Double impact from Suzuki - RM-Z250 and RM-Z450
By TMX Archives on 9th Nov 06
SUZUKI had been left behind a bit over the last couple of years in terms of 250cc four-stroke technology. Its first attempt was a joint venture with Kawasaki in 2004 and for the last two years it has left the machines alone.
For the forthcoming season, however, Suzuki has definitely pushed the boat out with a completely new bike - the all-new RM-Z250 K7.
A lot of the design ideas have come from its big brother, the RM-Z450, which has won various championships over the last two years.
The RM-Z450 hasn't been forgotten about though as the Suzuki technical bods worked their magic on the quarter-litre thumper, with frame, internal and plastic tweakings going on - all for the better for 2007.
But, it's the RM-Z250 that will have all eyes on it as it comes into a very competitive class.
With light-weight and very strong aluminium frame, revised five-speed box, new swingarm with newly designed suspension linkage, tweaked Showa suspension units, redesigned internals for the motor and bigger radiators for better cooling, all goes to make, what could be, a cracking 'weapon of choice' says Suzuki.
T+MX chief motocross tester Johnno White took the trip to the German GP track at Teutschental for the launch of the new bike and its bigger brother the RM-Z450, read on.
RM-Z250 K7
THE main question was surely going to be, is the Suzuki RM-Z250 K7 going to be just as mega as it's original offering in previous years?
At first glance you think it looks just like the RM-Z450, but when you study it you realise that the tank and rad shrouds are a totally different shape, the seat is different and so are the side-panels and rear fender.
The frame looks like the 450's but is a lot smaller and slimmer, the new seat and tank have given it a much nicer riding position than the previous model, even the fork guards are a different shape. The triple clamps have been re-designed for the new chassis and are complimented with Renthal Fat 'Bars.
The radiators are larger which results in higher cooling and better performance, the Showa shock and forks are pretty similar to the 450 ones but obviously valved and sprung lighter.
Like I mentioned earlier the ally frame is completely new and although it looks the same it is actually 1.1kgs lighter than the steel frame of last year.
So, onto the engine which is also brand new and comes with modifications to the combustion chamber, port shapes and cams to increase mid to high range performance.
The gear ratios have been changed with third to fifth being brought closer for more comfy shifting. One major improvement is the oil strainer, you can now take out the metal gauzed strainer without pulling the engine apart, it is now just a matter of undoing a bolt on the side of the engine and pulling it out.
The gear selector mechanism has been changed to improve changing gear and make it much smoother. The water pump is a brand new design for higher cooling performance, or in other words, to stop it from overheating.
Along with modified lightweight valves and lightweight springs to help maintain precise valve control at high RPM and a modified cylinder, it is pretty obvious Suzuki means business for 2007, so although the bike looked the dogs, how did it go?
Within two laps I felt right at home on the new RM-Z250, the new seating position, tank and rad scoops give it a real slim feel and makes it effortless to move around on.
I was very impressed with the Showa suspension, which if anything, was a little bit soft for me.
However, Suzuki has definitely aimed this bike towards the lighter rider because it had the nice plush feel that a bike with re-valved suspension feels like, the softness didn't hinder me one bit, if anything it made me feel very confident in the corners because I could attack them with confidence.
I found that once I got the front-end into a rut I could roll the throttle on straight away knowing full well that the back end would just follow through without any problems.
Over jumps the new bike was mega-light to flick around and I found the new aluminium chassis layout 100 per cent improvement on last year's bike.
The bend of the Renthal 'bars was okay, but, probably not as high as I would prefer. The tyres were perfect for the track conditions because it was rock hard and the RM-Z250 comes with Dunlop hard-pack tyres, but for the UK I don't think they are the best choice, especially for this time of year.
The power of the new motor is also a major improvement on last year's bike, which, I have to be brutally honest and say that I didn't feel that the motor was that quick, especially compared to the YZ and CR, but this year's engine is definitely on a par if not probably a bit quicker than the other Japanese offerings.
The five-speed gear ratios seem a bit weird at first but once you get used to them it makes it a lot easier to ride.
I found that I only really used third, fourth, and fifth and sometimes I could land off a tabletop in fifth and, because the track was so fast, I could roll the power on and it would hook up real quick almost like a 450, where on the previous bike you would definitely have to down shift once or even twice.
The brakes and gearbox worked fine all day and the new selector mechanism gives selection a lovely smooth, yet firm feel. Jetting was perfect and starting the bike was fine both hot and cold.
Suzuki has thrown down the gauntlet with this bike and I expect you will all see a lot of these around your paddocks next year.
RM-Z450K7
ONE could be forgiven for thinking that the 450 K7 would have definitely been left alone with all the time and money going into developing its little brother, but it too has undergone some major changes for 2007.
It first came out in 2005 and then, for 2006, had some minor changes which, in my opinion, they were changes for the worst.
The 2005 model was mega, lovely, strong usable power like all 450s should be, but in 2006 the power was more revvy and harder to ride, so, for 2007 Suzuki has gone back to the drawing board and although it is quicker than ever, the actual delivery is almost identical to the 2005 model.
The ally chassis has been slimmed down similar to the RM-Z250 and the side panels and rad cowls have been re-designed to get more air in the air box and more air around the rads.
The 450 comes with Bridgestone tyres which I find a bit weird seeing that the RM-Z250 has Dunlops. The 450 has also had modifications to the crankcases so you can take out and clean the gauze filter strainer without stripping the engine, plus, it also comes with an automatic cam chain tensioner which has replaced the manual one of the previous two years.
The Showa suspension comes with different settings and the quieter exhaust conforms with US standards, which can only be a good thing.
On the track it felt like a rocket at first because I had just got off the RM-Z250, but on my second session I got used to it and started to put in some quick laps.
The available torque on the new 450 is awesome, I thought it might have come with five gears like Kawasaki's KX450F but the yellow perils have stayed with the four-speed box.
In all honesty, the RM-Z450 does not need an extra gear, it is just so very fast with four already, so I only used the top two gears, but because of the grunt of the RM-Z450 this was not a problem and it is still very controllable over most terrain.
The Showa suspension felt pretty good too, therefore I found the bike easy to track and throw around. Once or twice I over-cooked a few corners, but I think this was because I kept getting caught-out with the all-encompassing speed of the bike.
It seems that 450s are getting quicker and quicker and before long they are going to be like 500 two-stokes of yesteryear.
All in all, a mega 450, and if you think you're big enough, go and book a test ride on one.
2007 Suzuki RM-Z250 SPECIFICATIONS
Engine
Type: Liquid cooled DOHC four-stroke single.
Capacity: 249cc.
Bore: 77.0 x 53.6 mm.
Compression Ratio: 13.4:1.
Lubrication: Suzuki Advanced Sump System
Ignition: Digital AC-CDI.
Fuel System: Keihin FCR 37.
Transmission: 5-speed, constant mesh.
Drive: Chain.
Chassis
Frame: Aluminium.
Front Suspension: Showa 47mm telescopic,
pneumatic forks/ coil spring, oil damped.
Rear Suspension: Swingarm, link type, Showa
piggyback-reservoir shock.
Front Brakes: Disc.
Rear Brakes: Disc.
Front Tyres: 80/100-21".
Rear Tyres: 100/90-19".
Dimensions And Weights
Overall Length: 2165mm (85.2in).
Overall Width: 830mm (32.7in).
Overall Height: 1260mm (49.6in).
Wheelbase: 1465mm (57.7in).
Seat Height: 955mm (37.6in).
Dry Mass: 92kg (202.8lbs).
Fuel Capacity: 7.5litres (1.6gallons).
2007 Suzuki RM-Z450 SPECIFICATIONS
Engine
Type: Liquid cooled DOHC four-stroke single.
Capacity: 449cc.
Bore: 95.5 x 62.8mm.
Compression Ratio: 11.9 : 1.
Lubrication: Suzuki Advanced Sump System.
Ignition: Digital AC-CDI.
Fuel system: Keihin FCR 40 MX.
Transmission: Four-speed, constant mesh.
Drive: Chain.
Chassis
Frame: Aluminium.
Front Suspension: Showa 47mm telescopic,
pneumatic/ coil spring, oil damped.
Rear Suspension: Swingarm, link type, Showa
piggyback-resevoir shock.
Front Brakes: Disc brake.
Rear Brakes: Disc brake.
Front Tyres: 90/100-21".
Rear Tyres: 120/80-19".
Dimensions And Weights
Overall Length: 2185mm (86in).
Overall Width: 830mm (32.7in).
Overall Height: 1260mm (49.6in).
Wheelbase: 1480mm (58.3in).
Seat Height: 955mm (37.6in).
Dry Mass: 100kg (220.5lbs).
Fuel Capacity: 7 litres (1.5gallons).
Specification:
