With a bore and stroke of 72 x 61.2 mm, the power unit displaces 249 cm3. The engine is mounted low in the frame, contributing to a low centre of gravity. Flat-top piston and pentroof combustion chamber deliver a 11.0:1 compression ratio. Lightweight piston, piston pin and connecting rod allow power-producing revs. 4-valve DOHC cylinder head provides maximum valve area for optimum flow. Low reciprocating weight (thanks to the use of a cam lobe for each valve, with shim-under tappet arrangement) contributes to higher efficiency at high rpm. Where 6th gear on the previous model was almost an overdrive gear, revised gear ratios see the 6th gear set closer to the 5th gear, facilitating shifting for increased performance off-road and on.