I have a Sears DLT mower with the 25 HP Intek in it. Have an issue with it spitting and sputtering with the PTO engaged. Black smoke just rolls. Turn the PTO off, and it will smooth back out again. I have checked everything I can according to the manual. It has new plugs and the valves have been adjusted. New oil change, air filter. I pulled the flywheel this morning to check the key there and all is good. Ran a diode test and they check okay. Cleaned the inside of the flywheel and it charges better now. Also, if you let it set overnight, takes a squirt of carb cleaner to get it to fire. I have an electric fuel pump on it and that didn't help with any of the issues. I'm thinking the coil pacs are getting weak, missing under load. Any other ideas?
Here's the plugs. Only an hour or so run time on them.
This was inside the flywheel.