Ugly KTONK Noise

While mowing, my JD 425, 94 edition emitted an ugly KTONK and stopped. Tried to start it but the engine was frozen. Manually rotated the drive shaft and I was able to crank it but no engine start. The flywheel engaged okay but there was zero compression.
So okay guys, give me the bad news but please be gentle.

P.S. As an additional note, when I checked compression I noticed the inner electrode of one spark plug was loose and was touching the plug point. Obviously there was no spark out of the plug. I do not know if the engine running on one cylinder could have caused the mishap.

NCMau said:

While mowing, my JD 425, 94 edition emitted an ugly KTONK and stopped. Tried to start it but the engine was frozen. Manually rotated the drive shaft and I was able to crank it but no engine start. The flywheel engaged okay but there was zero compression.
So okay guys, give me the bad news but please be gentle.

P.S. As an additional note, when I checked compression I noticed the inner electrode of one spark plug was loose and was touching the plug point. Obviously there was no spark out of the plug. I do not know if the engine running on one cylinder could have caused the mishap.

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Have you ever changed the oil on it? did you get it used from someone who didn't take care of it?
If so your piston arm may be shattered. Don't jump to conclusions because I'm not sure.

JD is best said:

Have you ever changed the oil on it? did you get it used from someone who didn't take care of it?
If so your piston arm may be shattered. Don't jump to conclusions because I'm not sure.

Click to expand...

I got the engine on the bench and opened the crankcase cover about 3/4? The cam gear is metal and it is all in one piece, however I could see remnants of connecting rod(s) at the bottom of the case. This is not good news. I was hoping the cam gear was plastic and to be shattered, unfortunately it is not. So it looks like it is a bigger job for my pay grade that I had anticipated.
Question, I got the crankcase cover out about 3/4? but I am having hard time to pull it out any further. I tried to use an oak wedge and tap it on both sides but it not moving. I am trying to be extra careful not to cause any unwanted damage. All bolts are definitely out.
I could use some suggestions.