After some years of rumours, ammendments to the Technical Regulations governing Grand Prix Motorcycle Roadracing were released on the 8th April 2000 opening the way for competitive four-strokes to rejoin the premier 500cc (GP1) class. The move is the first step in phasing out the increasingly irrelevant two-strokes that dominate racing today. The last four-stroke to race in Grands Prix was the Honda NR500 introduced in 1979- a unique oval piston V4, and the last four-stroke to win a race was an MV Agusta at the old Nurburgring in 1976.

The new rules to be introduced for the 2002 season state:

For 2-stroke engines only, the fuel tank capacity will be limited to 32 litres maximum.
4-stroke prototype motorcycles will be experimentally allowed in the FIM Road Racing World Championship Grand Prix, with the following characteristics:

1. Engine displacement: maximum 990cc, regardless of the number of cylinders
2. Minimum weight:

• 3 cylinders 135 kg
• 3 'cylinders' (oval pistons) 145 kg
• 4 cylinders 145 kg
• 4 'cylinders' (oval pistons) 155 kg
• 4 or more cylinders 155 kg

3. Fuel Tank capacity: maximum 24 litres for 2002, maximum 22 litres thereafter
4. Noise limit: pre-race limit: 115 dB/A post-race limit: 120 dB/A
5. All the rest as per the current regulations, the major points of which are:

• Capacity of 350cc to 500cc
• Maximum of 4 cylinders (two-stroke only)
• No supercharging
• Maximum of 6 speed transmission
• Weight limits: 4cyl- 135 kg, 3cyl- 115 kg, 2 or 1 cyl- 100kg (two-strokes only)
• Number of cylinders is determined by the number of
  combustion chambers ( not pistons ) - if linked chambers -
  the passage must be 50% area of the inlet port area.
• If motor & chassis are by different manufacturers - both names
  must appear on the bike.
• Titanium is not allowed for forks, frame or swingarm
• Aluminium or titanium is not allowed for axles
• Maximum rear rim width 6.25", minimum rim dia. 400mm.
• Front guard minimum 100° of wheel circumference
• Rear guard minimum120° but 180 deg of rear wheel must be visible
• Fairing- no more than 100mm past front axle line or past
  back edge of rear tyre. Rider must be completely visible
  from the side and above the bike. Back of seat must be less
  than 100mm high. Seat width 450mm max.

FIM President Francesco Zerbi said: "It is a very important day for our sport. The philosophy of this new agreement is to clearly state that production motorcycles cannot be transformed in order for them to take part in the Grand Prix events that are restricted to prototype bikes. I think that adaptation to modern technology is a very important step forward in the progress of motorcycling and for our sport."

Why 990cc?

As a note of clarification, these are not 'new four-stroke rules'- at present there is nothing stopping any manufacturer from entering a 500cc four-stroke in the class as it is now. However as Honda proved with the NR500 many years ago it is simply not possible to extract competitive power from a four-stroke of similar capacity to the modern two-strokes. Although the traditional 500cc limit is steeped in history, it was clear that the new category had to be the absolute pinnacle, and hence a new formula had to be derived to allow the new bikes to be even faster then those we see racing today.

Music to the ears...

The new rules represent music to the ears of racefans who fondly remember the magnificent multi cylinder bikes of the 50's, 60's and 70's. The technical diversity that flourished in the Grand Prix classes throughout this period was nothing short of breathtaking, a number of multi-cylinder bikes running at or above 20,000rpm before limits were placed on the number of cylinders and the two-strokes moved in.

These new rules mean we will once again hear the wail of handcrafted prototype engines of varying configurations doing battle on tracks around the world.