D722 complete engine rebuild

[TreeFarmer]

Hello,

New to this forum. I ran across this site from some YouTube videos posted over there.

So as my title says, I am in the middle of a complete rebuild on a Kubota D722engine. It was originaly out of a Club Car diesel powered UTV. No idea how many hours the engine had, but looks pretty clean so my bet is low. When I bot the engine it was cheap enough so I was prepaired for a complete rebuild. Sure Enough. After trying to start the engine I saw smoke/exhaust coming out from the head gasket so I knew something was up. Pulled the the head only to find a piston had a chip missing from around the edge and of course the cylinder wall was scored. After tearing the whole unit down, I noticed that the offending piston crank arm bolts were a bit loose. I suspect this is why the piston had it's problem. The head appeared all ok. Strait level and no damage. So I assumed this would be a good canidate for a complete rebuild. After all I did want use this engine to repower a piece of equipment on my Christmas tree farm. So I am just stupid enough to keep going. I have all the parts for the rebuild including a complete new gasket kit, new oversized pistons and rings. The block has been bored and I am putting it back together.

Disclaimer: This is my first engine rebuild. I have a shop manual, but it is less than perfect for a novice.

Here is where I stand. I have the crank in, but am now hung up on the rear main seal. On the crank, there is the main part where the seal goes around the crank which is about 10-12mm wide. Just to the outside of that is a slightly smaller/narrower neck about 5mm wide before the actual crank face. Sorry no picture. I can easily get the seal around this neck as it is about 2-4mm narrower in diameter than the wider part where the seal actually sits. But I can not seem to get the seal over the shoulders and onto the crank where it is suppose to go. Is there a special tool I am un aware of or does it just require a special technique unknown to the common man?

Help advice appreciated.

TreeFarmer

 

[dusty-t]

Surprised someone hasn't had an answer for you. I don't have the answer but this will get your problem to the top of the pile. Good luck. Dusty

 

[dusty-t]

Still no answers. The right guy still hasn't seen this yet. Dusty

 

[traildust]

Dusty Ditto

I think auquaforce has done a tear down

 

[TreeFarmer]

Thanks for the interest folk but I figured it out. After using brute force a little too much and ruining the seal. I got back out my parts schematic and there it was. There are two possible seals separated by serial number break. The nice lady at the parts house confirmed this for me. So as if turns out there is something to be said for brute force.

I will be back with updates and maybe more questions as I progress. Hopefully I will get some pictures up cuz that always makes a thread better. For now I wait two weeks for a part I will not be able to install for six weeks. Yes the harvest has already begun for the overseas shipments and the real crunch begins next.

TreeFarmer

 

[eserv]

Thanks for letting us know the problem! I have never had a problem putting the seals onto those Engines so was a little baffled what could be different about yours! Guess I've been lucky and always was given the correct seal. Maybe it helps that I look the parts up myself!:
Ed

 

[traildust]

TreeFarmer, thanks for the update and too bad you have to wait for that slooooooow boat

 

[TreeFarmer]

Just a quick update on the rebuild. I received the second replacement seal and again it was the same as the original only a different rubber material. I ended up destroying that one as well. I called the parts house here in the Portland area that I have been getting all of my parts from and asked to speak to some who could walk me through the technical problems I was having. I was armed with some inner & outer caliper specs for what the seal was suppose to be. After talking with the lead machanic at the Co., he switched me back to a guy on the parts desk. I was highly dubious that I would get the correct part, but he assured me this was the one.

Did I mention I am a complete novice when it comes to rebuilding engines?

He did have some good info for me and why the previous parts did not fit. It turns out there is a wear sleave pressed onto the crank. That explains why the first two seals fit nicely over the inital part of the crank but not the final part. Well the new (third) seal arrived via brown santa just as advertised on the day it was suppose to and fit like a glove. Unless I am missing something, they shipped me the seal completely free of charge as well. I guess it was their way of saying sorry for all the hastle I have gone through.

SO big thumbs up to EC Power Systems.

 

[TreeFarmer]

I am now deep into putting the engine back together. After getting the crank on, I attacked the pistons. All were labeled to their respective cylinders when i disassimbled the engine and placed into individual zip lock bags. I put the new rings on the new +0.25mm pistons and started putting them all back in. I did not change any of the bearing sleaves for the piston rods where they connect to the crank because everything worked normal before I took it apart and upon inspection everything looked fine with no real signs of wear. I also did not mic or have any work done to the crank so all those parts are the same. Again a visual of the crank did not reveal any notable wear. I decided to just take the gamble that all that stuff was ok, maybe not the smartest move, but again I am a rookie and this seemed like a resonable bet. After putting in the pistons, the engine was taking all of my strength to turn it over. I thought maybe this was because the pistons & cylinders were now so "fresh", things have just not worn in yet. I finished putting in all the front timing gears and sealed that cover all up. Last night I decided to take the pistons pack out and make sure I did not put the rings on wrong or screwed up in some other way. I have used a whole lot of assembly lube in putting this thing back together. After taking the pistons off, the crank turned freely by hand with very little effort. I know it should probably be a little stiff when turning the engine over considering the new pistons, but is there something I might be overlooking? Would using a little great on the sleaves/crank be ok? Is it normal to be this hard to turn over a new engine? I even gave my self one heck of a black eye when the wrench I was using to turn the engine over slipped off.

Adive suggestion appreciated.

Also once I get this resolved. I will quickly be moving on to the head. I beleive the manual says to use the copper spray, but I have read some information about how that is not necessary. Any thoughts or suggestions there?

Thanks Again
TreeFarmer

 

[fj40dave]

The tightness with the pistons installed might be due to their being .25 larger that what was originally in there.....just thinking out loud here.....but if you got .25 pistons and rings in the orig cyl holes.....things would be quite tight I would think.

The ease of turning the crank without the pistons attached sounds ok to me.

Wish you could shoot and attach some pictures ... they are always a help

 

[kuboman]

The tightness with the pistons installed might be due to their being .25 larger that what was originally in there.....just thinking out loud here.....but if you got .25 pistons and rings in the orig cyl holes.....things would be quite tight I would think.

The ease of turning the crank without the pistons attached sounds ok to me.

Wish you could shoot and attach some pictures ... they are always a help

Just to expand on this. To put in oversized pistons you would need to have the cylinders re-bored. If this is not done then you will have serious wear if you can even get it to run. I am surprised you could even get the pistons in the cylinders.

 

[SpudHauler]

You need to have a machine (engine) shop check your piston to cylinder clearance and bore the cylinders for the new pistons. They will need to know the clearance and then you should be fine.

You never put 25 over pistons in stock cylinders. Even if they did fit, it would mean the cylinders are in desperate shape and the rebuild would only last hours if it would even start.

Added; Guess KuboMan and I were writing at the same time.

 

[kuboman]

Added; Guess KuboMan and I were writing at the same time.

Great minds think alike!

 

[fj40dave]

I just completed a rebuild on a D1301-A (L295DT motor).....I dropped one of the pistons and broke the skirt, so I replaced it.
Putting new rings on the pistons, new rod bearings, and lightly honed the cylinders was all I needed to do.
The motor runs awesome now.

Is that something you could get by with....using stock size pistons/rings, and a light hone for the one that has a light scoring?

Dave

 

[TreeFarmer]

Right, wrong or what have you, I started to re-install the pistons. Two went in fine the middle piston had a problem. I ended up ruining the bottom ring on the piston. Doh! I must say even though I had to order a new ring set today I am glad I stopped to re-install the pistons. I am not sure exactly what the problem was but things are much smoother now. I known not all the pistons are in but it is already the motor is easier to turn over. I think maybe I had the bottom part of the conecting rods turned 180 degrees off. A small film of grease and some assembly oil on the crank when assembling and these two pistons are now turning over by hand. $54 for a new rings and I still feel good about stepping back and starting over.

TreeFarmer

 

[fj40dave]

You GOTTA have the video camera runnin when ya fire this off for the first time!!!!
I wish I had had one set-up when I fired off my last rebuild....it was so sweet!

 

[TreeFarmer]

Thanks for all the responses, must confess I missed them all before I started work last night. As previously posted, I did figure out my issue and things are working as they should.

Rest assured, I am a newb but not so much as to know that I needed to have the engine bored out before trying to put in oversized pistons.. There was some scoring on one of the cylinder walls which was the basis for even starting down this whole path. I knew I needed professional advise I could not get from the web. So I took the engine, head removed, to a VERY reputable engine machine shop they recommended boring it out. After I tore it apart and took it back to them, they wouldn’t even touch my block until they had one of the new pistons so they could make sure they had it correct. These guys work on everything from race engines and big semi rebuilds down to 1 lung Yanmar L100 engines. They know what they are doing and did a very nice job.

I will get some pics & video soon.

TreeFarmer

 

[SpudHauler]

That is good TreeFarmer being a newb and all. You are tackling something a lot of people would shy away from.

Anyway, when you take crank/rods apart like that, the norm is to put a punch mark in each cap and rod so you can match marks later on re-assembly. Bag each, like you did and number them front to back, whatever works for you. And, all marks are on the left or right side, so the rods go back in the same direction with the caps in the right way. That a heads up.

Now as far as the crank is concerned and it's clearances with the rods, unless you are real sure they are in good shape, you should check with plasti-gauge. Actually you should check anyway. Because if they are at the limit of wear and you are installing a new fresh top-end, the new load on the crank will wear things that much faster. A year down the road, you now have a crank making noises. You've gone to far to have that happen. Talk to your machine shop and they will give you tips on measuring the clearance. Better to be safe than sorry.

The other key here is the head and making sure it and the cyl are flat and smooth, no cracks and good valve sealing. Quick check, remove the cam, place head upside down, fill head/valve are with gas and see how long it takes to leak out. Real fast means valve job required, one fast means valve job, all slow = sweet , carry on.

On last note, now is a good time to verify that every oil passage way is free and clear, no gunk. And on assembly don't use tons of gasket sealant it just increases the chances of plugged oil galleys.

Good luck, take your time, ask questions and keep us posted.

PS: Remember, the little bit of time spent now, will result in years of enjoyment later.

 

[TreeFarmer]

Anyway, when you take crank/rods apart like that, the norm is to put a punch mark in each cap and rod so you can match marks later on re-assembly. Bag each, like you did and number them front to back, whatever works for you. And, all marks are on the left or right side, so the rods go back in the same direction with the caps in the right way. That a heads up.

The marks were there. I initially was working off a diffrent reference point and that was clearly wrong. But this is a great tip and I will remember it next time. When I disassembled the engine I did take my sweet time and used a lot of zip lock bags and a good sharpie. I knew this project would test my skills and I did not want to screw up anything. Another good tip for the next newb would be to take pictures as you go along. before you disassemble and of the bag the parts went in. Keep the pictures in order and then follow along as you reassemble only in reverse order.

Now as far as the crank is concerned and it's clearances with the rods, unless you are real sure they are in good shape, you should check with plasti-gauge. Actually you should check anyway. Because if they are at the limit of wear and you are installing a new fresh top-end, the new load on the crank will wear things that much faster. A year down the road, you now have a crank making noises. You've gone to far to have that happen. Talk to your machine shop and they will give you tips on measuring the clearance. Better to be safe than sorry.

yeah this is the only real area where I felt I would be taking a gamble and you are confirming my suspissions. My brother mention somthing about the Platiguage material the other day. Since I now have to wait for new rings to show up, I will see if I can find some and check.

The other key here is the head and making sure it and the cyl are flat and smooth, no cracks and good valve sealing. Quick check, remove the cam, place head upside down, fill head/valve are with gas and see how long it takes to leak out. Real fast means valve job required, one fast means valve job, all slow = sweet , carry on.

I have check both the black surface and head and they are flat all 6 ways. I am very comforable with this. The tip for checking the valves, a big thumbs up to you. I will give that a try for sure.

On last note, now is a good time to verify that every oil passage way is free and clear, no gunk. And on assembly don't use tons of gasket sealant it just increases the chances of plugged oil galleys

.

The machine shop dipped the engine and blew out all the ports & holes when they did their work. The block came back sparkly clean. I spent a fair amount of time stripping of the old seal material and cleaning the rest of everything. Always good to point this out though.

So far I have used what looks like an appropriate amount of sealant about 2-3MM line as recomended by the manual and have been especially careful around ports but again it's good to be reminded and mindful as I proceed forward.

These are good helpful and constructive tips. Thanks much for the input. Half the reason I started this thread was for those that may attempt a rebuild like this and would like a reference point for review. I do like creating resources like that. A few years ago, I installed a decomissioned flatbed railroad car as a bridge on my farm. I took good notes lots of pictures and then wrote an extensive write up about it and posted all this to our farm website. I have had a few questions about it from others who were thinking about doing the same thing.

Thanks Again
TreeFarmer

 

[kuboman]

Thanks for all the responses, must confess I missed them all before I started work last night. As previously posted, I did figure out my issue and things are working as they should.

Rest assured, I am a newb but not so much as to know that I needed to have the engine bored out before trying to put in oversized pistons.. There was some scoring on one of the cylinder walls which was the basis for even starting down this whole path. I knew I needed professional advise I could not get from the web. So I took the engine, head removed, to a VERY reputable engine machine shop they recommended boring it out. After I tore it apart and took it back to them, they wouldn’t even touch my block until they had one of the new pistons so they could make sure they had it correct. These guys work on everything from race engines and big semi rebuilds down to 1 lung Yanmar L100 engines. They know what they are doing and did a very nice job.

I will get some pics & video soon.

TreeFarmer

It sounds like you have done your research. I apologize for inferring that you did not know what you were doing
Good luck with the rest of it. It will run like a top.