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Motorrad presents: Honda CRM 250 AR

Radical cure

With the AR (Active Radical) concept, implemented as standard in the CRM 250 Enduro, Honda wants to convert the two-stroke engine from polluting the environment to a clean man without depriving it of its virtues.

Apart from light motorcycles and 50s, two-stroke engines have largely disappeared from the streets due to bad environmental mores, and even in the off-road area, their last refuge, they are now bothered by them.
In this situation, of all things, four-stroke traditionalist Honda is fighting the seemingly inevitable and is presenting a new approach to the two-stroke issue with the AR engine.
The AR principle tries to turn the weaknesses of the two-stroke engine for the better. These weaknesses – high consumption and poor exhaust gas behavior – result from the fact that – to put it simply – unused fuel can escape through the exhaust. Particularly in the lower speed range, the sluggish combustion processes result in incomplete use of the available chemical energy: there are residual amounts, so-called radicals. The trick of the AR system is to steer the willingness of these molecular fragments to bind in beneficial ways. If you whisk it in the cylinder with a suitably composed fresh gas, the whole thing burns spontaneously and largely without leaving any residues – without any intervention from the spark plug.
A flap in the exhaust leaflet acts as a whisk, which brings residual and fresh gas into intimate connection, the position of which is determined by the central computer from numerous parameters – throttle valve position, speed, cooling water and cylinder head temperature, negative pressure in the intake tract. It is supported by an electronically controlled carburetor, which is supposed to ensure the right mixture composition at every operating point of the engine.
Beyond the complex electronics, the AR single-cylinder is a two-stroke engine in the best sense of the word: mechanically simple, compact, light. And willing to perform: 40 HP at 8000 rpm and 39 Nm at 6500 rpm are not record-breaking, but very honorable. These values ​​pale in view of the realized "side effects": The AR engine should emit 50 percent fewer unburned hydrocarbons than conventional two-stroke engines and, in terms of CO and nitrogen oxide emissions, even clearly undercut representatives of the four-stroke principle. One can hardly wonder about the promised consumption figures: 3.4 liters per 100 kilometers at 120 km / h and seven liters at full load.
It has not yet been possible to verify whether these promises will be kept. How the CRM drives, on the other hand, does: Honda Austria has imported four of these motorcycles and given them for test driving.
The AR single initially makes no fuss about its special position. It comes to life after a relaxed step on the kickstarter and rattles along well-muffled in the style of any two-stroke engine. But as soon as you drive off, the aha-experience comes: Without a lot of speed and without magic with the left hand, the CRM comes out of the starting blocks. Slightly increased idle speed, clutch in, and off you go – every beginner can do it right away.
Towards top performance, the 250 seems a bit tough. This may be due to the subtle background noise, or – what is more likely – the steady development of power. This is registered with a happy surprise when the machine is to be accelerated out of bends without downshifting x times: In the best four-stroke manner, one turn of the throttle is enough to let the CRM scrape vigorously with the tires – without stuttering, without hesitation. The effectiveness of the AR process can be checked with astonishing results by pressing the kill switch: the engine actually runs up to about 5000 rpm with the ignition switched off.
No wonder that the spark leaps over with the driver too, after all VS.Thanks to the high-torque motor, low weight and handy chassis, the RM 250 AR is a user-friendly broadband enduro that cuts just as good a figure in demanding terrain as it does in everyday use. It’s just a shame that this motorcycle is neither available for money nor for good words in Germany. The fact that the AR principle in the form of the 125 Pantheon scooter is coming to our streets is little consolation.

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