Kubota engine rebuild problem

   / Kubota engine rebuild problem #1  

jimd333

New member
Joined
Sep 9, 2013
Messages
9
Location
Newtown, ct
Tractor
cub cadet 1641
The engine is a two cylinder diesel (Z500).
It's forty years old and has been rebuilt before.
I recently changed the piston rings. On startup, the engine lit off and immediately seized. I was told by Kubota that the connecting rod cap bolts are YTT ( yield to torque) bolts and shouldn't be reused as these were used at least two times before.
I removed the end caps and found no metal or damage, and while the crankshaft now turns, I believe the number 1 piston is hitting the cylinder head.
I was hoping not to have to remove the cylinder head again. Has anyone experienced a "spun bearing " before?
 
   / Kubota engine rebuild problem #2  
Removed end caps or rod caps? If it was rod caps, you'd see the bearing problem right then. Are the Pistons turned the right way? Are the rod caps? I mark everything before I take it down. Are the rod caps on the rod they came off of?
 
   / Kubota engine rebuild problem
  • Thread Starter
#3  
Yes, rod caps is what I meant. It's too late to mark now, but I was working with a flashlight last evening. The number stamps on rod caps looked to be properly oriented with the rod.
What should I look for next? Should the bearing be replaced? Can I get this done without removing the cylinder head? Thank you.
 
   / Kubota engine rebuild problem #4  
I removed the end caps and found no metal or damage, and while the crankshaft now turns, I believe the number 1 piston is hitting the cylinder head.
Is the piston hitting the head or a valve? Is there an foreign object smashed between the head and piston?
 
   / Kubota engine rebuild problem #5  
Is the piston hitting the head or a valve? Is there an foreign object smashed between the head and piston?
Yep, they don't stop on their own.

I have the same engine in my Kenbota. It started life as a G3200 lawnmower with 1300+ hours. It's still running strong. The only thing I did was clean it, paint it and changed to a "real" alternator. It's no longer a lawnmower. ;)

Kenbota FEL10.jpg
 
   / Kubota engine rebuild problem
  • Thread Starter
#6  
Is the piston hitting the head or a valve? Is there an foreign object smashed between the head and piston

Yes, the valve is being struck. I have very limited time to work on this, but will check in soon. Of course, everything is out of sequence! Thanks.
 
   / Kubota engine rebuild problem #7  
Timing marks lined up? New valve springs? Pushrods/rockers in same places? Pistons in the same orientation? Lash set? What changed other than the rings?
 
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