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M-12 Engine rebuild

Afrakes

Sustaining Member
Finally got the engine up and out of the boat today. I had broken it down a few weeks ago and took advantage of the above freezing weather (soon to be gone) to get it into the shop.
 

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Afrakes

Sustaining Member
M-12 rebuild

Had an over heat event the season before last. Engine ran fine afterward with no problems. This past season an excess crankcase pressure problem developed though the engine continued to run start and run fine. I suspect a head gasket issue but with the engine being thirty years old I decided to break it down and take a thorough look. It needs cleaning and painting as well. I'll let you know what I discover.
 

Afrakes

Sustaining Member
Rebuild Update

Finally got the block, head, crankshaft and camshaft back from the machine shop. The guy I used is a one man outfit and rebuilds just about anything including racing engines. My little job kept getting put on the back burner. More than satisfied with the work and the price in the end. $200.00 for all he did.

The crankshaft was well within specs so all he did was polish the journals. The same with the camshaft. The head was .005" out of flatness so he milled that down and reseated the valves. Luckily valve guides and springs were all within spec.

The block ended up having to be bored. This engine sat unused for five years. When I pulled the head I discovered there was corrosion on the number 2 cylinder liner. Number 1 liner was fine. I suspect that the exhaust valve on number 2 had been open and moisture got in there and corrosion developed between the rings and liner. Instead of getting the liners pressed out and new ones machined, installed and bored I decided to go for oversize pistons. The pistons, while more pricey than the liners, kept the overall labor costs down.

I also had the shop press the front main bearing into the block. The same with the wrist pin bushings.

All of the rebuild parts, gaskets, bearings, pistons, were sourced through a local Kubota dealer. I found an excellent reference online that gave me all of the Kubota part numbers. That made communications with the local dealer much easier. Unfortunately there are no pre-packaged rebuild kits available for the Z400. As a result I had to pour over all of the illustrations and identify each and every part I needed. Only took me three tries to get them all.

Since I'm totally going through this engine every part was removed, stripped, cleaned and painted. Raw and fresh water pumps are new. Glow plugs are new. Injectors only have 900 hrs. on them and were working fine so I'm leaving them alone.

So now comes the fun of reassembly. I've got my 10 year old grandson interested and he's going to give me a hand. I will total up all of the costs and post that when things are complete.Engine parts.jpg
 
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Afrakes

Sustaining Member
With a little help

After chasing all of the threaded holes in the engine block with the proper size taps grandson Jonathan and I installed the new shell bearings and pistons on the connecting rods.

We also ran proper sized drill bits into all of the through holes of the various engine parts to make sure that they were ready to assemble.

We then installed the valve and fuel cams and oil pump on the block.

We're awaiting delivery of the correct No. 1 main bearing for the crankshaft. Hope to have it this week so we assemble everything over the next weekend.Jonathan and Al III.jpg
 

Red Squirrel

1985 Ericson 28-2 Hull# 607
Z400 documents and part source

Could you share where you get your Z400 parts online along with the drawing package you mention?

I need to do work on my M-12 but I’ve had no luck finding the Kubota Z400 information and good part source.

Thank you,
Joe
E-28
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
About the reply #6 picture, any number of captions might do, and all end up with the word "Priceless!"
:egrin:
 
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
This thread makes me want to buy an old diesel, take it apart, put it back together, paint and polish, and then mount it on a stand in my living room.
 

toddster

Curator of Broken Parts
Blogs Author
This thread makes me want to buy an old diesel, take it apart, put it back together, paint and polish, and then mount it on a stand in my living room.

You can have my "extra" Atomic 4 if you like. Picked it up a couple of years ago at a local garage sale because, well, somebody had to save it from the scrap yard. But the last thing I need at this point is another project.
 

Afrakes

Sustaining Member
In the living room

Many, many years ago I lived in a house with five others college age guys. I had a great aunt whose last name was Tilley. Aunt Julie Tilley had a bad habit of just dropping in whenever she and Uncle Jimmy were passing through. She arrived unannounced one afternoon to find a partially disassembled motorcycle in the living room as well as a Volkswagen Beetle engine sitting on the coffee table. Needless to say she didn't stay long. She never did, as all of the arm chairs had very dirty and sticky arms. 95' Yanmar 2GM20F next in line to rebuild. Want a piece of the action Christian?PICT0216.jpg
 

toddster

Curator of Broken Parts
Blogs Author
I seem to recall a guy in college who used the aluminum head of his Datsun engine, and other bits and pieces, as decorative wall hangings.
 

Afrakes

Sustaining Member
Final Accounting

I added up all of the costs associated with the rebuild and re-install. Includes cost of item, shipping and sales tax.

Engine rebuild related: parts, gaskets, machine shop, etc. $1,614.17

Misc.: Paint, sealants, tools, etc. $ 287.83

Extras: New fresh and raw water pumps, engine mounts, prop shaft, stuffing box, control cables, wiring, etc. $954.23

Yes, it took many personal hours to remove the engine, break it down, identify, label and organize all of the parts. Research a source for identifying the Kubota parts. Finding a local source for those parts. Clean and paint all of the parts. Then assemble everything and re-install the engine with the extras. As I'm self-employed and my slow season runs from Jan. to May I had the time to do all of this. A luxury that most folks don't have. Also, being in the northeast and having many months between sailing seasons meant that the boat was on the hard. I keep it at home so it was convenient. Sure, I would have preferred to purchase and install a brand new engine but it was not in the economic cards for me. I will shortly be back on the water with a reliable back up of propulsion at a cost I could afford. I'm very happy with the outcome and had a good time sharing some of this with my youngest grandson. Correction, my second youngest grandson. The one and a half year old wasn't interested. This chapter of life is over.
 
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