When considering a gear drive cam chest assembly, the Harley pinion shaft runout becomes extremely important.
The manufacturer of a gear drive assembly will always specify a maximum allowance for Harley pinion shaft runout. This allowance should not exceed .003″. It is very important to heed the manufacturer’s instruction and warning.
If a gear drive assembly is installed on a Harley crankshaft that is out of spec, it will cause excessive stress and the motor will have an overwhelming whining sound that usually increases with RPM.
Measure the runout with a dial indicator that is mounted to the motor case. With the bike in high gear and spark plugs removed, roll the rear wheel so that the pinion shaft turns and run out can be measured. If runout is under .003″, it’s a go. If over .003″, it should be a no go. If measurement is over the maximum spec, moving forward will be a gamble.