BSA 500 650 Timing Side Main Bearing Bush (1) -.020 PN# 68-0657-020

Description

BSA A50 A65 Crankshaft Bushing Standard '66-72 US PN# 68-0648 -020 68-0657
This crankshaft bush is specified for 1966 and later BSA twins, which is dimensionally correct for the engines produced after the introduction of the drive-side roller bearing. The crank bush is a critical component in the lubrication system, as it not only supports the timing-side crankshaft journal, but feeds oil through drillings in the crankshaft past the sludge trap to the big-end bearings. If the bushing becomes excessively worn, a loss of oil pressure will result and engine damage may occur. This bush is manufactured to an undersize of .020″.
Made in small batches under strict quality control by European Spares Limited in the US, the BSA A50 and A65 timing side crankshaft bushings are made from a proprietary bronze and machined to exacting specifications. The OD is 1.813″, ID is 1.479″, and the overall length is 1.010″. The lip is .090″ thick.
The crank bushing is an interference fit in the right crankcase and requires a precise tolerance between the bore of the bush and the timing-side main journal of the crankshaft. Oil is pressure fed from the oil pump through a groove machined into the exterior of the bush. There are four drillings that align with the oilway on the crankshaft journal, directing the pressure-fed oil through the crankshaft.
The fitment of the BSA twins crankshaft bush is normally reserved for experienced mechanics and generally the crankshaft bush will require line boring by a machinist to guarantee concentricity of fit with the crankshaft journal. It recommended to review the installation procedure in the workshop manual before attempting to fit this bushing into the crankcase.
Please note: Due the nature of the product, we unfortunately do not accept returns on bearings, service tools or electrical components. Please be confident about your purchase before ordering. If you have questions, please contact us.
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