Ok, I know that this isn’t a car, but it operates like one and this is the best place I know to get an answer. I have a Craftsman riding lawnmower with a 26HP Kohler Pro “Courage” engine. When I go to start it, I get a very nasty griding sound from the engine or a few seconds while it attempts to turn over then it dies to nothing. The battery is good, I changed the spark plug (unrealted possibly, but it needed to be changed), and I beleive the air filter is fine. So any ideas what I should be looking to fix? Thanks!
So the engine won’t run at all? You probably need to charge or replace the battery and the noise is from the starter not quite having enough oomph (technical term) to fully operate.
If the battery has a full charge, the grinding would only have a few sources. One is a problem with starter engagement. Its basically the same as on cars. There is a bendix gear that has to fly out and engage the flywheel to turn the engine and then retreat. When there is a problem with that it makes terrible noise. So take a look at the starter as you turn the key and see what it is doing.
One other question is whether you’ve popped the hood to look for debris in or around the engine shroud.
The last thing would be that something let loose inside of the engine. What did the old plug look like? Pull the spark plug again and peer down in there with a flashlight. Turn the engine by hand and listen. Have the valves ever been adjusted?
If this engine is an overhead valve type then the valves need to be properly adjusted. The reason is that the automatic compression release will not work if the valves are out of adjustment. The compression release make starting the engine much easier. Ditto to what Cig said as well.