PICS of Kubota Engine and (hopefully) rebuild

[Delmar]

PICS of Kubota Engine Tear Down and (hopefully) Rebuild

I recently bought a G1900 that wouldn't start, PO said he thought it was the injection pump. 950 hours and overall in pretty good shape. I have another G1900 and bought this really cheap for parts. However, I'd really like to get it going if I can.

I started this thread and, with the help of others, went through all the troubleshooting I could. http://www.orangetractortalks.com/forums/showthread.php?t=25573

Finally decided to start tearing it down and see what's going on in there. Only problem is, I know very little about what I'm looking for! Any guidance or advice is appreciated.

Here's the start

I followed instructions in the engine WSM. Pretty straightforward. Kept some groups of parts in baggies. Arranged others so I would remember how they came out.

When I removed the head, quite a bit of coolant spilled out, even though I had drained the radiator. I assume I should have drained the block but I missed it. I soaked up the coolant that spilled into cylinders. Here's the block after head removal.

Here's a closer look at the cylinders. They are a little "rusty" looking, and there is some very shallow pitting, but no scratches or anything that will catch on a fingernail. Should the cylinder walls be shiny and "new" looking?

 

[Delmar]

Re: PICS of Kubota tear down Engine and (hopefully) rebuild

The head gasket looked like it was in good shape. I didn't see any areas that looked bad.





Again, I'm a novice so I'm not sure exactly what I'm looking for. Anything look troublesome in these pics?

The engine turns freely, although I'm not sure how freely it should spin. I'm applying maybe 15lbs of pressure to spin the flywheel.

Does anyone know if I can remove the pistons through the oil pan opening? Or, do I have to remove the block?

Thanks for any input!

 

[Delmar]

By the way, what looks like metal shavings in the closeups is actually little drops of coolant. I didn't see any kind of metal.

 

[Ike]

You should check the bores with a bore guage before rebuilding it. Look at the very top of the cylinder where the piston does not go and take your thumb nail and slide it up the cylinder wall. See if there is a lip at the top, If there is it means the cylinder has wear in it' If there is a big lip you cylinders may be out of round.

 

[JohnnyFbomb]

I would have figured out why it didn't run in the first place before pulling it apart.

That said, those bores look great and they should with only 950 hours on it. I can see there's no ridge. Get a pin punch, number the pistons so you know what hole they came out of. I would hone the hole by hand, re-ring and put them back in. From the pictures, I can't see anything wrong with the gasket. If it is the injection pump, you'll have to send it off to an injection shop and flow test it. If it was mine, I would have it maxed and balanced. I would also have the injectors flow and pop tested.

 

[Delmar]

Thanks, Ike and JohnnyFbomb. I went out checked the top of the cylinders for ridges at top (and all the way down for that matter). Nothing. Smooth as glass. I don't have a bore gauge but can take it to a machine shop if needed.

I started tearing it down because of low compression. I replaced the injection pump and starter with known good ones (I have another tractor of the same kind) and it still wouldn't fire. Even tried ether (I know, I know...), still nothing.

I guess my next step is removing the pistons. Still not sure whether I can do that through the oil pan hole or if I have to remove the block.

Thanks for your helpful posts.

 

[North Idaho Wolfman]

The reason for the low compression is the pitted cylinder walls and most likely damaged rings.

You pull the pistons out the top, but to get the cylinders bored and or relined you will need to completely tear it down.

 

[JohnnyFbomb]

The reason for the low compression is the pitted cylinder walls and most likely damaged rings.

You pull the pistons out the top, but to get the cylinders bored and or relined you will need to completely tear it down.

I had to save the pic and zoom in to see what you were talking about.

 

[North Idaho Wolfman]

I had to save the pic and zoom in to see what you were talking about.

Do you see it now?

It really doesn't take a lot to make them leak down when your trying to get it up to 400 some pounds.

 

[ironpony]

I agree with wolfman, smooth shiny cylinders are worn down along with the pitting, they should have a nice crosshatch visible. The cross hatch from honing actually allows oil to be held in the "scratches" which lubricate the cylinder. The cross hatch also seals the rings to the cylinder walls. Pull the pistons out the top, check specs on cylinders and if you are lucky you might be able to hone them and install new rings. Those pits do look pretty deep though, might just pay to put in liners and new pist0ns.

 

[ironpony]

Also the head does not look bad at all, the different colors in the cylinders tell a tale of the fuel burning, notice they are different. The darker ones were not burning efficiently.

 

[JohnnyFbomb]

Do you see it now?

It really doesn't take a lot to make them leak down when your trying to get it up to 400 some pounds.

I really need to update the size of my screen

 

[CountryBumkin]

I started tearing it down because of low compression. Thanks for your helpful posts.

Just curious. How do you know you have low compression? Do you have a compression gauge - or are you just determining that based off the symptoms?

 

[North Idaho Wolfman]

Just curious. How do you know you have low compression? Do you have a compression gauge - or are you just determining that based off the symptoms?

He had tested it in his other thread!
http://www.orangetractortalks.com/forums/showpost.php?p=191702&postcount=12

 

[North Idaho Wolfman]

I really need to update the size of my screen

Yes Dual 44" monitors do come in handy!

 

[Delmar]

Got the engine block out last night and took the block and head to a machine shop this morning.

The pitting in the cylinders appears worse in the pictures, I think. I could barely feel the pitting when running my fingers over those areas. However, I don't have any real frame of reference. I didn't see any obvious wear on the pistons and rings. I left them at the machine shop, too, and they said they would evaluate them, along with the valves and seats.

Hopefully the cylinders will only need honed.

Hardest part of the project--so far!--was getting the engine mounts out of the way so I could slide the engine forward. Any tips on sliding engine back in place?

Also, if the cylinders do get bored, do I have to get new pistons or just oversized rings?

Thanks for the help!

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[North Idaho Wolfman]

If it need bored then you go .5mm over and use this:
http://www.kumarbrosusa.com/kubota/overhaul-kit-d722-.5mm.html

If it just needs honed, use this:
http://www.kumarbrosusa.com/kubota/overhaul-kit-d722-std.html

These kits have all the parts needed, I recommend replacing the pistons because on these small engines ring wear almost always means ring gap wear too.

 

[botaskinner]

Not a professional diesel mechanic here, but I'd recommend taking the block to the machine shop if you haven't already and have them look over that center cylinder.

I wouldn't be surprised if there was coolant getting into the center cylinder, those pits in the cylinder wall tell a story. Also, the center combustion chamber looks cleaner that the outside ones, could be a sign that water was getting into the cylinder and the resulting steam cleaned off the head surface. It's normal to see a bit of soot from normal combustion as in the outside cylinders.

Are you certain if that head gasket that came off the engine was original? Could be a repair attempt was made once before without really fixing the problem.

 

[Delmar]

Thanks for the rebuild kit links, NIW.

The machine shop said it would likely be next week sometime before I get the block and head back.

I'm not sure the head gasket is original. It does look to be in pretty good shape but, then again, the engine only has 950 hours on it.

I did have a funny moment when I removed the oil pan. Saw a long piece of metal and thought it was a broken engine piece - it was the oil dipstick! Forgot to remove it before I turned the block upside down to remove the pan.

I think I will try to run the engine when I get it reassembled before putting it back in the tractor. If there's a problem it's a lot easier to tear back down outside the tractor. Any reason not to do this?

I'll post agsin when I get the engine back.

 

[Russell King]

Re: PICS of Kubota Engine Tear Down and (hopefully) Rebuild

You can have dye penetrant test/magnaflux test done on head and block to see if they are cracked before they machine them. Machine shop should be able to do that if you ask.


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