For 2017, Kawasaki went to work on its quarter-liter race bike changing up the frame, engine, intake, airbox, swingarm, radiators, seat, tank, linkage, shock spring, fork spring, and a number of smaller changes. Suffice it to say, there are very few interchangeable parts between the ’16 and ’17 bikes. All of these changes were aimed at making the bike lighter, a claimed 233.6 lb. curb weight which is a 3.75 lb. savings over last year’s bike.
There are quite a few engine changes to the motor and intake system that really did translate to a different feeling bike on the track. The cylinder has a new 7-degrees more forward offset that results in the downdraft intake having a more direct line to the the combustion chamber. Also the second of the dual fuel injectors is all new and has 8 spraying holes instead of four. The cylinder head has a new process of machining after it is cast, not unlike what race shops do. The piston is 6 grams lighter, has a bridge-box bottom design that is stronger, and has a Molybdenum coating to reduce mechanical loss and reduce wear. On top of the engine the valve train has been lightened by titanium valves, revised exhaust camshaft, revised camshaft sprocket, and a slimmer and lighter cam chain. The last of the engine changes is lighter flywheel aimed at creating a quicker reving motor.
Did we feel all of these changes on the track? Absolutely. While the 2016 KX250F had a punchy, thick feeling power, the lighter engine on the ’17 model definitely revs quicker and has more exciting power. Yet, we wonder if they made it too quick reving since we were grabbing gears sooner than we’d like. The motor reved out to the limiter before we thought it should, especially with the white (more aggressive) coupler. The stock green coupler had OK bottom, great mid and pretty good top end and over rev. So, to get the best of both worlds, Kawasaki made a map that is somewhere between the green and white couplers by just leaning out the fueling in the first 50 percent of the power. The result was a better, more exciting hit on bottom with no detriment to the top end power. This was both testers favorite setting for the day.
The front of the Kawi still has the Showa SFF Type 2 Fork with one side having a spring and the other side handling all of the damping, yet they revised the valve settings and put in a stiffer spring (9.8 N/mm from 9.6 N/mm). Also the inner fork tubes are thicker for more rigidity and a new coating on both the outside of the inner tube and the inside of the outer tube for less friction. The front of the bike also sees a more rigid bottom clamp for more precise turning.
Out back the spring is both physically lighter and has a lighter spring rate (52 N/mm from 53 N/mm) and shock has new settings to match all of the chassis changes. On the track, there wasn’t a massive difference between the ’16 and ’17 bikes as far as suspension goes, but we did notice how smooth the fork action was, which was more comfortable without giving up performance. Our faster ride went four clicks stiffer on the fork while our vet-speed rider preferred the stock setting.
The knuckle and tie-rod were revised and, perhaps because of this, changing the sag setting on the KX250F has a massive difference on handling and front-end feel. The suggested sag range is 100 to 110 mm with a sweet spot at 105 mm. One of our testers normally prefers a little less sag so he started at 100 mm which actually made the Kawi twitchy and put too much weight on the front wheel. Dropping it down to 106 made a huge difference and balanced the bike out.
Other than the engine changes this was probably the biggest area of change on the bike. The frame spars are closer together, the front downtube has a new design, and the radiators have been angled inward to make the shrouds 1.3 inches slimmer. The seat has a flatter profile and the seat base is reinforced with a new seat hook. The tank is a little bit larger (1.6 gal. to 1.7 gal) but sits lower in the frame increasing mass centralization. The swingarm is new with the changes aimed at reducing weight.
Now, Kawi’s have had a reputation of being rear-end steering bikes and while we won’t go as far to say as the KX250F is now a front-end steering bike, we would say that the bike is more of a neutral steering bike and with a few adjustments could be either a front or rear steering bike. Both of our testers consider themselves more front-steerers and had a very easy time getting the KX-F to corner. While the ’16 bike had a little bit of a lazy handling feel and was sluggish to change directions, the ’17 machine is much quicker and more willing to respond to rider input. The lighter weight and new seat orientation combined to make the Kawi easier to lean into a turn and keep it tucked into a rut.
If there are any downsides to the new chassis and lighter weight of the bike is that, after riding the ’16 and ’17 bikes back-to-back, the newer model loses just a tiny bit of Kawasaki’s trademark stability. But both testers would happily make the trade of a little less stability to get the quick handling and easy turning of the new bike.
After a day of riding at Zaca Station it is safe to say that the changes to the 2017 Kawasaki KX250F were a move in the right direction. The motor changes make the power quick reving and exciting and with a few adjustments can be really fun and fast powerplant, while the chassis changes and lighter weight make the KX-F more responsive and easier to ride. We’ll have to wait for the 250F MX Shootout to see how the green racer stacks up against its cohorts but we have a feeling, a very strong feeling, that it will do quite well.