FIXED Broken Kubota D722 engine

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Tazza

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A few months back i aquired a D722 engine that had a broken crank. I was told it hadn't done much work (which it hadn't, the bores still had cross hatching marks). I was speaking to a buddy last week and he said he had one that had a knock, used oil and smoked that i could have. I promptly picked it up and on the weekend pulled them both down to try and make one out of 2. For a secondhand crank they wanted $800 for!
It seems the one with the broken crank was run out of oil, all the centre main bearings had been spun BADLY and i can only assume the slop allowed the crank to flex and snap.
Long story short, i swapped cranks and big end bearings and it now works a treat! it will even start on compression alone. This on an in-direct injection engine is pretty good. Total cost of $0, i even managed to use the old head gasket sprayed with Hylomar (if thats how you spell it).
I found out what caused the smoke and knock in the engine with the good crank, the nozzle tip in the injector on number 3 was stuck inwards making the fuel drip and not spray. It has eroded a crater into the top of the piston, i had only heard that leaky injectors will melt the top of pistons. I can now confirm this! ensure your injectors are in good shape or you WILL do damage to your pistons.
I will post pictures when time allows, if anyone wants to see it that is.
 

Tazza

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I would like to see the pictures whenever you feel like posting them :)
I'll try and post them tonight.
I really should have taken pics when i was doing it, but the usual deal you just can't be bothered. That and the fact that you need to wash your hands first or the camera becomes an awfull black colour!
I'm really happy with it. It smokes when you rev it but thats just a small shot of smoke then clear. It does run a bit rough at idle but i think thats normal for a 3 cylinder and the fact its only held down to a sheet of chip board by 2 clamps. It does choof a bit of white smoke at startup when i don't glow it but when slightly warm, its clear.
I haven't run it long as i don't have any water hooked up. I am still trying to fit an alternator to it.
 

skidsteer.ca

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I'll try and post them tonight.
I really should have taken pics when i was doing it, but the usual deal you just can't be bothered. That and the fact that you need to wash your hands first or the camera becomes an awfull black colour!
I'm really happy with it. It smokes when you rev it but thats just a small shot of smoke then clear. It does run a bit rough at idle but i think thats normal for a 3 cylinder and the fact its only held down to a sheet of chip board by 2 clamps. It does choof a bit of white smoke at startup when i don't glow it but when slightly warm, its clear.
I haven't run it long as i don't have any water hooked up. I am still trying to fit an alternator to it.
Tazza
The d950 3 banger in my 553 has a bit of a odd vibration to, going on over 200 hours I've had it a no change so must be normal. Lots of white smoke with a 20 second or so crank time in 50 degree f weather without glowplugs. Glow plugs make it fire right up though.
So what hp is the 722? and sure send some pics for us
Ken
 

Tazza

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Tazza
The d950 3 banger in my 553 has a bit of a odd vibration to, going on over 200 hours I've had it a no change so must be normal. Lots of white smoke with a 20 second or so crank time in 50 degree f weather without glowplugs. Glow plugs make it fire right up though.
So what hp is the 722? and sure send some pics for us
Ken
Its rated at 18.5HP i believe.
I hope to attach it to a “ditch witch” trencher that has a dead engine. I was told i need 12-16 HP for it, so i hope this 18HP one will do the job. It just seems a little under powered for the trencher but i guess its geared rite down so it will have plenty or torque.
I did try and take some of the center main bearing shells but they didn't turn out well at all, just take my work that they were really sad. You can see the marks on the crank. The shells were deformed and the material was squished over the sides.
Now for piccies!
http://users.tpg.com.au/tazza_/D722/152_5202.JPG
http://users.tpg.com.au/tazza_/D722/152_5204.JPG
http://users.tpg.com.au/tazza_/D722/152_5208.JPG
http://users.tpg.com.au/tazza_/D722/152_5209.JPG
Those are direct links to show more detail.
152_5202.JPG

152_5204.JPG

152_5208.JPG

152_5209.JPG

I hope you all like my fuel tank :)
As you can see, its not really secured to limit vibration but it does the job.
It didn't come with an alternator so i fitted a Perkins one i had laying around. Seems to fit pretty well.
When it cranks you can really hear the compression. The only thing i really don't like is working out TDC and firing order. It has a mark on the flywheel for number one but not 2 and 3. I did manage to work it out i'm now going to stamp the flywheel! so next time its easier.
My air filter is a bit naughty i know.... It will have a proper one fitted before it goes into service, i promise!
As you can see on the piston, don't think you can keep using sad injectors. This is what you will do! this will cause lower compression and possibly a balance problem as the piston is being slowly melted away.
 

skidsteer.ca

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Its rated at 18.5HP i believe.
I hope to attach it to a “ditch witch” trencher that has a dead engine. I was told i need 12-16 HP for it, so i hope this 18HP one will do the job. It just seems a little under powered for the trencher but i guess its geared rite down so it will have plenty or torque.
I did try and take some of the center main bearing shells but they didn't turn out well at all, just take my work that they were really sad. You can see the marks on the crank. The shells were deformed and the material was squished over the sides.
Now for piccies!
http://users.tpg.com.au/tazza_/D722/152_5202.JPG
http://users.tpg.com.au/tazza_/D722/152_5204.JPG
http://users.tpg.com.au/tazza_/D722/152_5208.JPG
http://users.tpg.com.au/tazza_/D722/152_5209.JPG
Those are direct links to show more detail.




I hope you all like my fuel tank :)
As you can see, its not really secured to limit vibration but it does the job.
It didn't come with an alternator so i fitted a Perkins one i had laying around. Seems to fit pretty well.
When it cranks you can really hear the compression. The only thing i really don't like is working out TDC and firing order. It has a mark on the flywheel for number one but not 2 and 3. I did manage to work it out i'm now going to stamp the flywheel! so next time its easier.
My air filter is a bit naughty i know.... It will have a proper one fitted before it goes into service, i promise!
As you can see on the piston, don't think you can keep using sad injectors. This is what you will do! this will cause lower compression and possibly a balance problem as the piston is being slowly melted away.
Personally I would only use a 16 oz Budwiser King Can for a fuel tank. ;)
Ken
 

trg753

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LOL maybee next time.
If they even sold it over here.....
Good pictures! I had my 753 Bobcat smoking a bit and I pulled all the injectors and had them rebuilt at an injector rebuild place. They said they never saw such worn injectors and said it was a good idea to get them rebuilt. Seems like it was around $300 to totally rebuild them. It sounds much better now and starts good. Tom
 

Tazza

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Good pictures! I had my 753 Bobcat smoking a bit and I pulled all the injectors and had them rebuilt at an injector rebuild place. They said they never saw such worn injectors and said it was a good idea to get them rebuilt. Seems like it was around $300 to totally rebuild them. It sounds much better now and starts good. Tom
I think its something that is really over looked.....
Some people will get an engine re-built but not touch the injectors/pump. After seeing this damage i will make sure i keep an eye on them. The engines i have re-built i have made sure i got the pump/injectors done at the same time.
 

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