Classic British twin Stroker Crankshafts!

Ed G Cranks has been building building stroker, and other custom stroke crankshafts, for over 5 years. These cranks are for BSA and Triumph pre-unit and unit engines and for some Norton engines. These cranks fit most 650cc or 750cc BSA and Triumph unit construction engines and Norton Atlas or Commando engines. Stoker cranks can be built for pre-unit BSA and Triumph engines but this requires modification of the crankcases. Most big twin stroker cranks are made from modified Norton crankshaft components and can be used for stock or racing engines. Each crankshaft uses a new, smaller flywheel that allows clearance for any camshaft. As with all crankshafts we build they are machined, welded, ground, balanced and nitride heat-treated to fit your engine without modification.

We are the only crankshaft vendor that supplies a stroked, heat-treated and balanced offset crankshaft with appropriate camshafts. Custom length connecting rods can be purchased from various suppliers dependent on engine brand, type and stroke. Contact us for information about various vendors as we don't sell connecting rods. All components are ready to install using your stock or modified crankcases, pistons, timing gears, drive pulleys and barrels.

If you are a BSA or Triumph unit engine owner you can combine a stroker crank with various after-market barrels. SRM sells large BSA A65 barrels and custom machines them to suit the stroke of your engine and the length or your connecting rods. When combined with a stroker crank this means you may be able to build a smooth engine at over 900cc displacement. Actual displacement will depend on piston size and stroke specified. Triumph T140 engines can be built with displacements greater then 850cc using stock barrels (depending on piston size). As with other crankshafts that Ed G Cranks builds you must supply the weight of one piston with rings, wrist pin and cir-clips for balancing.

It is possible to change the stroke on a Norton crankshaft by up to 4mm to make a 93mm crankshaft adding a small, but noticeable, increase in displacement. Stock Norton stroke is 89mm. Custom length connecting rods or a stoker plate 2mm thick is required. This adds $250 to the price of a standard Norton 89mm stroke crankshaft.

Triumph 89mm Stokers

Triumph 92mm Stroke

Triumph 500 69mm Stroker




Cost Savings: A typical Triumph stroker crank is made using splines for the drive side and mount for an alternator. BSA and Triumph Stroker cranks include splines on the drive side and new threads and key way on the timing side. $300 USD can be removed from the crankshaft price if tapered Norton drive sprocket mount is retained on the drive side such as when using a belt drive sprocket. Contact belt drive suppliers, such as Tony Hayward, as they can sell you a Norton-type sprocket with the same number of teeth as their Triumph or BSA belt drive kits. Alignment between drive pulley and clutch must be checked if using a Norton chain drive sprocket on a BSA or Triumph stroker crank as a spacer may be required to position the clutch to align with the Norton drive sprocket.

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Stroker Displacement information

Stroker Piston and Connecting Rod Specification

Camshaft Information

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