New 682 (I may have a problem)

[J-Mech]

Thanks for the compliment.
Don't forget George though. He knows more about the KT/Mags than I do. Glad he knows if the rod/piston combo will interchange. I assumed they would, but could not confim.

Yeah, the '82 series didn't follow all the previous model designation. It does get more confusing.

I agree that the Mag 18 and the KT II is basically the same. No real parts or longevity diffrences.

[Gompers]

Originally Posted by ol'George

To answer your piston/rod ? yes rod/piston from m-18 will work.
The pix of your crank is positioned so I can't see the cross drilled rod oiling holes,are there there?
Just checking that some PO didn't slip in a series 1 crank.

99% sure they are. Will look when I get home.

That would sure make a rebuild more palatable.

[Gompers]

Crank definitely is a series II. Been trying to find a machine shop. Been a while since I did any serious engine work, and the one I used to go to is sort of not around anymore. The places that have a grinder in house want ~100-150 bucks to grind it, and that's a little high, IMO.

Looks like I have the Mahle pistons too. Measured them again, and they are both within .001 above the max wear spec. Very tempted to just re-use them. M18 pistons are a lot more palatable than KT17II ones price-wise though, and I already need new rods. A little scuffing on one of them, but nothing too awful.

I guess it would be peace of mind to know it's all new, but that's 140 bucks I could spend on other things this tractor also needs.

On the plus side, I cleaned up the valves tonight and measured the stems and the valve guides and they all look to be in spec with minimal wear. Valve margins and faces all look good. Seats look to be ok, but still need to clean them up a bit more to be sure. It's been super cold here, so I've been doing all this in my mostly-finished basement and I'm trying to avoid getting out the super stinky stuff for cleaning.

[Marko141]

Definitely don't wanna be outside these next few days. It's going to be -30 here.

[ol'George]

Ya, those are the later Mahle/forged ones.
Shoot some pix of the skirts both sides, and the ring area, above the rings, on the skirt side,
if the ring side clearance is not wallowed, they will probably be OK. Unless the area above the top ring is scuffed off.

[Gompers]

Originally Posted by ol'George

Ya, those are the later Mahle/forged ones.
Shoot some pix of the skirts both sides, and the ring area, above the rings, on the skirt side,
if the ring side clearance is not wallowed, they will probably be OK. Unless the area above the top ring is scuffed off.

wellll.....
Tried to highlight the worst spots on both of them.

Here's #1





Here's #2

[ol'George]

Not liking what I'm seeing.
I'm thrifty but those pistons show scuffing above the rings and an abnormal wear pattern.
Usually the scuffing on the crown edge is inline with skirt, those show some almost above the pin area, like the rod was bent or the jug/cylinder was not parallel with the crank.
Not a normal wear pattern.
Investigate the block more, was it blown up once before?(Nicks/dents inside)
What did you find in the crack down the side? was it a crack or just a witness mark from a cracked casting die that made it??
I would replace the pistons, and look for the reason of the unusual wear pattern.
Might prowl ebay for block and crank.
When I last looked there were several good used assy's and not over priced.
A good block will be $100 shipped, about the same for a crank sometimes they will throw in a good set rods and or pistons.
I built a good mag 18 engine a couple of years ago from parts, think I had $4-500 in it when done.

That included rings, valve job seals /gaskets, new gov gear, course it was all my free labor so no cost there.

[Gompers]

Originally Posted by ol'George

Not liking what I'm seeing.
I'm thrifty but those pistons show scuffing above the rings and an abnormal wear pattern.
Usually the scuffing on the crown edge is inline with skirt, those show some almost above the pin area, like the rod was bent or the jug/cylinder was not parallel with the crank.
Not a normal wear pattern.
Investigate the block more, was it blown up once before?(Nicks/dents inside)
What did you find in the crack down the side? was it a crack or just a witness mark from a cracked casting die that made it??
I would replace the pistons, and look for the reason of the unusual wear pattern.
Might prowl ebay for block and crank.
When I last looked there were several good used assy's and not over priced.
A good block will be $100 shipped, about the same for a crank sometimes they will throw in a good set rods and or pistons.
I built a good mag 18 engine a couple of years ago from parts, think I had $4-500 in it when done.

That included rings, valve job seals /gaskets, new gov gear, course it was all my free labor so no cost there.

As for the crack, I still don't know what to make of it. I took a bit of sandpaper to it to see how deep it went, and it's not real deep, at least near the bottom.

Near the top, there's more material (it feels like more casting material), but it's also in a thick part of the casting.




There's no sign of a crack in those areas on the inside of the casting


I did see a nick here or two inside the case. You can see it in that last picture there near. Other than that, I don't see any nicks or gouges in any of the castings. Pretty sure it has been apart before. It was all black RTVd back together (jugs and closure plate).

[ol'George]

Guessing if it was blown up before, and possibly bulged the crankcase 1/2, in the crack area, causing the crack on the outside but not inside.
Did the piston that had the abnormal wear pattern near the pin, come from the crack side? If so, that would explain the abnormal wear pattern.

Wet the block crack area with any solvent, Kero or diesel etc, and dry it with towel, Then tap on either side of crack with small hammer.
if crack is all the way through the casting they will usually weep solvent from the crack, and you can see it clearly.

Gut feeling is the block is hurt, maybe not cracked through, but hurt.
If it were mine and I was not in a hurry, I scurry parts from ebay and slowly
built a good engine from good usable parts.
They are out there or as some do, repower with newer OHV stuff.

[Gompers]

Originally Posted by ol'George

Guessing if it was blown up before, and possibly bulged the crankcase 1/2, in the crack area, causing the crack on the outside but not inside.
Did the piston that had the abnormal wear pattern near the pin, come from the crack side? If so, that would explain the abnormal wear pattern.

Wet the block crack area with any solvent, Kero or diesel etc, and dry it with towel, Then tap on either side of crack with small hammer.
if crack is all the way through the casting they will usually weep solvent from the crack, and you can see it clearly.

Gut feeling is the block is hurt, maybe not cracked through, but hurt.
If it were mine and I was not in a hurry, I scurry parts from ebay and slowly
built a good engine from good usable parts.
They are out there or as some do, repower with newer OHV stuff.

That was the #1 cylinder, and the crack is in the #1 side of the crankcase. So that may explain that.

I think I'm probably going to do as you said, and dig up some parts here and there, or keep my eye open for a replacement that's in better shape.

Thanks George. This place is an invaluable resource!