With the success of the switch from the 250cc class to the four-stroke Moto2 formula - in terms of cost, and certainly in terms of grid size - the many fans of the two-stroke engine have been fearing the worst: the disappearance of the last two-stroke formula from the MotoGP paddock. At Assen, news is unofficially emerging that their fears have been confirmed. For the members of the Grand Prix commission are close to an agreement on replacing the 125cc class, and the bad news for two-stroke enthusiasts is that the smallest of the Grand Prix classes is about to turn four stroke.
From 2012 - or possibly 2013, according to some rumors - the 125s will be replaced with a 250cc four-stroke single. Contrary to earlier reports, though, the bikes will not be based on the existing four-stroke engines being used in motocross bikes such as Yamaha's YZ250F or Honda's CRF250R. The engines will have a maximum bore of 81 millimeters, making for much higher-revving short-stroke motors.
The risk of a four-stroke engine is that engineering costs can of course be radically more expensive, and so to keep down costs, two measures will be put in place. Firstly, any manufacturer wishing to enter will have to make a significant number of engines available, with between 10 and 15 the figures being mentioned. Secondly, the engines will be offered at a fixed price of around 10,000 euros, in the hope of discouraging factories from investing large sums to try to gain an advantage.
Given that the current range of motocross 250s produce in the region of 45 rear-wheel horsepower with a narrower bore and much longer stroke, the new "Moto3" bikes are likely to produce something in the region of 50 horsepower, not a million miles from what a racing 125cc bike produces. What that means in terms of speed remains to be seen, as the additional weight of a four-stroke lump will likely be a disadvantage.
The astute observer will have noticed that the 81mm bore is a familiar number. With the new 1000cc regulations due to be introduced in 2012 also imposing a bore limit of 81mm, a 250cc single would be one cylinder from the new 1000cc bikes. What this means for Moto2 is potentially even more interesting: With FIM President Vito Ippolito already talking of removing the spec engine requirement for Moto2 at the end of the three-year contract which Honda has, the natural progression from this - as veteran journalist Dennis Noyes pointed out - is a 500cc twin with an 81mm bore. Such a machine would be much closer to a Grand Prix prototype than the current production-based 600cc four cylinder engine being used in Moto2.
Speculation about Moto2 must remain just that, however, speculation. But that the 125cc formula is coming to an end is virtually certain. From 2013, the only two-strokes in the paddock will be the scooters carrying the riders to and from the pits.
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