicule i would probably have 8 gears to choose from. For me a gearbox is not ok when you can mantain cruising speed when uphilling 5% with last gear.

While the ZZR250 has different gear ratios than the Ninja 250, i still think 15/33 (2.20 final drive) will be too low and may actually be detrimental to your fuel economy.

I've crunched some numbers in gearcommander. If you have a stock rear tire (140/70-17), with a 15/33 you'll be doing 50mph at 4123rpms.

I've got a 15/39 (2.60 final drive) setup on my Ninja 250, and in 6th gear its a 1mph per 100rpm ratio, and seems perfect.... lugging the motor a little bit, bit not that much. Leaving from a stop i have to use a bit more clutch to prevent it from bogging.

I've found that cruising 55mph at 5500rpm is perfect on flat ground with this engine. If there is any sort of upgrade in the road, with a steady throttle position I'll lose a good 5mph or so, maybe 10 if its steep enough.

Thus, i'd advise you to shoot for a 1:100 ratio as well. For your bike, that would be a 15/40 setup, if you are using stock tires.

for 50mph i expect to be doing around 3900rpm. On stock geardrive i would be doing around 5800rpm.
These means 20,8Km/h - 1000rpm.

I have good experiences with Honda NX250 Dominator (i put 21Km/h-1000rpm) and Suzuki GN250 (i put 18,8Km/h-1000rpm) so i am pretty confident that zzr 250, than have more torque and hp, will be OK. Pretty soon we will know about it... I even made one YAMAHA XJ600Diversion 34,8Km/h-1000rpm with good results.

I will have the 55mph at 5500rpm on my 4th gear so i will be able to try your suggestion and evaluate differences, but why do you say its the best combination? based on intuition or is a math fact? I think and hope that going uphill may mean that i have to change gear, not only that will make my trips funniers (i like to make this kind of decisions while driving) but also it will mean that when i will be riding on straight or dowhill i can change gear again and low rev the engine.
For cruising on straight at 55mph i figure i will need abaut 8hp on wheel and i expect KAWA to have that power on 20%accelerator at 3800.

I have a back up plans as i will keep the 14 to front and i have a 38 to back so i can manage more combinations (14-33, 14-38, 15-38) also I will keep standard gear drive kit.

thanks for the info. i am now thinking about trying the 15/42 gearing, with a 140/70-17 rear tire next time i need a chain. maybe this will be a good compromise for me. i do like the sound of 5500rpm at 55mph though, but i do see the point about the bogging and lugging.

I just have my zzr 250 ready to go.
I didnt have much time and I had to adjust some parts (Valves painting change oil brakes....)
The final gearbox turned out to be 5000rpm-98Km/h(spedometer) and for me its perfect!
I was suposed to try to ride it slowly to see the mpg but didnt.... the engine is so fun to rev that i cant resist myself.(14.000rpm in a 250?!)

I already road it to 170Km/h in my forth gear.

Next days i will try to see how much it spends on fuel.