Quacking Quartet
By TMX Archives on 20th Nov 06
THE four-stroke revolution continues with the thumping, lean, mean and very lime green, Kawasaki KX250F and 450 models having massive changes to their internals and externals, whilst the two-stroke flyers, the KX125 and KX250, get a few tweaks here and there to help keep them in vogue and up there with the best of them.
Basically a new bike in 2006, with a perimeter aluminium chassis, the Kawasaki boffins seem to have re-built the KX450F for 2007. A new five-speed box is the main change from last season's four-speeder, together with modifications to its Kayaba forks.
The KX250F receives comprehensive fine-tuning to its aluminium perimeter chassis and low to mid-range oomph in the motor, plus, its Showa suspension has also been re-vamped to give a better ride amongst a shed load of modifications that can only mean smiles on Kawasaki lovers' faces up and down the country.
T+MX sent its chief tester Johnno White and 2006 British Under 21 Champion Jim Murro to thrash all four models round a wet Tonymoto circuit in Hampshire recently.
KX125...
Jim Murro writes...
IT looks like Kawasaki has a really strong range right across the board for 2007, and I am sure it has a Youth 125cc class and Adult bike for you.
With not as much new technology thrown at Kawasaki's tiddler as its bigger brothers, the KX125 still sees tweaks to its motor that include tuning for better low to mid-range throttle control within the KIPS unit (Kawasaki Integrated Powervalve System).
It has a new ignition, carbon fibre reeds and new 'factory type' front and rear hubs and handlebar clamps with a cool brown finish, plus the new 2006 graphics.
I was more excited to get on the 125cc machine as it's been a long time since I threw my leg over a stroker and I enjoyed it... a lot.
I found it very nimble around the slick, tight track and used it to my advantage. There isn't too much to comment on with the 125 as there has been little or no change, the new graphics do make it look quite aggressive and eye-catching though and the nice, tight, narrow feeling whilst sitting onboard gives the rider confidence and it can be controlled and handled easily.
I was initially very surprised with the speed that could be carried around the track and that it is very easy to manoeuvre in tight corners and very willing to be flicked around in mid-air whilst jumping.
Power-wise, the bike felt a little rich off the bottom, but as long as you keep it on the boil it will perform just like most two-stroke 125 machines these days.
The brakes took everything I could throw at them and never let me down, which is always a good thing.
In the suspension department, if anything, it was a little too soft at the rear, but that could easily be remedied with a few adjustments.
All in all, the 125 is a great all-rounder and can be very competitive at high levels.
2007 KAWASAKI KX125 SPECIFICATIONS
ENGINE
Type: Liquid-cooled, two-stroke single with KIPS
Displacement: 124cm
Bore x stroke: 54.0 x 54.5mm
Compression ratio: 10.9:1 (low speed); 8.3:1 (high speed)
Valve/
Induction system: Six-petal carbon-fibre crankcase reed valve
Carburettor: Mikuni TMX38x
Ignition: Digital CDI
Starting: Primary kick
Transmission: Six-speed
CHASSIS
Type: Perimeter, high-tensile steel
SUSPENSION
Front: Kayaba 48 mm upside-down cartridge- type telescopic fork with 16-way com- pression and 16-way rebound damping
Rear: New Uni-Trak with adjustable preload, 16-way compression and 16-way rebound damping
TYRE/ WHEEL TRAVEL
Front: 80/100-21 51M/ 300mm
Rear: 100/90-19 57M/ 310mm
BRAKES
Front: Single semi-floating 250mm petal disc, dual-piston caliper
Rear: Single 240mm petal disc, single-piston caliper
DIMENSIONS
L x W x H: 2,165mm x 815mm x 1,265mm
Wheelbase: 1,470mm
Seat height: 945mm
Fuel capacity: 8.2ltrs
Dry weight: 87kg
KX250F...
Jim Murro writes...
AN absolute shed-load of changes and modifications have gone the KXF250's way for 2007, including revised aluminium perimeter chassis, to make it lighter and stronger, new suspension set-up with new springs and valves in the forks and shock on the outside and revised piston crown and looser fitting ring that Kawasaki says improve power and reduce mechanical losses through breakages internally.
New titanium intake valves for increased durability, a new carb and ignition settings and a longer and straighter air-box helps boost low-end performance.
A larger right-hand side radiator should help cooling efficiency and new, thicker gears will also help with durability.
The KXF250 also gets the new 'factory look' brown front and rear hubs, amongst other mods, including a petal disc and factory-type skid plate.
I already knew before I jumped onto the KXF250 it was going to be a good bike. You only have to look at its accomplishments over the last year or so, including what young star Tommy Searle has done with it, and you know there and then that it's no mug.
Along with checking out its improvements I was looking forward to jumping on and seeing what it can do on the track.
Within the first few laps the first thing I noticed was the awesome low-end power. Even while getting used to the bike I could tell it had a lot of torque.
Once I started to wind it on, the bike backed up my initial thoughts and even in the soft mud, after the downpour the night before, the bike coped with everything I could throw at it.
The excellent low-end power helps drive you out of soft and hard-packed corners at the twist of the throttle and a very strong mid range combined with an engine that still produces strong power at high revs that take you along fast, soft and hard straights, results in a very, very competitive bike.
The handling, as with the 125, was very good apart from the rear feeling like it squatted a little while initially getting on the power and on the take-off and landing from jumps, but that can be adjusted to suit individual riders.
It coped well with tight turns and soft-boggy turns, helped by good tyres.
The brakes once again couldn't be faulted. The 250F is a very competitive bike and with a few tweaks to suit rider preference could be raced at the highest level straight from the box and be up there at the sharp-end come the finish of a race, it's that good.
2007 KAWASAKI KX250F SPECIFICATIONS
ENGINE
Type: Liquid-cooled, DOHC four-stroke single
Displacement: 249cm
Bore x stroke: 77.0 x 53.6mm
Compression ratio: 13.5:1
Fuel supply/
Carburettor: Keihin FCR37
Ignition: Digital AC-CDI
Starting: Primary kick
Transmission: Five-speed
CHASSIS
Type: Perimeter, aluminium
SUSPENSION
Front: Kayaba 47mm upside-down twin-chamber telescopic fork with 16-way compression and 16-way rebound damping
Rear: New Uni-Trak with adjustable preload, dual-speed (low: 13-way, high: two- turns or more) compression damping and 17-way rebound damping
TYRE/ WHEEL TRAVEL
Front: 80/100-21 51M/ 315mm
Rear: 100/90-19 57M/ 310mm
BRAKES
Front: Single semi-floating 250 mm petal disc, dual-piston caliper
Rear: Single 240mm petal disc, single-piston caliper
DIMENSIONS
L x W x H: 2,160mm x 820mm x 1,270mm
Wheelbase: 1,469mm
Seat height: 960mm
Fuel capacity: 7.2ltrs
Dry weight: 92.5kg
KX450F...
JOHNNO WHITE writes...
IT IS unusual for a manufacturer to bring a completely new bike out one year and then almost rebuild it in the following year, but that is what it seems Kawasaki has done in 2007 with its 450 thumper.
For some reason I missed out on testing last year's range so I can only give you my opinion on the '07 bike without comparing it to the '06.
First Impressions of the bike are good although it did look like it was very wide and perhaps over-bulky on the rear fender and around the tank.
Like all new bikes now it comes with a good quality pair of 'bars, this one comes with Renthals and a factory looking set of petal discs that have a wavy look about them.
The front forks were the next things that caught my eye, obviously like most modern day motocross bikes they have a twin-chamber fork with 22-way compression adjusters and 20-way rebound, but the inner stansions of the fork are now coated in what Kawasaki calls DLC (diamond like coating), or what most of you will know it as nitriding like the GP boys.
Other changes that perhaps don't stand out as much because they are mainly internal are a revised intake port. The intake and exhaust valve timing have been changed to increase low down torque. A new flame arrestor is in the air box to improve intake efficiency.
The rear-shock has a revised rebound adjuster to improve damping; it works in conjunction with the modified aluminium perimeter frame which has improved spars to reduce its torsional ridgidity which will improve tuning and manoeuvrability.
One other major change is a five-speed box as opposed to the four-speed from last year. There are lots of minor changes too like modified grips and a brown factory finish on both the wheel hubs, different graphics and seat cover.
But, what did I think of the bike? My doubts about it being wide were soon forgotten because the riding position felt pretty good, the handlebars and seating felt very comfy although on some of the tighter parts of the circuit the tank still gave me the impression it was a tad wide. However the more laps I did the more I got used to it.
The power was very impressive, I found it very smooth but with a usable and aggressive feel to it. I found first and second gear a bit short but third, fourth and fifth were spot on and allowed me to attack the jumps with confidence.
I felt that the 450 pulled better if I rode it more aggressively and just hung onto the first three gears that bit longer. It was also a pleasure to throw around in the air.
Starting was easy enough from cold but when hot I had to use the hot start every time, although once or twice when I tried to start it in gear it wouldn't have it and I had to put in in neutral before it would kick into life.
The overall handling of the bike was very balanced and had a nice progressive feel to it. Usually the front-end on new bikes are a bit firm but the Kayaba forks on the KXF450 were spot on for me.
The track conditions were very muddy because of all the rain we had, so obviously there was a lot of long and deep ruts on the entrance and exit of most of the corners.
I found I could fire the bike in and out of the corners as if it was on rails. They also worked good on the big jumps both on take off and landing.
The rear-shock, if anything, was a tad too soft but I'm going to put this down to the bike carrying a lot of excess mud as opposed to bad settings (not excess body weight Johnno? Ed)
The brakes were spot on as always although solid discs would have been better.
2007 KAWASAKI KX450F SPECIFICATIONS
ENGINE
Type: Liquid-cooled, DOHC, four-stroke single
Displacement: 449cm
Bore x stroke: 96.0 x 62.1mm
Compression ratio: 12.0:1
Fuel supply/
Carburettor: Keihin FCR40
Ignition: Digital AC-CDI
Starting: Primary kick
Transmission: Four-speed
CHASSIS
Type: Perimeter, aluminium
SUSPENSION
Front: Kayaba 48mm upside-down AOS-type telescopic fork with 22-way compression and 20-way rebound damping
Rear: New Uni-Trak with adjustable preload, dual-speed (low: 22-way, high: two- turns or more) compression damping and 22-way rebound damping
TYRE/ WHEEL TRAVEL
Front: 90/100-21 57M/ 315mm
Rear: 120/80-19 63M/ 315mm
BRAKES
Front: Single semi-floating 250mm petal disc, dual-piston caliper
Rear: Single 240mm petal disc, single-piston caliper
DIMENSIONS
L x W x H: 2,185mm x 820mm x 1,280mm
Wheelbase: 1,485mm
Seat height: 965mm
Fuel capacity: 7.2ltrs
Dry weight: 99.8kg
KX250...
JOHNNO WHITE writes...
THE other bike I tested was the KX250 two-stroke, and like all Kawasaki's competitors it has not really changed much for 2007.
In fact, other than graphics and the two-tone seat cover, the only change is the handlebar clamps and the front and rear hubs, which now come with a factory brown finish.
The 250 also has petal shaped discs like the 450, works-style Renthals and an 'on the fly' adjuster on the clutch.
Out on the track, though, the 250 felt spot on. I found it was jetted perfectly for this supercross style track, obviously after getting off the 450 the 250 felt very lightweight and is definitely slimmer than its bigger brother and it's certainly easier to throw around.
The two-stroke 250 runs a high tensile steel perimeter frame where the KXF450 four-stroke runs an alloy one and is nearly 3kgs lighter (dry weight) than the 450.
The power delivery on the KX250 is really nice and smooth, but pulls from low down to the top end very quickly and in the deep ruts it tracked perfectly.
Riders won't need to fear power surges as it hits the power band and have their arms ripped out of their sockets as the power is so smooth as it comes in and therefore so controllable, the KIPS and K-TRIC (Kawasaki Throttle Responsive Ignition) work well together to get the power out quickly and smoothly.
With the solid five-speed box, which I found a bit clunky in certain parts of the track unless I was 100 per cent positive with selection, I managed to find a couple of false neutrals sometimes, it could have been down to the mud? I found I could short change the box which worked better from the corners to the jumps.
The Kayaba front forks and the Uni-trak rear-shock worked fine and had a good plush feel to it, but both worked hard to keep the bike tracking well.
The brakes, like all motocross bikes are fitted with these days, worked tremendously well and the front kit has a 250mm semi-floating petal disc, there is a 240mm petal disc at the rear too. Solid petal discs are available as an option for those wet races you 'sometimes' encounter and may work better in those conditions.
In general, a really good package in my opinion and still competitive with the 450 four-strokes.
The question is will the 250 two-stroke soon be a thing of the past or will manufacturers continue developing them? Hopefully they will be around for a few more years yet because they are so much fun to ride!
2007 KAWASAKI KX250 SPECIFICATIONS
ENGINE
Type: Liquid-cooled, two-stroke single with KIPS
Displacement: 249cm
Bore x stroke: 66.4 x 72.0mm
Compression ratio: 10.2:1 (low speed); 8.9:1 (high speed)
Valve/
Induction system: Four-petal carbon-fibre piston reed valve
Carburettor: Keihin PWK 38S
Ignition: Digital CDI
Starting: Primary kick
Transmission: Five-speed
CHASSIS
Type: Perimeter, high-tensile steel
SUSPENSION
Front: Kayaba 48mm upside-down AOS-type telescopic fork with 16-way compression and 16-way rebound damping
Rear: New Uni-Trak with adjustable preload, dual-speed (low: 18-way, high: two- turns) compression damping
TYRE/ WHEEL TRAVEL
Front: 80/100-21 51M/ 300mm
Rear: 110/90-19 62M/ 310mm
BRAKES
Front: Single semi-floating 250mm petal disc, dual-piston caliper
Rear: Single 240mm petal disc, single-piston caliper
DIMENSIONS
L x W x H: 2,185mm x 815mm x 1,265mm
Wheelbase: 1,480mm
Seat height: 965mm
Fuel capacity: 8.2 litres
Dry weight: 97kg
Specification: