Kubota d722 spun rod bearings

I have a Kubota d722 that came out of a ex-military clubcar 4x4 UTV . apparently in the 306 hours of its life the oil was never changed & it must have run low on oil. When I took the head off, I noticed that the cylinders still have cross hatching BUT their is dark circular spots on either side of all 3 cylinders. Its right where the ends of the piston wrist pin would be. There is no scoring, just a dark patch. Would that be from the bad rod bearings letting the rod wiggle?

Does anyone have experience in rebuilding small Kubota engines? I'm trying to find my break point. I've only worked on Cummins engines, not sure how much it cost to have these small engines honed and turning the crank. With a rebuild kit being $580 and machine shop labor, i m wondering if it would be cheaper to just buy a engine off eBay? I find these d722 kubotas for around $1200-1500 online.

1200-1500 for another used one with unknown history. I'd strip it down and take it to a machine shop to get it checked out, then get an estimate.

That being said, if it failed because of lack of oil/old dirty oil, the rest of the engine probably isn't in much better shape. That's when it gets spendy.

We learned on the 3 cylinder kubota engines in college in my drivetrain class. Very easy engines to work on. Can be torn down in an hour. As mentioned I would revuild given you will probably have less in it than a used one and you will know what you have.

Agree with above. If u dont feel comfortable the machine shop could assemble what i dont want to. Just an option. Added cost.

Thanks for the info guys. I guess i'm going to tear the one I have down. It is neat that you can have the cylinder head off in 5 minutes and the block torn down pretty quick. Now I just need to find a reference guide for how to get everything re-aligned like the cam gear, injection pump etc. for re-assembly.

If I remember correctly the Kubotas that I have worked on had good timing marks on the gears. One gear would have just one dot and another would have two dots and the other would have three. That was on the 4 cylinder engines found in bobcat skid steers. I would assume that the little three cylinders are the same.

Ok, I've got to go back to the drawing board on this one. I think my assumption that it had spun rod bearings might have been incorrect :doh:.

When I took the oil pan off I had seen that that area on the crank that surrounds the rod caps had bluing, which I was assuming was from heat? Didn't think this was normal so I assumed it was from possible spun rod bearings.

Second reason why I thought it had spun rod bearings was from the moment I dropped the pan. I had seen one piece of metal in the pan. It was magnetic (pictures attached). The piece of metal was somewhat smooth on one side and VERY rough on the other side which kind of perplexed me. It's almost like gritty/rust on one side. Don't know if it is bearing material.

A bit of information that I left out that I believe is important: When I bought this utility vehicle I had never heard the engine run. All I knew was that the engine would rotate 3/4 in either direction but would NOT do a full rotation. I had previously bought a kubota D1105T from a local mower shop so I could tinker with it. The D1105T that I bought from the mower shop had the same symptoms and upon tearing it down it had a broken rod bolt and the rod cap was 1/4 of the way off.

Fast forward to the motor im working on from this UTV. When I took the head off I noticed #1 piston was caked up with a 1/4" layer of what looked like seed. I guess when sitting a mouse had climbed through the intake and nested? That was apparently what was stopping the engine from full rotation. Kind of I guess hydro locking it. BUT this does not explain the metal I found in the pan.

I took all 3 rod caps off today and all 3 rod bearings and crank surface looked like new! So do I tear into it further to find where the metal came from? I cut into the oil filter and there was no metal to be found in the fins of the oil filter.

The picture of the head only shows some of the seed....I had already out of frustration cleaned the top of the piston and most of the head.

Almost looks like a thrust washer to me. Are the thrust washers still in it or can you tell?

I can see the lower thrust washer that's about it.