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Generation comparison: lightweight motorcycles

Lightweight bikes in comparison

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A man builds a dream. Rudiger Kranz is a lightweight construction freak and was in the German Supermoto professional league until the end of 2009. So it’s not surprising that he used a 450cc motocrosser to build his first road racer. PS editor Robert Gluck drove the racing flea and for comparison a 1993 Yamaha TZR 250 RSP.

Nurburgring, paddock of the GP track. The participants of the PS-Racecamp are battered by bad weather. It is raining, and if you don’t just put rain tires on your racing car, you are besieging the coffee machine and waiting for improvement. When the PS testers unload the ghost of the past in the form of a rare Yamaha TZR 250 RSP, never officially sold in Germany, and the ghost of the future, the 450mototechGP, not only the faces of some attentive observers light up, but also the sky.

E.t is unbelievable what a magnetic effect a two-stroke still has on its surroundings today. A handful of enthusiasts are immediately there, asking about the year of construction, weight and performance. Marvel at the compactness of the racer.

Even more interest is drawn to this incredibly slim, very delicate thing that is placed right next to it. Stealth design in white, hardly wider than a beer bench and also not much heavier, like at feather-light, inflated pocket bike on its aluminum stands. The pointed nose, the clear, deliberately angular tank hood and the angular rear end give the 450mototechGP, as its official, somewhat bulky name, a Moto2-like appearance. The mighty wheels also play a major role in this – a 3.50 x 16.5 is in the front" large PVM forged rim, a 5.00 x 17 at the rear" large wheel in the chassis of the Ex-Crosser. The TZR 250 with its narrow, conventional 17-inch models looks almost staid.


The Yamaha TZR 250 RSP from 1993.

Booooaaaaaaaaah !!! The Yamaha saws out of the Coca-Cola curve onto the start-finish straight. The little white pointer greedily snaps at the filigree numbers on the tachometer display. Like a Pacman on speed, he nibbles on 9, 10, 11 and 12. This is followed by fourth gear. 9, 10, 11, 12 – booaaah! Fifth gear: 9, 10, 11, 12 – boooaaah! Sixth gear: 9, 10, booaah 11, boooaaah, the 12 is a long time coming. The TZR is perfectly translated for the Nurburgring, the Pacman pointer grabs the small 12 after the start-finish line and turns briefly into the red area until the braking point. Off into the blocks! As a four-finger brakeman who has been on the road a lot lately on thousands of super sports bikes, I pull the brake lever as usual. The rear of the TZR rises immediately, easily controllable, yet surprising. I can’t go any further with my butt, the rump severely restricts the work place for gymnastics. Didn’t Dominik Klein (www.yamaha-klein.de), who gave us this exclusive burner, say something about new brake pads? A force that bites into the two thin 282 millimeter slices!

The close right in the "Haug hook" it is time to put down with a lot of speed and cock the tap again. "Booo!" it scolds from the engine room. Damn! I’m in third gear instead of second, the little Pacman on the tachometer is lazy lounging around seven, it seems as if it has stopped "Insert Coin" on the display. The second slips effortlessly into his workplace, which Yamaha celebrates: 9, 10, 11, and the 12! Yes, the saw is sawing again, the long left curve is quickly rushed through, while the BT 090 from Bridgestone bite into the asphalt at a steep incline. The wide curve is nasty, becomes a very tight left turn. The braking waves of Formula 1 cars make the Yamaha difficult. The seventeen year old dampers are fully adjustable, but their basic setting is far too soft. That doesn’t change anything about this butterfly-like turning behavior, but it prevents you from building up the cornering speed necessary to nail the corners with real pepper. And that’s exactly what makes two-stroke driving unique. This brutal entry speed, which is then taken with a high incline in a round arc to the exit of the curve.

Unique? Yes, but not critically endangered like the two-stroke engines. Because it is not the motorization that allows this style of driving, but the vehicle mass, or the total mass of the combination of driver and motorcycle. And the enjoyment of this driving experience is also possible with four-stroke engines, as long as their mass is small enough.


The self-made hit from Mototech: 450 Mototech GP.

Rudiger Kranz from Denkendorf (www.mototech.de) never drove a 250cc two-stroke on the asphalt, but after the end of his active Supermoto career he subconsciously dedicated himself to this feeling. The 600 he borrowed for race training was far too heavy for him, and the turning behavior was too indirect and too slow. Buying a saw didn’t come in the bag, so you had to have your own. The suspension tuner and setup specialist caught the eye of the 450cc motocross. If you can turn a crosser into a supermoto, then you have to be able to turn it into a street car, so the thought.

Thought and done, the Suzuki RMZ was meticulously measured and the chassis data compared with that of modern super sports cars. Then Kranz tried the wrench, lathe and milling machine, went to his friend at IMM-GmbH and built the entire cladding with him. Then he screwed on the wheels and brakes, the engine got a cylinder head machining and thus breathed in its 63 hp. The meticulous tuning of the shortened motocross suspension elements followed. The worst was done. The geometry of the 450mototechGP chassis is based on the data of the KTM RC 8, but its dry weight of one hundred kilograms is far below that, despite the heavy fairing and the heavy stainless steel exhaust. With a little carbon and titanium, another five kilograms could easily be saved.

But is that necessary? The 450 will also accommodate tall riders and also offers enough space for long legs. The very narrow cladding protects the pilot very effectively, the recess in the tank lid perfectly accommodates the chin area of ​​the helmet.

Folded in this way, it goes full Lotte downhill towards the Dunlop hairpin. The little white girl flies with a dull thud through the fast arcs, can be steered with the blink of an eye even at high speed, flies with a large excess of the already braking 1000cc superbikes towards the bend. The procedure for every late braking attack follows. Lightning-fast straightening of the upper body, accelerating, pulling the brake and clutch, shifting into third gear, engaging, shifting, applying the gas, burning with a lot of momentum to the apex and then opening the throttle valve again full pipe.


It couldn’t be more manageable: These two racing fleas practically carry themselves through the curves on their own.

It takes days for this process to be smoothly and effectively trained. Because the 450mototechGP is like a fascinating fairy tale mirror. You look inside him and he shows you all your inadequacies. Radically shows you the bitter truth of your humble racing skills. Every 1000, even a 600, somehow conceals driving errors such as turning too early, braking too early, accelerating too late or even a too casual posture somehow with its power. However, if you want to have maximum fun on the race with 63 hp, you have to drive super clean and to the point, you have to take every ounce of momentum with you. That is admittedly exhausting because it is only possible with a very high level of concentration and discipline, but to be honest, it is the high school of motorcycling. As in any sport, effort is also rewarded. There is definitely nothing sweeter than a clean lap on this driving machine. She chisels the grin permanently on your face. It was never possible (but also necessary) to give full throttle so early and safely as on this little whirlwind. Since the Bridgestone slicks are designed for significantly more power, the switch on the Mototech can be flipped without any worries, the lean angle can be increased again and the cornering speed gradually increased.

Rudiger’s 450 can be called at "Driving school motorcycle" are designated. A 15-year-old beginner will get along better with it than with a bitchy 125cc. In terms of cornering speed, handling and lean angle, the experienced pilot moves into spheres with the 450 that were previously denied to him.

The best thing about the whole story: The Mototech concept is cheap and brand-independent. Kranz converted a Suzuki because it was standing there. The conversion is possible with all makes, at a similar price. A budget version without a radial brake system can be obtained when purchasing a new vehicle for 6500 euros for less than 10,000 euros. A new Suzuki RM-Z 450 from 2006 is currently available on the Internet for 4500 euros. Anyone who shoots such an offer can easily treat themselves to the good radial brake system. So is it time to sell the thousands and learn the true art of racing? It is definitely worth serious consideration.

Conclusion: If the two-stroke engines have to die, then at least replace them with 450 singles. They drive as precisely but not as toxic as a 250 saw and generate a very similar driving experience. The driving fun comes from the cornering speed and the outstanding handling. My dream: KTM has Rudiger Kranz build 30 racers on a 450cc basis and thus advertise a cup with no age limit. The starting field would be full and I would be there. And I would also buy a street version of the Racer that was offered later!

Yamaha TZR 250 RSP


In the 1990s, the TZR 250 RSP brought racing technology to the streets. Pure racing thanks to 126 kg and 80 hp.

Two-cylinder 90 degree V two-stroke engine, 59 kW (80 PS) at 12,000 rpm, 48 Nm at 10 550 rpm, 249 cm3, bore / stroke: 56.0 / 50.7 mm, compression: 8.5: 1, 2x Mikuni flat slide carburetors, 32 mm throttle valves (oval), mechanically operated multi-disc dry clutch, six-speed gearbox, chain

landing gear:
Light metal bridge frame, steering head angle: 66.0 degrees, caster: 90 mm, wheelbase: 1340 mm, inner fork tube Ø: 41 mm, spring travel from / h .: 125/120 mm

Wheels and brakes:
Light alloy cast wheels, 3.00 x 17"/4.50 x 17", Front tires: 110/70 ZR 17, rear: 160/60 ZR 17, 282 mm double disc brake with four-piston fixed calipers at the front, 210 mm single disc brake with two-piston fixed caliper at the rear

Weight (dry, v / h)
: 126 kg * (50.1% / 49.9%), tank capacity: 14.5 liters of super

Base price: approx. 17,000 D-Mark (1993)

Mototech 450 Mototech GP


Even without a fairing, the Mototech looks tidy. No frills on the bike – what’s on it has to be on it.

Single-cylinder four-stroke engine, 4 valves / cylinder, 45.5 kW (62 HP) at 8900 / min, 53 Nm at 7100 / min, 449 cm3, bore / stroke: 96.0 / 62.1 mm, compression: 12, 8: 1 , ignition / injection system, 43 mm throttle valves, mechanically operated Rekluse multi-disc oil bath clutch, five-speed gearbox, chain

landing gear:
Light metal bridge frame, steering head angle: 66.3 degrees, caster: 100 mm, wheelbase: 1420 mm, inner fork tube Ø: 47 mm, spring travel from / h .: 150/150 mm

Wheels and brakes:
Forged alloy wheels, 3.50 x 16.5"/5.00 x 17", Front tires: 125/600 R 16.5, rear: 165/630 R 17, 320 mm double disc brakes with radially attached four-piston fixed calipers at the front, 240 mm single disc brakes with single-piston floating calipers at the rear

Weight (dry, front / back): 100 kg * 49.1% / 50.9% Tank capacity: 6.5 liters of super

Base price: 10 999 euros


Robert Gluck: PS test.

Racing should become cheaper. That’s why the 250 two-stroke engines died, that’s why the 125 two-stroke engines will go under. Foolishly, however, the small circular saws are to be replaced by 250cc four-stroke engines. Incomprehensible because the small single cylinder cannot hold a candle to the 450 single in many ways. Here is just one example: the maintenance costs. A 250cc four-stroke in Supermoto mode should be revised every 25 hours of operation. The service life of a 450 engine is almost four times as long with the same load. These intervals will be shortened again on the circuit. Just double the number of revisions will significantly increase the operating costs of a 250 compared to a 450 engine. So if it were about sport and a reduction in costs, the 450 singles would logically have to migrate to a Moto3 chassis. But according to Dorna, they don’t. Another toad in life that you have to swallow without understanding it.

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