And if you don't happen to own an impact wrench - here's a trick that works very well.
Actually I'm cutting and pasting this from a post I did regarding a John Deere STX38, so some of the details may be different - but you can figure that out:
Remove your spark plug. Take a piece of clothesline and feed it into the cylinder through the sparkplug hole. Once you get enough in there, try removing the clutch bolt again. The rope will block the piston and keep it from making a full cycle, allowing you to remove the bolt.
The bolt is usually very tight so put some effort into it. It's so tight that sometimes people fear that it may be reverse threaded and they're going the wrong way. IT IS NOT REVERSE THREADED!!!! It's just a normal bolt.
The clothes line is soft and won't hurt anything.
Obviously use a good length of rope and leave a good length hanging out so you can pull it out easily when you're done.
A long thin pair of needle nose pliers helps a lot in feeding the line in since the spark plug hole is pretty deep in the head.
And you may find that if it's not going in easily that you have to turn the engine a bit to get the piston low in the cylinder to give you more room.
So it may take a few attempts, but it works well.
And once you get your bolt out - keep an eye on the clutch and parts as you remove it. It's not a one piece unit. The clutch itself can come apart, and there's a two inch (or so) collar that fits on the shaft. It's not complicated, but still, you'll feel better about putting everything back together if you've seen how it all came apart.
Good luck!
