Although the rules forbid changes to the original carbs and pipes, the brothers used some of their 2-stroke racing engine knowledge to improve the stock parts where allowed.

“The crankshaft was fitted with a connecting rod from a current Yamaha engine, and we used a piston from a 750 twin PWC [Personal Water Craft] motor,” says Harry. A KX motocross ignition system was fitted to reduce weight and improve the electrical system and an air scoop was fitted to the cylinder head to assist cooling at high speed.