I wanted to throw this out there for anyone looking at either of these bikes for commuting, first bike, etc. I know they are completely different and usually aren't compared with each other given the ninja 250 is in a class all it's own when it comes to 250 street bikes. But in looking for a gas sipping commuter bike I was able to get both a 2001 Suzuki GZ250 and an 06 Kawasaki ninja 250 for under $1000 for both so I figured I would register and ride both and then sell the one that didn't suit my needs. I am keeping both bikes for the following reasons.

The GZ250 gets better gas mileage and with the single cylinder thumper engine has much better torque for stop light to stop light driving and speeds under 50 mph. This will be my main commuter bike to and from work never exceeding 50 mph and driving a combined 20 miles per day. I have shaved 30lbs or so from this bike as I am making a bobber out of it. Also it has been rejetted, pod filter added, and exhaust is cut. The first gear on this bike is almost useless because of how fast it needs to be shifted to second. Although the transmissions shifting is so smooth, just like every suzuki I have ridden, that it isn't too big of a deal. It will idle along in 5th gear and 25 mph and has enough torque that downshifting usually isn't necessary. The GZ is air cooled, single cylinder/single carb, extremely easy maintenance.

The Ninja 250 is so much better at speeds over 50mph. The braking and handling are not even in the same ball park so I will be keeping this one for my freeway rider/weekend canyon carver bike. This bike is no doubt faster than the GZ, even with the GZ being rejetted and 30 lbs lighter than stock, but the ninja definately requires more throttle for launching quickly from lights and requires downshifting to get into the power especially as slower speeds. The suspension, braking, and high rpm power make this bike shine when there is room to open it up alittle. The ninja really doesn't require much maintenance either but things like adjusting the valves and carb syncing are definately harder and more time consuming than on the GZ

I would be happy having either of these bikes as my only bike but if I had to do much freeway riding the ninja would be my pick. For a commuter only bike I would pick the GZ.

Neat comparison, thanks for sharing!

What mileage are you getting with the GZ?

I am getting 60-65 mpg on the GZ. This is commuting only stop and go with speeds no higher than 50-55 mph. The ninja 250 was getting 50-55 mpg on the same commute.
Once I get on the freeway cruising 65-70 mph they both get around 65-70 mpg though. And the ninja cruises those speed much better than the GZ.

I am getting 60-65 mpg on the GZ. This is commuting only stop and go with speeds no higher than 50-55 mph. The ninja 250 was getting 50-55 mpg on the same commute.
Once I get on the freeway cruising 65-70 mph they both get around 65-70 mpg though. And the ninja cruises those speed much better than the GZ.

With the torque you mentioned on the GZ, I would try to locate and install a 16 tooth front sprocket. I do not have experience with the GZ but I did this with the Ninja 250 and besides a little more clutch slip to launch, it made the shifting much more like a big bike. We were able to actually use 1st gear and 2nd would run up to 30mph instead of 21 with the stock 14 tooth unit. With my fat 200+lbs aboard the bike would still top 100 mph and it can easily be switched back if necessary

I have been looking into changing the gearing on both bikes actually. I will probably wait until they require new chains though as I hate wasting anything lol.