Normally when you think of motorcycle land speed racing you think about turbocharged, nitrous-injected, or big-bore engines. But since that's been done to death, it was decided that a risky new angle was in order: Build an `08 Ninja 250R. The stock mini-Ninja makes a monstrous 25.6 horsepower and pumps out a stump-pulling 13 ft-lbs of torque on the dyno in stock form, and can do about 98 mph flat-out with a tailwind. Getting one into the record books was going to take a lot more power and some changes to the chassis to get it over the 108 mph land speed record that we had as our goal.
A custom-fabricated set of...
A custom-fabricated set of JE pistons pushing a compression ration of 13.5:1 helped the little Ninja pump out 10.31 more horsepower than stock (35.92 horsepower at 12,200 rpm), an astounding 40 percent increase over stock.
Since comparatively few people race the Ninja 250, there wasn't a catalog full of go-fast parts for us to choose from; thus, we were forced to have virtually everything custom-made. First on the list was to consult Brian Weaver at JE Pistons, who worked with us to produce a custom set of forged stock-bore pistons that bumped compression to 13.5:1 (stock is 11.6:1). Next, we sent the cylinder head to APE where they focused on getting it to breathe better. Oversize (1.5mm larger) custom-machined titanium intake valves were installed, along with a full-radius Serdi valve job as well. APE also fabricated a set of adjustable cam sprockets and a billet cam chain tensioner.
Chris Hill at Performance Psycle in Knoxville, Tennessee was picked for the engine building and general bike prep. Hill has built many bikes for the AMA Dragbike series, including the 2007 National Champion in the ultra-competitive 1000cc SuperSport class, so we were confident that he would get the job done.
The first thing Chris did was to pull the stock airbox and replace it with: nothing. No pods, no screens--nothing but the Dynojet re-jetted carbs sucking as much air as possible (don't try this on your streetbike, though). Then an AREA-P/No Limits exhaust was installed that not only help produce more power but saved some weight, too. Part of going fast means reducing friction wherever possible, so Hill fitted the Ninjette's wheels with ceramic wheel bearings from WorldWide Bearings and slipped on a non-o-ring chain. With those two mods in place, pushing the bike around in the pits felt akin to pushing a 20-pound bicycle due to the low rolling resistance. Substantial gearing changes were obviously necessary, with a one-tooth larger countershaft sprocket up in the front and three-tooth smaller rear sprocket. Hill also removed everything on the bike that wasn't directly involved in making it go fast or stopping such as the mud flap, reflectors, mirrors, etc.
To help with rider aerodynamics, a custom "cut-down" tank was made by Liquid Visions. By lowering the top half of the fuel tank, the low profile design allows the rider to tuck completely below the windscreen and reduce aerodynamic drag. The chassis was also lowered front and rear to reduce the bike's aerodynamic frontal area as much as possible.
After final assembly, the Ninja 250R was filled up with Motul 300V synthetic engine oil and broke in on the dyno. After trying numerous cam timing combinations, the bike ended up cranking out 35.92 horsepower at 12,200 rpm and 16.79 ft-lbs of torque. The 10.31-horsepower gain amounts to a 40 percent increase over the stock powerplant.
In order to help tune the bike on the track, an Innovate DL-32 datalogger was also installed. As it turned out, however, data-logging was not even needed, with the bike set up so well straight off the trailer that it set a new class record of 111.30 mph on its first pass, with ECTA 200MPH club member Zack Millholland aboard at Maxton's Monster Mile course. Later in the weekend we moved the bike to another class and captured another record, but the strong headwinds ended up slowing Milholland down to 107.44 mph.
No, the little Ninja 250R will never be as fast as its bigger brothers. But this little Ninja is (currently) the fastest 4-stroke, naturally-aspirated, open-wheel bike in the 250cc class.