Crank rebuild


Step by step rebuild and rephase of a crank by Daryl Hutcheon

Daryl Hutcheon's Professional Motorcycle Tuning is doing crankshaft rebuilds and rephases almost daily so who better to explain the procedure than the man himself.

The whole process begins by completely disassembling the crankshaft and cleaning everything. The crank pictured above will be a 270 rephase which explains the splined shaft and additional internally splined crank flywheel. As you can see the flywheel on the right has been modified by machining the bearing mount down to the width of the bearing plus 1mm. The flywheel on the left is unmodified and still has the cut-out for the cam chain sprocket to key into.

All new bearings and connecting rods are used in the assembly as required.

All the component parts are then pressed together with the correct clearances on the big end of the conrod.

Once the assembly is completed it is adjusted for correct alignment.

It is then welded and is then ready to install in the motor. This procedure is followed for all crank rebuilds except welding is not always required on a stock rebuild, it is however highly recommended for all rephased crankshafts.