FD620D 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. While it was turning, the front PTO was also turning. Then the engine locked up again.
I guess I am looking to perform some kind of surgery. My first wild guess would be the timing gear, which for this early model is plastic. What would be a reasonable approach, take the timing cover off or take the whole engine off and go from there?

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.

 

[reynoldston]

Do a leak down test. That will tell you what direction to go.

 

[Rivets]

My money is on a broken connecting rod, piston was going up when the rod broke and piston hit the spark plug. Pull the engine and take a look inside.

 

[NCMau]

My money is on a broken connecting rod, piston was going up when the rod broke and piston hit the spark plug. Pull the engine and take a look inside.

You are right. I got the engine on the bench and opened the crankcase cover about 3/4 in. 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 damaged, 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 in. 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.

 

[VT JD]

NCMau,

There may be some corrosion on the end of the crankshaft that sticks out beyond the cover. You can polish it off with steel wool and then lube it up before trying to remove the cover.

 

[NCMau]

NCMau,

There may be some corrosion on the end of the crankshaft that sticks out beyond the cover. You can polish it off with steel wool and then lube it up before trying to remove the cover.

Will do. Thanks.

 

[NCMau]

NCMau,

There may be some corrosion on the end of the crankshaft that sticks out beyoncan polish it off with steel wool and then lube it up before trying to remove the cover.

Well, I pushed the cover all the way in, removed the seal and I sanded the exposed bearing part of the shaft considerably. Still I have problem pushing it more than 3/4-1 in. The shaft looks slick and not deformed. I am just wondering if a wheel puller two or three jaws would be a way to remove it. Actually I don't think this would be a good idea since the cover is cast aluminum, but I am open for suggestions.