When word first leaked about a new Kawasaki Ninja 250, pictures started popping up from Japan of a local tuner's take on the venerable beginner bike. Beet Racing had swapped the standard fairings for race plastics painted in similar fashion to that of John Hopkins ZX-RR MotoGP machine, complete with Hopkins' number 21. It also went on to swap a Brembo 4-piston caliper in place of the stock unit, a titanium exhaust system and a trick-looking prototype reinforced swingarm. Seeing this bike got the wheels in our head turning; what would a Ninja 250 really be like on the track?
Never one to let a good idea go to waste, SR approached Jeff Herzog, Kawasaki's Media Relations Manager, about the Beet bike and if there was any intention of taking these little buzzers to the track. The more we talked it became clear that we wouldn't just be taking a bike to a local trackday. Oh no, we were actually going to enter it in a competition. Herzog, himself a former Ninja 250 racer, liked the idea but didn't know where it would stand a chance in the local club racing scene. It was about this time that the Willow Springs Motorcycle Club announced that it had developed a new class, the Ninja 250 Cup. The premise around the series was to promote racing in the club for as little as possible through extremely limited modifications. And there was the answer we were looking for.
We sent the bike off to Carry Andrew and his Hypercycle shop to get it prepped for its racing debut. Our goal for the project was to build a proper, raceworthy Ninja 250 for $6000, including the cost of the bike. Why $6000? Because that's about the going rate for a decent used 600cc racebike. With the Ninja, one could have a new racebike that could teach the racing craft without the excess speed of a 600 or a 1000.
This aftermarket exhaust,...
This aftermarket exhaust, provided by Area P, was one of the first modifications we did to the bike. It just so happens you'll find it on every bike in the class. Our bike hovered around 30 horsepower just with this pipe and the appropriate jetting changes.
The Nuts And Bolts
Starting with a standard Ninja 250 ($3999), the stock exhaust was the first thing to go, replaced with an aftermarket carbon fiber unit from Area P ($495). To let the bike breathe properly, the ancient art of jetting the carburetors for that perfect air/fuel ratio was in order. Because the little 250 would be screaming at the top of its lungs most of the lap around Willow Spring's 2.5 mile course, proper main jets were the most important piece of the power puzzle. Surprisingly, the jetting is close to perfect straight from the factory, but after numerous dyno runs factoring in Willow's elevation, Andrews decreased the main jets from 98 to 95 with a Factory Pro jet kit ($89.95). The engine now produces approximately 30 horsepower, but more importantly the power curve is much more linear compared to the factory settings. While it may not seem like much, compared to the stock 250 there's a marked difference in mid-range punch as well as top-end power.
Jim Lindemann worked his magic...
Jim Lindemann worked his magic on the stock rear shock and simply added a piggyback reservoir, giving us the ability to adjust rebound and compression damping. This cost-effective solution only cost a couple hundred bucks and kept the rear end nice and planted.
Next, Jim Lindemann of Lindemann Engineering tackled the suspension work. Under the rules the rear shock is allowed to be replaced with an aftermarket unit, while the front fork tubes must stay in place (though internals may be modified). Stock, the Ninjette rear shock is only adjustable for preload, but instead of replacing it for a much more costly aftermarket unit, Lindemann simply installed a piggyback reservoir onto the stock unit for compression and rebound adjustability. This cheap solution proved more than adequate for a simple bike like this. Other aftermarket options available can cost upwards of $1000, but for just a tick over two C-notes the Lindemann route is hard to beat. The simple modification makes a drastic improvement to the rear of the motorcycle; whereas the stock shock is extremely soft, being able to add rebound and compression settled the back end nicely. After some experimentation with a prototype cartridge-style front fork system for the 250 that proved to be entirely too firm, we eventually reverted back to the standard front fork and left good enough alone.
That's it for the go-fast goodies. The next obstacle was making the green bomber look like a proper racebike. To do that, we removed the standard bodywork and replaced it with a set from Catalyst Racing Composites. The kit includes an upper ($289), lower ($226), tail ($189) and front fender ($93). For those really looking to save a few pennies, a catch pan underneath the engine capable of containing all of the engine oil is all that's really needed per the rules. Otherwise, simple number plates can be creatively attached to the front and sides of the bike to please the folks in timing and scoring. After that, little accents were all that remained. Steel-braided brake lines were added front and rear ($70) and Andrews accented the bike with a spare set of Sato rearsets he had lying around. While originally for a '05 Suzuki GSX-R1000, with some slight modifications he was able to bolt them up. Necessary? No. Trick? Absolutely.
The last piece of the puzzle was replacing the stock tires. Thankfully Kawasaki fitted 17-inch wheels to the bike, allowing the use of modern rubber. We chose to go with the Bridgestone BT-090 in a standard 110/70 front and a slightly oversized 140/70 rear. Look hard enough and you should be able to find a set for around $260--money well spent as the tires will last at least three--yes three--race weekends.