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Cyclone 4-Stroke 450SX KTM Superkart

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Is 250 National short circuit racing in decline? Discuss!

No new engines have been accepted into the class for 2007.  The most popular engine, the Honda CR250, is a five year old design, the alternative Rotax motor has not been made for almost a decade.  Its twin cylinder brethren has already disappeared from short circuit.  So how long can the 250 Nats continue? Two men that think they have the answer are Paul Whiting and Richard Cornick.  “The original concept of 250 National was to take a readily available motocross engine and now the manufacturers are stopping making 2-strokes we looked at the costs and availability of the various 4-stroke replacements.  We have picked the KTM 450SX,” said Whiting, who has bank-rolled this project.  Whiting, who used to drive 250 National karts and was third in the Dunkeswell club championship, has teamed up with Cyclone kart manufacturer Richard Cornick to build this prototype muscle kart replacement for 250 National.   They have had the KTM modified for five gears, and added an electric self-start.  “We’re trying to generate a user friendly outfit comparable with and designed to run with the current class, but we are not trying to replace that, merely have an alternative with a similar concept,” Whiting added.   They felt that by adding the TAG (Touch and Go) electric start it would help to attract drivers from other classes that are already TAG, and make the dummy and starting grid a safer place to be.  As said, the chosen KTM motor is a 450cc 4-valve single cylinder overhead camshaft 4-stroke, delivering between 55 and 60 bhp with immense torque.  It will rev up to 10,000 rpm but this is an area that shouldn’t need to be explored.  The engine weighs some 5 to 8 kg more than a CR250 and it is hoped to sell it for something in the region of £3,000.  The engine life between rebuilds will of course be much extended over a 2-stroke.  As a matter of fact the kart on test weighed 123kg.  The engine is nicely packaged, and not too tall.  It sits far enough forward on the Cyclone so that the cylinder does not get in the way of flailing elbows.  A new homologation type CIK airbox adds to the karting image.

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So what was it like to drive?  I was lucky to be given a chance to try it round Shenington.  Sitting in it for the first time I pulled out the stop switch and pressed the tiny start button mounted on the steering wheel.  The engine turned over but failed to start.  A little more throttle, a second try and it burst into life, settling into a steady tickover, sending vibrations through the kart which of course were not noticeable at all once underway.  As I checked the brakes on the way out of the dummy grid, I found very little travel, and a very positive deceleration.  Pushing the left handed gearstick forward to go up the gears I was on my way down to the Stratford hairpin.  Like a 250 National, the up-changes come fast, and it was all too easy to hit the rev-limiter, but it is not such a frenetic experience as an ICC 125cc gearbox kart.  Make no mistake, this kart is a seriously fast piece of machinery, yet user friendly enough for the relative novice to drive round.  There is no doubt it could be hitting speeds of nearly 100 mph on a short circuit like this.  As I tried to settle into a rhythm, down two gears for the Bruno chicane, and down three for the two hairpins, I found it would accelerate smoothly whilst sticking to the road like glue on the way out, then progressively sliding out a little further on full power.  There was none of the difficulty I have had with a 250 National kart when the motor suddenly comes on song and the back end bounces almost uncontrollably in the hands of a novice. 

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Perhaps it would be better to leave it in the hands of an expert, and one was right on hand in the shape of 250 expert Don Kennedy, who was himself once an accomplished motocross rider.  After a few suggestions and improvements Kennedy took the lap time down to 47.8 seconds, compared with the previous club race quickest of 47.2s albeit on a slower track than normal, after track re-surfacing.  Usually the 250 Nationals would be in the 45 second bracket.  “It felt really easy to drive but you have to get the down-changes just right, it has so much compression it is easy to lock up the brakes.  The engine has so much torque you would be able to go round just using two gears, it just pulls and pulls,” enthused Kennedy.  Multiple 250 National champion Mark Allen was an interested spectator, and said: “I think it has got a little way to go before the current drivers will come off their 2-strokes, but I see no reason why they couldn’t run off the back of a 250 National grid using the same tyres.” 

And that is Whiting and Cornick’s aim.  Their next step is to put draft regulations into the MSA to try and have it accepted with maybe a special waiver to allow the prototype to be raced somewhere just as an experiment.  “We need to address the noise issue first, we have some new silencers coming and it is our goal to make the kart quieter than a current 250 2 stroke. We see this as the only way forward and is indeed a very pertinent issue for many clubs and circuits around the country,” said Whiting.  It’s always hard to introduce new classes, but this one certainly deserves a chance and with a bit of luck could be the saviour for the big gearbox brigade.