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dgjks6

k181 rebuild

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So the winter is here and the wheelhorse bug is back. I am going to rebuild a k181 for my c-85.

For those of you new to my life, I got a c-85 with a blown motor and have not had the guts or time to rebuild, but now I have a 416-8 that I need to take the motor out of, so I am going to finish this kohler first - and then move into the 16hp monster.

So let me start with what I've got:

DSCF6138.jpg

Its all moved into the basement when its warm. I'd like to have everything I need for reassembly by the week after christmas when I am taking a week of vacation - and I want to put it together then.

I know an engine rebuild for many of you is a day job, but here at casa de Kovacevich I hope to have it done by early spring.

So here is where I am at so far:

engine half disassembled. Then rod and cam shaft were broken. I just bought a rebuild kit on ebay. It looks to be half stens and half kohler parts. Piston ordered is .010 over. From wha tI can tell the engine has never been bored out. When it comes I need to find somewhere to bore it out.

The crank journal was nasty. I found a place that grinds cranks for $90, but they want the rod before they will do it. the rod I ordered was .010 under.

So now for the questions and the continuation of my luck. When I was move the new camshaft I ordered over a year ago, I dropped it and this was the result (I think - I hope this is not the old one which was broken and I lost the new one)

DSCF6139.jpg

So can I order any camshaft for a k181 - or were there specific ones for a wheel horse, for example:

http://cgi.ebay.com/KOHLER-CAMSHAFT-K181-8...=item33630d315a

Next - when I took off the bearing plate I cracked it - I got another one (actually 2 - bearing plates are not universal to all k181's - Anyone want to buy a bearing plate for a k181 from a JD?)

So how do I get this out:

DSCF6140.jpg

Last question. Got lots of bearings now - from the bearing plates I ordered - How do I tell if they are still good? Don't want to order anything I don't have to.

Greg

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Well, learned that the cam shaft I dropped was indeed the new (old) one. The other was still in the block.

I took every piece off the engine except I can't fingure out how to get the valves off.

Also, I see a few NOS cranks on ebay. They look rusty. Wonder if I can get the rust off without changing the grind of the crank and just use a standard rod?

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You might be better off to buy a used motor for parts, I bought a good runner for 50 bucks off ebay

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I keep thinking about things like that, but I have this hoarder thing issue. I can't do things for parts. I feel like if I have a parts engine then I have to fix it, eventually - it will sit on the shelf until I get to it. Which in some cases may be forever.

Also, if I get a used block and crankshaft I would still probably have them machined and checked anyway, unless they are NOS, which from the prices I see are more then machining the ones I have.

I do realize it would be cheaper and quicker to buy a rebuilt k181. There is a place in Minerva that I can buy a rebuilt k181 for around $500 - then just paint it, transfer the shrouding, carb, PTO, and be ready to go in a couple days.

That would be cheaper and quicker and make more sense.

And then selling all of my wheel horse stuff and only keeping what I need and use would be the smartest thing to do. And right after that my wife is going to go through her shoes and only keep the 10 pairs she uses and gets rids of the rest. Then my kids are only going to ask for what they need - and be happy with what they have. I better stop now.

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LOL @ the hoarding, I only have 3 extra 10hp, 1 12hp and an extra 7hp

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Hey there is a used crank on ebay right now going for 8 bucks, sellers name is kellysells parts, is that our Kelly here. 12 hours left

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my k181 8 pony is done i just need to go get it at the machine shop. i bought all new kohler rebuild kit and that set me back a few months. i got all the attaching parts painted. buffed up the head . this is for my 1976 b80. now i gotta get a few more bucks saved and go get it :ychain:

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OK guys how close do the tolerances have to be?

My micrometer measures to .001, but some of the measurements in the specs go to .0005. Do I need a new micrometer.

Now for the real questions. As you know I bought a rebuild kit on ebay.

So when measuring the piston I say you measure at the bottom and just below the rings. Here are my measurements (I am leaving off the 10/1000th place because I can not measure it):

Just beow the rings:

Factory Spec: 2.928 to 2.929

Old piston: 2.918 to 2.920 (range of measurements around piston)

New piston (.010 over): 2.920 to 2.930 (range of measurements)

Bottom of piston:

Factory specs: 2.932

Old piston: 2.921 to 2.922

New Piston (.010 over): 2.926 to 2.935

First deduction - original piston is worn below factory specs so it needs replaced.

So my question is WTF? It seems the piston I got is out of round and not a full .010 over.

Am I being too anal? Is this normal? Should I break down and get a kohler piston?

I am waiting on the inside bore measuring device. I would like to take to the machine shop, I just want to make sure I got the right pieces.

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OK guys how close do the tolerances have to be?

My micrometer measures to .001, but some of the measurements in the specs go to .0005. Do I need a new micrometer.

Now for the real questions. As you know I bought a rebuild kit on ebay.

So when measuring the piston I say you measure at the bottom and just below the rings. Here are my measurements (I am leaving off the 10/1000th place because I can not measure it):

Just beow the rings:

Factory Spec: 2.928 to 2.929

Old piston: 2.918 to 2.920 (range of measurements around piston)

New piston (.010 over): 2.920 to 2.930 (range of measurements)

Bottom of piston:

Factory specs: 2.932

Old piston: 2.921 to 2.922

New Piston (.010 over): 2.926 to 2.935

First deduction - original piston is worn below factory specs so it needs replaced.

So my question is WTF? It seems the piston I got is out of round and not a full .010 over.

Am I being too anal? Is this normal? Should I break down and get a kohler piston?

I am waiting on the inside bore measuring device. I would like to take to the machine shop, I just want to make sure I got the right pieces.

For the money my kohler k181 kit was 400 bux yea i know, but i wanted to stay original. i got a piston .010 over and new upgrade rod them old ones came apart alot lol. take it to machine shop let them do all the grindin honin and stuff you`ll thanks yourself. then you can assemble the rest just a thought. :ychain:

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So my question is WTF? It seems the piston I got is out of round and not a full .010 over.

Pistons have to be smaller at the top to compensate for thermal expansion. They are also cam ground which makes them elliptical (up to .015" larger when measured across the skirt @ 90 degrees to the pin bore - known as the thrust face) for the same reason.

Normally, the larger the piston, the bigger the difference between the two measurements.

You also have to subtract up to .020" of running clearance when measuring a piston at it's thrust face. The piston and the bore can't be the same size (or too tight) or it will seize up almost immediately. (There has to be room for a coating of oil to remain on the cylinder wall)

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So if I read that right, the elliptical shape is OK.

So what I need to do next is wait for the cylinder bore calipers to arrive, measure that and compare it to the size of the piston.

The Factory Spec bore is supposed to be 2.937 to 2.938 with a piston that measures 2.929 on the trust face for a difference of about .09.

So if my cylinder measures 2.940 I am golden because the thrust face on my piston measures 2.930. Or else I need it bored out to that.

So there is a chance I may not have to see the cylinder man.

After I get this settled, I will move on to the crank.

Does this make sense to anyone?

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The standard (new) bore size of the K-181 is 2 15/16" or 2.9375"

.010" over size would mean that the finished bore size needs to be 2.9475"

If you bought the correct +.010" piston, the finished bore size is all you need to be concerned with.

This is why all measurements need taken and required machining should be performed before the parts are purchased. If the bore in the block you have is already at 2.940" and is excessively out-of-round - or has a scratch deeper than .004", (a little more than half of the .0075" needed to get to the next oversize) it won't "clean up" and you'll have to go to .020"

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I'm learning as I go. I don't know a small engine shop so I called an auto machine shop near my house and they told me to bring in the piston and the block and as long as its over 2 inches they can do it.

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OK - I think I got it all figured out. Found a guy here is Akron at NorthHampton Crank that will turn the crank and bore the cyliner for about $100. He has all the specs for the kohler engines and will bore the cyliner the smallest amount needed. I got my fingers crossed that I will be able to use my .010 piston. If not I can always make a lamp out of it.

For the crank - he said that the rods from Kohler or aftermarket are sometimes off, so he will measure the rod and then turn the crank to the correct size for the oil gap. He also said he can turn it .030 under and bore out the rod so I can put bearings in it if I want. He does a lot of work for pullering tractors.

The down side is that he said the turn anound is 2 weeks because he is swamped this time of year.

Patience is a virtue.

So now that I got this sorted out, I am onto the valves. How important is it to check the valve guides and all of that? I see lots of videos on the net about rebuilding kohlers, but no one ever talks about valves. They just seem to put the old ones right back in.

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If the guides are worn you need to address them also, otherwise you will use oil. Take the valves to the machine shop and he can measure them

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He also said he can turn it .030 under and bore out the rod so I can put bearings in it if I want.

As far as I know, that can only be done on the 10 thru 18hp singles.

I don't know of any bearing inserts small enough to fit the 6/7/8hp rods, so you're stuck with standard or .010" under - unless you have the rod resized.

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Didn't tell him it was a k181, just told him it was a single cylinder kohler. Think he can still do the bore and crank or should I call and ask him before I go out there?

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Yeah.... a phone call is much cheaper than gasoline. :ychain:

My local machine shop's theory is "if we can hold it (clamp it down), we can bore it".

It's hard to tell on the crank grinder though. Some machines/shops aren't capable (or don't really want to mess with) the smaller jobs.

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If the bore in the block you have is already at 2.940" and is excessively out-of-round - or has a scratch deeper than .004", (a little more than half of the .0075" needed to get to the next oversize) it won't "clean up" and you'll have to go to .020"

Just to add to what Terry said...

Boring a cylinder .010" over means that they are only taking .005" off each side of the bore. So any wear or scratches on one side of the bore need to be less than .005 deep...

In actual practice you can offset the bore a couple of thousanths to account for this, but keep it in mind.

A lot of shops like to have the piston and crank on hand when they do the machining. Aftermarket parts in particular might vary a little from the published specs so a lot of guys do the machining and calculate the clearances to suit the piece in front of them.

If you havent got the necessary equipment on hand, I would get your machineshop to do the measuring - they'll have to do it anyway and crank clearances have to be accurate to within a couple of tenths. When you assemble the motor you can check the bearing clearance with plastigauge.

Do check your valve guides and look carefully at valves on the surface where they contact the seats. If they are worn or pitted you can get them refaced by your machineshop, although it may be cheaper to just buy a couple of new ones. Get the machineshop to check out the seats in the block while they have it there.

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I dropped off the block, crank, cylinder, piston, and valves. The guy was really knowledgeable. He is going to bore the block and turn the cam. He said the .010 piston should fit, the .010 under cam will not be a problem, the intake valve is good, but the exhausr valve was really worn. Going to get a new one.

Now I just have to wait for a few weeks.

So I decided to start cleaning more parts. Here is the question of the day. Can I reuse this head?

DSCF6159.jpg

DSCF6162.jpg

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Can I reuse this head?

Put a sheet of 400 grit wet and dry on a clean sheet of glass and lap the head till its flat. I use a bit of WD40 to stop it clogging.

5 minutes or so will get it nice and flat and remove a lot of those "pits".

Then take a look at your head gasket and note the "fire-ring" around the cylinder. Its the folded over metal bit that protects the inside material of the head gasket from the combustion heat. This is what actually seals your cylinder to the head. As long as the remaining pits dont cause a leak under the fire-ring, you should be good to go.

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Put a sheet of 400 grit wet and dry on a clean sheet of glass and lap the head till its flat. I use a bit of WD40 to stop it clogging.

5 minutes or so will get it nice and flat and remove a lot of those "pits".

Your a genius, I would never have thought of that :ychain:

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Sounds like its coming right along

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Keep in mind also, the K181 the lifter/tappets arent adjustable, you have to butt gring the valve stems so you may want to have the machine shop do that as long as he has everything

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looking good. I'm really interested in this build I have a K181 thats smokin and in need of some love. Would really like to go the route you are.

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