Originally Posted by JerryH
Most motorcycle cranks are of the "pressed together" type, which must be welded to hold together. It also means the bearings are not replaceable. The entire crank assembly, including the crank, bearings, and rods must be replaced as a unit. So it is impossible to be sure the clearances are correct from the factory.
While I'm relatively sure that some are welded I know for a fact that many are not. One of the services that my business offers is the rebuilding of "pressed together" crank assemblies.
A properly fitted, assembled and aligned crankshaft assembly should hold it's alignment with no problem and without welding.
I'm amazed at some of the run out figures that I'm seeing on this thread, we won't send a crank out unless it is true to .0002 (2 tenths of a thousandth) per end for a total runout of less than a half thousanth. This is in a racing application.