Low & Slow's Ninja 250 project

[low&slow]

After the recent Las Vegas to Barstow Vetter Challenge I have thought a lot about my future participation in these real-world fuel economy contests. While I'm pleased to have improved a 40mpg bike into a 60mpg+ machine I have to recognize the inherent disadvantages my Yamaha Vision ( 550cc shaft-drive bike) presents versus the 250cc gas bikes and the diesel bikes that have been the previous Challenge winners ( 134 mpg to ~ 157 mpg). I decided to start looking for a used 250cc bike to modify for future fuel economy runs.
After about 2 weeks of searching I found a 1999 Kawasaki Ninja 250 in good running condition for a good price and well under my project budget. It was a salvaged bike and so I had to have it inspected and the engine and frame #s verified to get it titled and registered for street usage.
I adjusted the valve clearances, sparkplug gap, cleaned and re-oiled the air filter and changed the oil and filter. I topped off the tank and rode it around running errands for a few days before doing my first official mpg calculation: 65 mpg.
Today I rode with Alan Smith( Ninja 250 streamliner ) and another stock 2008 Ninja 250 as well as a Triumph 1100 and a BMW 1200. We topped off our tanks at the start of ride and refueled at the end of the ride 126.7 miles later. The ride was at a spirited pace on twisty backroads on a cold day with with about 15 freeway miles on the way back. Alan got 89.47 mpg, the 2008 ninja got 62.1 mpg and I got 72.8 mpg. I was pleased with how the bike runs and how well it handles. It was interesting to compare the 2 stock ninjas with Alan's to see how effective his modifications are.
Now that I have my baseline I'm ready to start my modications. I'll start with a larger countershaft sprocket ( 15 tooth vs 14) and larger windscreen. I'm pleased to already have beaten my best tankfill on my Vision 550cc ( 66.8 mpg) . I'll try to keep posting on my progress.
Happy New Year , L&S

[redyaris]

Looking good L&S
What you mite also be able to experament with is shrouding and boat tailing behind the rear wheel attached to the swing arm. I suspect you will find some "very interesting results" at this stage of development...

[low&slow]

Thanks, a long tail is definitely in the near future as well front and rear wheel shrouding

[FXSTi]

I don't usually subscribe to threads, but I'm making an exception.

Are you planning a fuel injection set-up?

Kirk

[low&slow]

Hi Kirk, No current plans for fuel injection so far but I wouldn't rule it out. I haven't looked into it much yet and the only potential drawback would be the cost. The gearing and aero mods are cheap and very effective so I'll start there.
all the best , L&S

[redyaris]

I just looked up sprockets for the EX250 and PBI sprockets has the largest range; fronts are 13 - 18 teeth and the rears go from 33 - 60 teeth. what I am wondering is will the EX250 accept a bigger than 15 tooth front sprocket without having the chain/sprocket contact the case? for the rear going from 39 teeth to 33 teeth is a 15% reduction so 6500 rpm will be reduced to 5500rpm if you can add a 16 tooth to the front then an other 6.6% rpm reduction drops the rpm down to 5150rpm at 70 mph. at this point the full benifit of the aerodynamics will be achieved.

[low&slow]

Wow! fast research. From what I've read 16T on the countershaft sprocket needs grinding for clearance. I'll pass this on to Alan.
many thanks L&S

[redyaris]

I've "bin dare dun dat" more than once for mini road racing bikes and hare scrambls. PBI Sprockets will also make custom sprokets if a few of you EX250's can arange for a batch lot order. Maybe you's can get down to a 15/30 setup on the ninja 250's, which would drop the rpm down to 5000rpm at 70 mph.

The only problem that may present itself is starting in first gear, specialy on hills. My Suzuki GS 500 [Gray] required a little more careful/gradual clutch engagement when starting out.

[BHarvey]

It'll be interesting to see how it goes. Considering getting one myself.
I'd recommend some Avon Road Rider tires as they roll very well and have great wet and dry grip.

[low&slow]

Report #2 After getting the baseline for the Ninjette ( 72.8mpg ) I could hardly wait til I started doing some mods. I haven't bought sprockets yet so I decided to start modding the front end of the bike. I removed the windscreen and front fender . I made a longer, taller windscreen out of coroplast and mounted it on the stack faring. I made a fully faired front fender out of sheet metal, coroplast and some outdoor sign stock. Since I'm going with a Vetter tail, I just bungeed on a plastic trash receptacle behind me until I start building the tail. I need to do another run see how it works. more to follow.
all the best, L&S