Have a JD 322 with a 3 cylinder Yanmar gas engine,that I use in the cemeteries I take care of. Problem is that after about 30 minutes, it quits running. It will start again after a few minutes, but quits again in a shorter period of time. Put 3 new coils in and changed the module/regulator. Any ideas. Am I missing something simple? When it runs, it runs great.