Kevin's M670 project

So I traded for this M670 diesel. I dont know much about it at all. From what I understood is that the clutch went out and then it was parked. The exhaust pipe and muffler are pretty rotten, so the engine is siezed. I've got it separated right now. Also have the engine torn down.

This is my first time working on a MM so I'll have some questions as I get it up and moving again.

So my problems right now are..

The piston is still stuck. It's been soaking in kroil for a few days.t's in my press now, but as you can see, a sleeve has moved before the piston wanted to let go. These are sleeveless engines so I'm not sure how to proceed from here.

The water pump was also locked up, but I've since cleaned it out and it rotates again

Not sure if the ampli-torque is working properly of if the shift forks arnt moving some gears around. Still diagnosing that one.

Also, I cant find any specs on a clutch disk. How thick is it new and what thickness is it time to replace? I dont know if mine was slipping because it's bad or it needed adjustment. It didnt grab at all while in gear. I tried rocking the engine to free it up and got nothing.

Edit.. I'm having troubles uploading pictures. Looks like ill have to do one at a time




















This post was edited by Kevinwterry on 12/11/2023 at 08:47 am.

I've never had to press a piston out of a sleeved bore before.

Is the piston below the sleeve and the sleeve below the bottom of the cylinder block at this point? If it is, I'd press it the rest of the way out. Then find a collar (or another cylinder block) to back up the sleeve and press the piston out of the sleeve.

Might want to try a few heating and cooling cycles to loosen the bond between the piston and sleeve before trying to press the piston out of the sleeve.


Good luck. Keep us posted.

Ya sorry for the duplicate pictures. I'll work on pulling some of those out.

I didnt realize the sleeve was moving when I was pushing the piston. I only noticed it when I had to reset the press for more throw. I had a 6x6x3/4 plate pushing down on a piece of pipe in the cylinder. It was blocking the view. Went from excited that what I thought was the piston finally letting go to seeing the sleeve moving. I dont quite understand. Its supposed to be a sleeveless engine. I cant find any replacements either. Was hoping I could just have the machine shop press a new one in.

I'll take another look at it when it when I get home. I think the piston is flush with bottom of the sleeve now.

They are sleeveless by design. However, many of them have been rebuilt using repair sleeves because of bore wear or other damage. I recently had to sleeve a bore on my G1000 Vista propane due to heavy corrosion from water sitting in the bore.

A machine shop should be able to fit a new sleeve in the block for you. Are any of the other bores sleeved as well?

So after looking closer, all 4 are sleeved. Should try to save this sleeve or is it junk? The piston did move, maybe a half inch. Sleeve moved 7/8".

You are in uncharted territory for me. I'd try and save it if I could. Then, have it measured at the machine shop for possible reuse. It would probably be good to have indexing marks on the sleeve and block if you try to reinstall the sleeve.

Be easier to find some good jugs/pistons than sleeving. Usually find oversize pistons and get bored. With a dry sleeve in MM no real way to pin it.

I have opted to sleeve a few blocks in the past. I had the machine shop bore from the top of the block and leave a shoulder at the bottom to prevent the sleeve from walking downward.

Ya I'll probably just push it out the rest of the way to see if the piston is usable. I'm sure the sleeve is too far gone anyways. I'll talk to a machine shop to see what my options are. Probably just find a new jug.

Anyways, does anyone have any specs on the clutch disk. All I can find is that its 12 inch. I need to know how thick they are new and what the wear limit is so I can see what condition mine is in. I'd like to put the tractor halves back together sooner than later.

Does anyone have a part number for the clutch alignment tool? The manual shows 10a12741, but nothing cross references to it? Or is there another trick to align it? I dont have a spare input to use either.

Kevinwterry said:

Does anyone have a part number for the clutch alignment tool? The manual shows 10a12741, but nothing cross references to it? Or is there another trick to align it? I dont have a spare input to use either.

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I always just eyeball it. Can get them pretty close by tightening pressure plate bolts just enough that you can still wiggle clutch disc to where it needs to be then tighten down fully.

What am I doing wrong here? I got the two halves finally back together, but the clutch isnt even touching the throw out bearing when the peddle is all the way down. It's almost at the end of the shaft it slides on. Somethings not right. I feel the pressure plate fingers arnt set right. I feel like I did it as the book said. The 13/32" doesnt seen correct. The throw out bearing would have to be at the end of the shaft to make it work.
The first picture is the peddle to the floor because theres nothing pushing it back, I assumed when I put the halves back together it would push it back to where It was close. Then I'd adjust peddle linkage to 1 1/2 free play.
2nd picture is when the peddle is all the way up.

My square is a hair under 2" so then I subtracted the 13/32 and set the t sqaure. I feel like I did what the book said but something isnt right. You would measure to the face that contacts the throw out bearing right? Not the back of the finger? But they seem like they need to come out another half inch or so.

Well I think I might have it figured out. I adjusted the peddle and I think its working. I didn't think I could get that much throw from adjusting the rod. I can grab the fan and rotate the engine and the tractor rolls forward, and I can have my 5 year old son press the clutch down and it let's go of the engine. Just doesnt feel right yet. So maybe some more adjustments after it's up and running. But that's a long ways down the road. At least it's back together for now.

This is a suggestion, and the risk should be all yours:

At this point, as far as the piston stuck in the sleeve goes, I think you are committed to pressing the sleeve the rest of the way out of the block. If the bore is that rusty mess in one of your pictures, the sleeve is probably un-useable anyway. Please note, there is the possibility of busting the cylinder bottom off the jug. But at least you could save the rod and possibly the piston.
There is also the thought of just pushing it down far enough you can saw the sleeve off above the top of the piston and getting a machine shop to finish cutting the sleeve out of the block.

If you know any machine shops close by, you might show your parts to them and get their recommendation. You will probably need their help in making it useable again anyway.

I live in the MM desert-North Carolina-and to fix one of these engines down here, sleeving them back to fit the piston is about the norm. There are no good MM parts sources closer than about 3 states away.

The machine shops I have used in the past usually put a shoulder in the bottom of the cylinder to keep the sleeve from moving while the engine is running.

Ya the piston stuck in the sleeve is fine. I ended up cutting the sleeve off that piston. Not sure why they didn't leave a shoulder for the sleeve. Anyways, the tractor halves are back together and the clutch is working as far as I can tell without running it

Okay, so now I've got everything back together except for the piston/cylinders. I figured I should start on the electrical side of it. I'm looking for a wiring diagram, only thing I can find is a picture from one forum on this site. It's a bit blurry when you zoom in. I printed it out and it's still hard to chase wires. I'm missing the key switch also. It should just be a simple on off switch, the starter is the type where you push the lever to start.

I'm not sure why they show some wires going into a wire loom. Makes it hard to follow. I cant read the small letters labeling the wires

Key switch made by Indak. Ignition and high/ low beam

Kevinwterry said:

So I traded for this M670 diesel. I dont know much about it at all. From what I understood is that the clutch went out and then it was parked. The exhaust pipe and muffler are pretty rotten, so the engine is siezed. I've got it separated right now. Also have the engine torn down.

This is my first time working on a MM so I'll have some questions as I get it up and moving again.

So my problems right now are..

The piston is still stuck. It's been soaking in kroil for a few days.t's in my press now, but as you can see, a sleeve has moved before the piston wanted to let go. These are sleeveless engines so I'm not sure how to proceed from here.

The water pump was also locked up, but I've since cleaned it out and it rotates again

Not sure if the ampli-torque is working properly of if the shift forks arnt moving some gears around. Still diagnosing that one.

Also, I cant find any specs on a clutch disk. How thick is it new and what thickness is it time to replace? I dont know if mine was slipping because it's bad or it needed adjustment. It didnt grab at all while in gear. I tried rocking the engine to free it up and got nothing.

Edit.. I'm having troubles uploading pictures. Looks like ill have to do one at a time

This post was edited by Kevinwterry on 12/11/2023 at 08:47 am.

Click to expand...

I notice this tractor and some M-602 tractors with cabs have a 2 piece hood with the joint just ahead of the gas tank. It appears well done. Was this a option on tractors with cabs or a farmer Modification?? Our M-602 ended up with a 2 piece hood but I was able to find a replacement. It was easier to work on with a smaller hood to remove>

cleddy said:

I notice this tractor and some M-602 tractors with cabs have a 2 piece hood with the joint just ahead of the gas tank. It appears well done. Was this a option on tractors with cabs or a farmer Modification?? Our M-602 ended up with a 2 piece hood but I was able to find a replacement. It was easier to work on with a smaller hood to remove>

Click to expand...

The M670s had this style hood. As far as I know all the M602s had the long hood like the M5 series. If it was changed more than likely a modification.