From an official FIM press release:

In a meeting held today in Silverstone, the Superbike Commission, composed of Messrs. Claude Danis (FIM), Paolo Alberto Flammini (SBK International), Takanao Tsubouchi (MSMA) and Giulio Bardi (Team representative), has
unanimously approved the following proposal:

-To allow 1000cc 4-cylinder motorcycles to take part in the 2003 Superbike World Championship. The 1000cc 4-cylinder motorcycles will compete under the current Superbike World Championship Technical Rules and Specifications except from:

a) The engines will have an air restrictor specified as follows:

-26.3 millimetres by 1

-18.7 millimetres by 2

b) Minimum weight: 168 kg

The above rule will therefore be included in the 2003 Superbike World Championship rulebook. For the sake of clarity, the current FIM Superbike World Championship rules will remain unchanged in 2003, save for the above provision.

FIM Road Racing Commission President Claude Danis will present this modification to the rules to the Managing Council in its session of June 22-23.