BSA A10 Torque Specs

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BSA A10 Torque Specs
BSA was originally a British military arms factory. (British flag image by Tom Davison from

The BSA A10, otherwise known as the Golden Flash because of its gold livery, was a British motorcycle made by the Birmingham Small Arms Company (BSA). It was built from 1949 to 1962. Torque, in terms of engine maintenance, refers to the amount of force needed to tighten a component. Specifications are usually given in foot-pounds.

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Cylinder Head Bolts

According to BSA Service Sheet No. 208, when you are replacing the cylinder head bolts, you should "make them all really tight." Work diagonally to ensure even tightness, leaving the central inclined bolt until the end. When all the bolts are "right down" you should give them a "final wrench" to ensure that they are really tight.

SRM Classic Bikes is more specific in its recommendations. According to SRM, the torque settings for all cylinder head bolts on the BSA A7 and A10 models from 1950 onwards is 32 foot-pounds.

Crankshaft Bolts

BSA Service Sheet No. 208 gives advice on crankshaft replacement. The crankshaft, also known as the crank, is the part of the engine that changes the movement of the piston(s) into rotational motion. If you have replaced the crankshaft on your A10, you may be able to refit the original flywheel, if it is serviceable. To do so, pass it over the drive side of the crankshaft and bolt it to the flange with six high-tensile bolts. The service sheet advises only that you securely tighten the bolts and gives no specific torque settings. The sheet does specify that the bolts should be "peined over on to the nuts to lock them." In other words, struck with the ball-peen of a ball-peen hammer, or ball-peen hammer, until the bolt heads deform enough to lock. Thanks to the advance of bolt technology, this old technique for fixing bolts is now considered primitive. However, if you wish to rebuild an A10 to authentic original standards, you may want to reach for your hammer rather than your torque spanner.

Big End Bolts

A torque spanner should be used for tightening these bolts to make sure that they are not overtightened. Two types of big end bolts were used. On early models, the bolts were 22 T.P.I. B.S.F. These have 22 threads per inch (TPI) using the British standard fine (BSF) standard. For these, the torque spanner should be set at 10 foot-pounds. On later models, the bolts used were 26 T.P.I. C.E.I. These have 26 threads per inch using the Cycle Engineers' Institute (CEI) standard. For these, the torque spanner should be set at 8-1/2 foot-pounds. The latter type bolts, complete with nuts, can be used as replacements for the earlier type. From 1956 onwards, the torque setting is 22 foot-pounds.

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