The only fix on the swing arm version if the swing arm goes bad is a camshaft replacement. I have been replacing quite a few of the 310000 series cams because of the ACR failure (bad design in my opinion). Usually the ACR completely comes apart and the electric starter can no start the engines even the valves properly adjusted. I have one case where the ACR fragments actually took out the oil slinger/governor gear.
I have seen several of the smaller cams where the hair spring fails again the only option is a camshaft replacement. Probably wondering why I called it a hair spring, it is because looks a strand of hair and easily missed.
The main to make sure on all designs is the valve clearance is first setup correctly as most it is it and not the camshaft ACR. Only after this is done and you still don't get ACR bump then you look at the camshaft. This ACR bump can either on the intake or exhaust just depends the engine design.
BTW I subscribed to the checking of the least invasive things first or what is called the KISS system. KISS = Keep It Simple Stupid. No reflection on the experienced tech but beginners can over complicate things.
