Long Stroke Crank – 2000 Nord & Twin Spark

Designing from scratch using modern knowledge of optimum crank design and CAD to optimise the crank for 2000 Nord and Twin Spark engines.

The stroke of the crank is stretched to the maximum whilst ensuring it fits the block without modifications, increasing it by 5.5mm to 94mm, which gives just over 2100cc with 84.6mm bore, or just under 2300cc with 87mm bore.

Our development engine has produced 15BHP extra versus an original. Resulting in Twin Spark engines producing 230-240BHP and Nord engines producing 220-230BHP.

Conscious to remove any weight where necessary, with the big ends specially bored hollow to reduce centrifugal weight. The counterweighting has been optimised with very specifically shaped and sized webs to ensure perfect piston & rod counterweighting at high revs. The result is a long stroke, increased capacity crankshaft that revs up faster and is more free revving than a factory crankshaft.

After the billets are turned they undergo a stabilising process where they are reheated and left to cool, this removes any of the machine stresses and further improves the qualities of the material, once the cranks are finished milling they undergo an internal rumbling process that deburs the machined surfaces and also assists with further destressing of the material.

Crankshafts are pre and post-nitride CNC ground for accuracy and control of journal sizes as well as nitriding case depth uniformity. Gas nitride hardening achieves a bearing surface hardness up to 900 Hv to approx. 0.5mm.