BSA CRANK CONVERSION

Though many high-performance automotive engines are equipped with plain main bearing crankshafts, some are of the opinion that this type of crank is the Achilles heel of the BSA unit twin motorcycle engine.

The BSA racing department experimented successfully with roller main bearing cranks in the 60s and 70s, and for years companies in England have offered a service to convert the right hand crankshaft bushings on A7, A10, A50, and A65 to radial thrust needle bearings. This allows better control of end play, as well as end feed of the oil to the crank through an oilseal as on Nortons and most Triumph twin, allowing longer engine life. The big downside of sending heavy parts to England for North American customers, though, has been the huge cost of shipping back and forth, making this conversion quite un-economic, to say the least. As a result, very few engines have been modified this way by USA and Canadian BSA riders.

British Cycle Supply Company is now subcontracting this modification to an expert American machinist so we can offer this service at a realistic price and turnaround time. 

The conversion is available two ways for the unit twins:

a) Hidden conversion: This does not change the appearance of the engine at all, and feeds the crank via hidden oilways under the timing cover.

b) Outside conversion: This has a flexible oilfeed hose going from the front of the engine around to the timing cover to feed the end of the crank, a more economical way of achieving the same thing as the hidden conversion, and mechanically exactly the same.

The preunit twins are only available as a hidden conversion.

We require the customers clean bare crankshaft, RH crankcase, and inner and outer timing covers.

Canadian customers can ship the required components to our Canadian warehouse, and we will save you cross border shipping charges by transporting back and forth from the USA in our company Diesel truck
for free. 

US customers should ship directly to our US warehouse at 146 Porter Street, Hackensack, New Jersey, 07601.

Parts should be carefully packed in a very sturdy box or crate to avoid damage, fully insured. We will return to you in the same box when the work is complete, and can supply any other requested items such as gasket, seals, pistons, etc. at that time to allow completion of engine assembly.

PLEASE ALLOW AT 90 DAYS FOR PROCESSING AND SHIPPING. WE CAN SHIP BY FASTER METHODS IF TIME IS OF THE ESSENCE, AT EXTRA COST.