M18 or M20 rebuild $ and hours used?

[clay1811/44c]

Okay for those of you that rebuilt or bought a rebuilt M18 or M20 how much did you spend? Then how many hours did you get out of the rebuilt engine? I like to keep things original, but I may just repower.

[john hall]

M18 out of my 1811
I didn't split the cranckcase, just top end.
Grind the valves, $50.
Bore was still in spec so I didn't have to bore jugs, just hone.
Aftermarket gasket kit with seals, about $50.
Aftermarket piston/ring sets, around $120-150.
High temp spray paint $4.98
Service manual, about $25.
I changed the fuel pump because it was OLD, about $40 aftermarket

I can't remember if I measured the valve stems, but the guides seemed a little loose. I don't think the machine shop checked these. I know the shop quoted me another $40-50 to bore the jugs, don't know what guide replacement would have been.

My "guideline" for this project was that we have 4 other mowers ready to go. No need to sink a mint into this one, considering it will only run 40-60 hours a year. Although dad seems to be liking this one a lot and leaving the 2 Supers under the shed lately. Maybe that will change when the new wears off. The reason we went into the engine was I had a miss we couldn't get out and were blaming it on a valve after checking spark, intake leaks etc. Turns out something was up with the carb, it had been tinkered with before I got the mower--don't know if the guy drilled something out or if there was crap embedded inside I couldn't get out (failed to pull welch plugs--I know better know). Anyway, old engine wasn't smoking or knocking. So far we only have about 10 hours on it, doing fine.

Would I do it again, absolutely. If it were my 2072, then it may get genuine Kohler parts and quite possibly split the case.

[J-Mech]

John, I know you spent a ton of time on that engine, but if you didn't split the crankcase, replace the rods and grind the crank, or even bore it, you didn't rebuild it. You just repaired it. Not being a jerk, but that's the truth. You really only fixed it, not rebuilt it.

[dvogtvpe]

I call them "patch jobs"

[Mike McKown]

My neighbor "redid" his M 18 the same way John described.

The engine was in a late '70's/early '80's Bolens that had cut a "lot" of grass up and down steep hillsides. It started smoking while running.

I have no idea how much $$$ he had tied up in it but it ran well for at least ten years after his "redid". He got a new Scag and gave the Bolens to a relative. It may still be running.

[john hall]

Originally Posted by J-Mech

John, I know you spent a ton of time on that engine, but if you didn't split the crankcase, replace the rods and grind the crank, or even bore it, you didn't rebuild it. You just repaired it. Not being a jerk, but that's the truth. You really only fixed it, not rebuilt it.

Agreed. That's why I went into detail about my intended use (amount of hours). It should run for quite some time, assuming nothing flys apart. I really think the valve guides have excess clearance. A full rebuild would have included changing them, changing the rods, grinding crank if needed, and testing and replacing valve springs. I did forget to mention I lapped the heads on a surface plate--one had to be faced on a mill. I did this myself, so nothing but labor involved, no $.

These engines are about like any other, when you open it up then you'll know what you have to have. Kind of like taking a 4 cylinder tractor head in to be faced and valves ground. Two days later you get a call the ONLY thing useable is the head and valve keepers--everything else is shot, BTDT.

[ol'George]

I guess it depends on what you find when you open them up.
about 900+ hours ago I opened up a m-18 from a $200 1720 cub.
Everything looked good inside, I junked the cub saving only what I thought I might need in the future,as the hydro was junk.
the crank/rods measured good as did the bores.
I touched the valves up/set clearances, replace the seals on the crank as well as on intake valves as they were as hard as a wedding night groom.
While apart I converted it to a horizontal engine.
but that is another story.
I wish I knew the hours on it originally from factory but I don't.
I can attest it has 900 + hours on the conversion with no problems other than needing a needle/seat in the adjustable carb.
I did replace a mag coil some years ago.
To me I like smoothness/ torque and sound of the opposed twin.
Yes it uses a little more fuel than a modern OHV fool injected emission engine.
As far as I'm concerned the m-18 is good & dependable if given an oil change every 50-100 hrs and keeping the pre foam air filter regularly serviced/oiled
I use a tank & 1/4 of fuel every mowing on the 782 but I do mow a lot of grass.
You won't get any complaints from me on those opposed twins.
They got a bad rep because of the series 1 oiling system design, but that was all fixed on series 2 and later, as was improvements in crankcase strength, larger flywheel taper, *30 valve angle and crankcase breather.
The only negatives I see are cost of parts are high from mother Kohler but still can get reliable aftermarket ones @ lesser cost.
Some are NLA, but ebay will provide alternatives that are NOS at times.

[Oak]

Originally Posted by dvogtvpe

I call them "patch jobs"

Yep, and sometimes that's all you need.

Why blow $1500+ on a repower or a rebuild when you don't need to? Oh sure, I wouldn't recommend John go start a landscaping business and run his Mag 18 200 hours a week but if all your going to do is run it every now and then I don't see an issue with doing what he did.

When I rebuilt my Onan I could have saved a lot of money by dropping a new 23 Vanguard or CH20 in it but it wouldn't be correct. Will I do it again, yes, I have 2 more 982's that need their B48G's rebuilt.
I look at it like pulling an engine out of a 69 Z28 and dropping a new crate engine in it. Yep, it's a lot better engine and has more power but it ain't correct.

That is my

[Mike McKown]

Originally Posted by Oak

Yep, and sometimes that's all you need.

Why blow $1500+ on a repower or a rebuild when you don't need to? Oh sure, I wouldn't recommend John go start a landscaping business and run his Mag 18 200 hours a week but if all your going to do is run it every now and then I don't see an issue with doing what he did.

When I rebuilt my Onan I could have saved a lot of money by dropping a new 23 Vanguard or CH20 in it but it wouldn't be correct. Will I do it again, yes, I have 2 more 982's that need their B48G's rebuilt.
I look at it like pulling an engine out of a 69 Z28 and dropping a new crate engine in it. Yep, it's a lot better engine and has more power but it ain't correct.

That is my

It's like most decisions.

It depends.