IN the essentially two-stroke world of motocross there have always been four-stroke bikes. In recent years there have been four-strokes that have made an increasingly convincing case that now is the time to abandon your stinkwheel for ever. And now, with the launch of the Honda CRF450R, there is a four-stroke that tries so hard to offer the best features of both two and four-stroke that a steady flow of converts to the way of the thumper might just start to become a torrent.
After a first ride on the CRF, it’s clear it has most of the virtues of each type of bike with few of the vices that supporters of either opposing faction might complain about. Imagine a typical exchange…
Tommy Two-stroke: " Even the latest ‘new generation’ four-strokes are a bit heavier and don’t turn quite as quickly. They’re harder to start, especially if you fall and they flood. And I just don’t get on with all that engine braking. "
Freddie Four-stroke: " Yeah, but you can get the power down with much less drama, you don’t have to mess around with gearchanges nearly as much because of the torque, and I like the engine braking – all these things let me concentrate more on riding fast. "
The CRF brings these two camps closer together by offering:
* An engine that revs high and free like a stroker but still gives predictable, solid drive and can be ridden using many fewer gearchanges
* Weight and manoeuvrability that is so close to a two-stroke, it’s hard to tell the difference (at 102kg it is 4kg more than Honda’s equivalent 250, and up to 5kg less than four-stroke rivals)
* Low engine braking that means either type of rider can easily adapt their braking style
* The best aspects of existing four-stroke starting gizmos – an auto decompressor on the kickstart makes it easy to kick over, and a bar-mounted hot start lever makes starting a flooded motor a breeze.
In more detail, this is how it’s been done….
To create the motor for the firm’s first four-stroke crosser, Honda’s designers came over all old school, with a " back to basics " approach. But that doesn’t mean it’s hard to start and leaks oil. That means a review of mechanics to create a lightweight and powerful engine.
At just 29.7kg the innovative single cam engine is certainly light, while the 55bhp at 9000rpm and 36ftlb of torque at 7000 will put it up with the best. Honda claims the 449cc capacity was the natural result of the best design it could develop. Nothing to do with new GP rules that will soon allow four-strokes up to 450cc to race in the 250 class, then?
The low weight and strong power make the CRF surprisingly quick. Strokers generally give you good acceleration so long as you’re prepared to open the throttle fast and hard – there’s not a lot in the bottom end so you head straight to peak revs. The problem is, the less your skill and experience, the more wheelspin and rider fatigue you suffer. The CRF450R, like the Yamaha YZF426 and KTM 520SX offers an alternative of smooth, controlled drive.
There’s excellent throttle response, the motor spinning up to a vertiginous 11,300rpm with a quick twist of the wrist. However, as with any of the new generation four stroke bikes, you can take advantage of a much broader powerband to gain speed quickly and smoothly without having to go this high.
Not only does it offer a good spread of power, it also lets you use all of it. With a flat torque curve, you can easily get the power down on loose ground. The result – you go into fast-forward rather than just obscuring the background with dirt from a spinning rear wheel.
On the way into corners, there is enough engine braking to make balancing front and rear brakes an easier task, yet the bike can also be backed-in, turned tight and fired out using the motor’s instantly-available power.
Tight turns are where four-strokes often suffer – performing better round momentum-carrying wide lines – but the CRF can do tight as well as wide. As part of its review of engine design, Honda looked at items like the camshafts and camchain. Traditionally, these are quite heavy and that rotating mass affects how the bike turns – it’s like having a gyroscope in the frame. With ultra-lightweight components, not only does the engine rev quickly but it allows the bike to turn better. Overall, the feeling is much more like a light two-stroke than a less wieldy four-stroke.
Though the CRF450R is marginally heavier than the CR250R, you don’t feel it. The light weight and Showa suspension derived from the 125/250 CR-series handles the extra weight well thanks to slightly uprated springs. The frame is an adaptation of the highly successful twin-spar aluminium frame from the CR series.
Honda has delayed its entry into this market currently dominated by earlier-movers Yamaha and KTM. But it’s been worth the wait because the CRF looks like the best attempt yet at a four-stroke that can be ridden fast by almost any kind of rider – clubman or GP rider, two-stroke or four-stroke fan, whatever their preferred riding style.
Of course, as with any bike that sets out to please two different groups of rider, it might just as easily end up pleasing neither of them as much as both. For once, our two opposing parties might agree on something…
Freddy Four-stroke: " Yeah, I rode one of them CRFs last week – the engine braking is rubbish and you still need to change gear more often than my KTM. "
Tommy Two-stroke: " Yeah, so did I – the engine inertia made the nose dip more over jumps than my CR250 and I still can’t get it re-started quite as quick. "
One thing’s for sure –if CRFs start winning races, there’ll soon be a few more riders from both camps re-examining their prejudices…