Ask Me Help Desk - Craftsman 20HP mower won't start

The culprit is a 7 yr old Craftsman lawn tractor, model number 917.273060, 20 HP OHV Kohler engine.
Until now, this tractor has always started easily and without any hesitation. The other day I tried starting it and all I heard was a slight cranking sound and then a steady noise, kind of a hum. I figured the battery, the solenoid, and the starter were the first things to check.
To be honest, I didn't really know how to test them, so I looked on the internet and tried a few suggestions. I hooked the battery up to the starter with jumper cables, no change. Then I connected the starter to my truck battery, same thing. So I deduced the battery is fine and the starter is bad. I ordered a new one, put it on and nope that wasn't the problem.
As I said, I'm a novice, but after looking closer it appears the starter moves up and engages the flywheel, the flywheel turns slightly as if it might start and then everything stops, except for that kind of electric motor hum sound (don't know how else to describe it). I can manually turn the flywheel.
I tried cranking it without the spark plugs, but it makes no difference. Could the valves need adjusting or is there something else I could try before I haul it to the repair shop?
Thanks for any suggestions.

So even with the spark plugs removed you still can not get it to turn over? But you can turn it by hand?

Quote:

Originally Posted by sprouts

The culprit is a 7 yr old Craftsman lawn tractor, model number 917.273060, 20 HP OHV Kohler engine.
Until now, this tractor has always started easily and without any hesitation. The other day I tried starting it and all I heard was a slight cranking sound and then a steady noise, kind of a hum. I figured the battery, the solenoid, and the starter were the first things to check.
To be honest, I didn't really know how to test them, so I looked on the internet and tried a few suggestions. I hooked the battery up to the starter with jumper cables, no change. Then I connected the starter to my truck battery, same thing. So I deduced the battery is fine and the starter is bad. I ordered a new one, put it on and nope that wasn't the problem.
As I said, I'm a novice, but after looking closer it appears the starter moves up and engages the flywheel, the flywheel turns slightly as if it might start and then everything stops, except for that kind of electric motor hum sound (don't know how else to describe it). I can manually turn the flywheel.
I tried cranking it without the spark plugs, but it makes no difference. Could the valves need adjusting or is there something else I could try before I haul it to the repair shop?
Thanks for any suggestions.

Hmmmm,

This is a long shot but just for grins, remove the spark plugs, turn on the ignition and see if you can still turn the flywheel. If not, the electric clutch has engaged. Even a good starter may not have the guts to turn the engine and the mower deck at the same time.

Just a thought.

I have tried everything I have read and everything anyone has suggested and nothing has made any difference. I've been told this tractor has hydraulic lifters so valve adjustment wouldn't be an issue anyway. I've learned a lot, but it's all over my head now. Time for a repair shop to take a look at it. The upside to this is that I'm getting in shape with all the push mowing. Thanks for the help.

I dropped it off at a repair shop this morning and the mechanic didn't have time to look at it, but he did turn the key once and said "sounds like the starter is bad". I told him the starter tested good, so he's going to take a look at it in the next few days.
As I said, when I try to start the engine it rotates slightly and then abruptly stops. It doesn't matter if I'm turning the key or jumping the starter with my truck battery. It also doesn't matter if the spark plugs are in or out. It always does the same thing. I can manually turn the flywheel a complete revolution. Sometimes it's kind of difficult to turn, but I can always turn it. Someone suggested the flywheel key. I don't know anything about this.
I'll keep you posted on the outcome, in case someone else has a similar problem. Thanks everyone.

Quote:

Originally Posted by sprouts

I dropped it off at a repair shop this morning and the mechanic didn't have time to look at it, but he did turn the key once and said "sounds like the starter is bad". I told him the starter tested good, so he's going to take a look at it in the next few days.
As I said, when I try to start the engine it rotates slightly and then abruptly stops. It doesn't matter if I'm turning the key or jumping the starter with my truck battery. It also doesn't matter if the spark plugs are in or out. It always does the exact same thing. I can manually turn the flywheel a complete revolution. Sometimes it's kind of difficult to turn, but I can always turn it. Someone suggested the flywheel key. I don't know anything about this.
I'll keep you posted on the outcome, in case someone else has a similar problem. Thanks everyone.

Do post the final problem when it's found. This one is definitely worth knowing.

I have the same mower and on the top of the starter there is a plastic gear that goes bad. I have went through three of them.
You have to take off the top engine cover and a cover on the side to see this part.