This should take some the guess work out.
NOTE: the 74380 (Timer Cutter 4200) has 10 different serial number breaks so the serial is needed for the correct mower parts. The one I check had the Kohler SV590-0023 engine (The bucket engine design).
Per SM Valve clearances on the SV590 are .005 IN and .007 EX. Once the clearance set hold nut in position and torque set screw (T15 Torx drive) to 5.5 N·m (50 in. lb.), double check clearance clearance once set screw is torque; may need need resetting.
Also I have seen the starters to be a problem on these engines as the bushings wear out causing binding. So if it is not an ACR issue it can be the starter itself.
Also resealing the valve cover it is prefer you use either Permatex Ultra Black or Ultra Grey RTV. Surfaces must be oil free. Use Permatex surface prep / accelerator for best result along with it being allowed cure for at least 12 hrs before starting the engine. Finger tight the screws and let cure then torque them to 65 in-lbs. The reason behind this procedure is that the RTV will cure slowly in a sealed environment plus if oil is allow to contact the RTV it will not cure properly.

