JD425 Big Problem

[NCMau]

While mowing, my JD 425, 94 edition emitted an ugly noise 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.
Am I looking to an engine rebuilding job? I really hope not!!!!

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.

 

[bobmisi]

When you crank the engine, is the piston moving up and down? Sounds like something hit the spark plug, like the piston, if the connecting rod let go. Therefore you would have zero compression in that cylinder.

 

[NCMau]

When you crank the engine, is the piston moving up and down? Sounds like something hit the spark plug, like the piston, if the connecting rod let go. Therefore you would have zero compression in that cylinder.

I can not tell from the spark pug hole if the pistons are moving. My guess are not. Also when it was cranking the front PTO was also turning, then locked up again. The connecting rod sounds like a candidate, but also the timing gear since this early model had a plastic one. I am debating what my best approach would be, to remove the time cover and look at the gear, or take the engine out and go from there. If possible, I am just trying to minimize my work.

 

[NCMau]

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.

 

[Coyote machine]

Describe further what you mean by crankcase cover. Are you referring to the oil pan under the engine, or a different cover? Do you have or can you take pics and post them? How about a JD link to a parts breakdown schematic?

Here's a link to a for sale rebuildable 425 engine with the cover I believe you're referring to, removed. John Deere 425 445 Kawasaki FD620 Engine Block for Rebuilding Free Shipping | eBay If you look closely you'll see round dowel holes that line up and help mate the cover to the block. Those could be what is hanging up the cover removal. I'd do a google search for JD 425 engine problems/fixes/rebuilds etc. before going much further. There are many possibilities to choose from.:2cents: