Kohler small block rebuild tutorial

[prondzy 3,881]

     I thought I would try to make a step by step teardown, measurement and rebuild of a k161 the way I do it. I see a lot of people wondering if they can do it,and I thought this might help.  I do use the kohler manual as it does give step by step instructions also. 

    The only "special" tools I use for teardown and measurement are a set of telescoping gages, a dial or digital caliper that reads to .001"  (I prefer digital it takes out some guess work), a valve spring compressor and a harmonic balancer puller (for the flywheel) all four of these items I use can be bought online or from HF and are relatively cheap and can be used for other projects. 

Tools needed for assembly are a ring compressor, shim gages, a valve lapping tool with compound, and a torque wrench (none of these tools have to be top of the line, I use a $30 in/lb torque wrench for the connecting rod and a $50 ft/lb  torque wrench for the head gasket bolts. ( the last two can usually be borrowed from a friend  if you don't have them.

Edited February 8, 2016 by prondzy

[prondzy 3,881]

 

So here is the Kohler k161 motor from my 702. I believe it to be the original motor but I have no idea if it isn't. Truth be told I have never been worried about spec numbers, they have never made a difference to me a kohler is a kohler and ill make it run. The motor when I got it was missing the air cleaner assembly and I could not get a full rotation out of the crankshaft . I thought there was a stuck intake valve and I think I was right because I poured a little kroil penetrating oil down the carburetor a few weeks ago and this morning I turned it a full revolution no problems..

The first thing I do is take a few pictures of the overall engine and especially trotted cable linkages, and locations of hole used for the govenor ( note the govenor arm uses the lowest hole and the carb uses the farthest out hole)

Edited February 8, 2016 by prondzy

[prondzy 3,881]

First remove all the tins along with the starter generator and the muffler.  I didn't remove the muffler before hand  so I'll have to remove it at work by clamping the block in a hydraulic press. It is easier to remove the muffler while the motor is bolted to the tractor using a little heat and a pipe wrench. Once the tins are gone remove the head and find out what your dealing with. A lot of black carbon buildup can be normal for these old girls.

I take a gasket scraper and clean the top of the piston an then use a brake cleaner and a brush to look for any stampings in the head

This one is marked STD for standard bore this is a good sign. Note the divets in the top of the piston something has been through this engine a rock or nut, something hard.

Edited February 8, 2016 by prondzy

[slammer302 2,155]

was the spark plug hole stripped out? I see what looks like metal shavings we're the plug hole would of been.

[prondzy 3,881]

Use the harmonic balancer puller to remove the flywheel. 

Next we need to remove the valves, thake, off the breather cover (note the drain hole that goes to the bottom, if this is toward the top the breather will film up with oil and puke out the breather.

I use a valve spring compressor and a magnet, these can be bought anywhere once again not very expensive.

Once the keepers are removed, release the spring compressor pull the valve out the top and pry the spring out with a flat head screwdriver.

The intake valve (bigger one) I thought had a chip out of it, you can see in the picture. I thought this was from the marks in the top of the piston, the chip was just carbon that broke off, I verified this by cleaning up the valve head on the wire wheel.

The end of the valve seems a bit rough I might take a chance on them for cleanup but I will probably replace. Most valves are reusable, unless they are bent, burnt, or pitted. When you take the block to th machine shop take the valves with and have them and the seats reground, if you are spending th money on a rebuild do it right. Why spend money to have the cylinder bored and then just lap the valves to have compression loss. The machine shop i use charges around $10 a valve to regrind them, trust me it's worth it.

Edited February 8, 2016 by prondzy

[prondzy 3,881]

Time to get at those internals so next remove the oil pan, hopefully you drained it before you started. This is where this little home made engine stand comes In handy, but you can roll the block over on the table. 

Remove the four bolts that hold on the bearing plate and remove the plate if you cannot rock it off by hand a gentle tap from a deadblow can help.

This connecting rod has the bendable nut retainers use a cold chisel and a ball peen to tap them back slightly to get a socket on the rod nuts.

I rotate the piston to the top (head end) of the block and unbolt the rod cap this way I can rotate the connecting rod 180° and tap it out of the block with a deadblow hammer. 

Set the crank aside on a safe place so it doesn't roll off a table onto the floor. Look for the camshaft pin on the pto side of the block. Use a long punch to hammer out toward the bearing plate side. When the camshaft come out there will be a small shim washer on the pto side of th cam that you need to hold onto. I like to use a little mechanics wire and wire the shim to the end it came from so I remember in a week or two when I reassemble that's where it goes.

 

I then pull out the tapets, I mark them with a paint pen or sharpie because they have "mated" with each cam lobe. I usually put each valve with its keepers, tapped  and springs in a bag marked intake or exh.

Now the govenor gear needs to come out remove the brass govenor retaining nut found here

Before removing take a picture or at least note the orientation of the throttle cable holder and clock potion of th round disc. Best to take a picture. O ce you have removes the brass nut you will find a screw head hidden behind the disc. Remove the screw it retains the govenor gear inside the block from falling off its shaft.

Take out the govenor gear from the shaft ( you can see at the bottom of the block.) CAUTION there is another shim washer between the block and the govenor gear on this shaft don't lose it. Use mechanics wire to tie it to the gear until reassembly.

Reach inside the block an take out the govenor shaft that stuck out of the brass nut, it will remove from the inside. 

[prondzy 3,881]

Now I remove the old piston rings, if they break no big deal you don't need them any way. I make six measurement to figure out cylinder taper and out of round. I write them on a sheet of paper which I will post t a pic of. I measure what I call the thrust measurement ( the thrust direction of the piston) and the pin measurement ( runs parallel to the piston pin when bolted to the crank) I use the piston as a support for the telescoping gage to help in the accuracy of the measurement this can take some time and patients to get the hang of, you can leave a single ring on the piston for tension to hold it in place while doing this. I measure top, middle and bottom of the bore on both the thrust and pin sides of the bore. Use the t-gage to measure the bore and the caliper to measure the t-gage.

 I take one measurement at a time and write it down the move to the next measurement, sheet then looks like this

 With it written down I can figure taper and out of round. There should be little to no wear on the pin side so count on those three numbers being the same or darn close. The thrust side is where the cylinder wear is. Taper just subtract the lowest thrust number from the highset thrust number and in my case it's .006"  for out of round you take the greatest difference between thrust and pin but they must be from the same level measurements, i.e the top thrust and the top pin not the top thrust and the middle pin.

My max taper is .006" and the out of round is .006" 

Now comparing my measurements to the kohler manual

You can see that I exceed th max out of round by .003" which is where most people think they can re ring and hone and keep going... not a good idea, you would be putting a circle in an oval good luck trying to keep it from burning oil.

If you are following the picture real close you will see my measurements are smaller than the standard bore for a k161 this is because I have a k161 with a small bore, the small bore k161 is no longer available and i will need to go to a standard 8 hp piston, being tue same as a large bore k161. But if I were building say a k181 with the numbers I have and the condition of the cylinder walls I could bore it out to .010" and not have any issues but I like to air on the side of caution and would go to a +.020" piston because at .010 I would have .004" to clean up the cylinder walls (any scratches I don't see right now) it would only remove. 002" from each side of the wall.

I also measured the crankshaft with the caliper in 2 spots

Nevermind the numbers the pics are just for show. My actual numbers showed a .001" out of round nothing I'm concerned with and the connecting rod showd no signs of wear or scoring so it looks like a standard 8hp piston and a standard connecting rod  kit with valves needs to be ordered, will try to get ordered in the next week or two to complete this thread. I will be using an aftermarket stens/rotary kit from ebay, I have used many of these kits never had an issue with quality and most builds have been in workers.

Don't forget to remove your other crankshaft bearing and seal still in the block a brass drift and a hammer will work don't want to send these to the machine shop.

 

Edited February 8, 2016 by prondzy

[WNYPCRepair 1,921]

1 hour ago, prondzy said:

I could bore it out to .010" and not have any issues but I like to air on the side of caution and would go to a +.020" piston because at .010 I would have .004" to clean up the cylinder walls (any scratches I don't see right now) it would only remove. 002" from each side of the wall.

 

 

I was about to ask you to clarify this, but I think I figured it out. 

I think you are saying if you bore it out to .010, it will only take .002 (.004 total) from the sides (thrust) that were out of round to start with, because they were already .006 larger (wider?) than the pin measurements? so if scratches on the pin side were deeper than .002, they would bot be bored out?

Also, are there any rod bearings? I always remember my dad tapping in bearings on car engines. Or was that just on the crank?

 

 

Great post, by the way. Thank you. I might get up the courage to try it after this. 

Edited February 8, 2016 by WNYPCRepair

[prondzy 3,881]

6 hours ago, WNYPCRepair said:

 

I think you are saying if you bore it out to .010, it will only take .002 (.004 total) from the sides (thrust) that were out of round to start with, because they were already .006 larger (wider?) than the pin measurements? so if scratches on the pin side were deeper than .002, they would bot be bored out?

Also, are there any rod bearings? I always remember my dad tapping in bearings on car engines. 

Yes you have the idea right the scratches might not be removed.

 

There are no rod bearings, although you can machine them into the rods, just about all the kohlers are standard or .010" undersize. 

[prondzy 3,881]

9 hours ago, slammer302 said:

was the spark plug hole stripped out? I see what looks like metal shavings we're the plug hole would of been.

Slammer, it is possible there was a different looking autolite spark plug in the hole, I think it's just rust from the aluminum head, the park plug was loose in the hole I suppose vibration from moving it around knocked ir it the head.

[pacer 3,174]

FANTASTIC post!! Deserves more than a simple "like this'

 

Thank you for taking the time, posting something like this can take a lot of time - and skill...

[pfrederi 17,863]

Great Job and goo info especially on the measuring!!!   Thank You

[wrightorchid 261]

This is very helpful.  I may have to rebuild my Kohler Magnum 12 some day.

[squonk 41,309]

Just a thought. When removing the bearing plate I would measure the old gasket thickness. It will give you a "starting point" when reassembling the crank and checking the  end play.  Great post and Pics! 

[buckrancher 2,694]

don't trust dial and or digital calipers for less than .002  your ahead of others in what you are doing but you need to buy some good micrometers for accurate measurements

good pics and write up keep it coming

 

Brian

[prondzy 3,881]

2 hours ago, squonk said:

Just a thought. When removing the bearing plate I would measure the old gasket thickness. It will give you a "starting point" when reassembling the crank and checking the  end play.  Great post and Pics! 

Squonk this is a good idea, I have found in the other engines I have built that it can be hard to pre-measure the new gaskets because you have to compress them to read the crankshaft endplay. Well noted though I will give it a shot with the old gaskets still laying around.

 

1 hour ago, buckrancher said:

don't trust dial and or digital calipers for less than .002  your ahead of others in what you are doing but you need to buy some good micrometers for accurate measurements

good pics and write up keep it coming

 

Brian

Yes good point buckrancher I would prefer to use higher quality measuring tools, i work as a mechanic and understand the importance of quality and accuracy. I guess I'm trying to show that it can be done with cheaper tools,  and you dont need to spend $100 + on a dial caliper and micrometers for a one time deal, which puts you in the game better than a hone and re ring which doesn't work. I have been using these tools to build all my kohlers and have built many kohler engines that are working great.

[Horse46 519]

When I did my K341 I had to push the piston out past the rings to rotate the crank back around, the con rod appeared to long to clear, maybe I did something wrong?

 

Cool thread, as I did mine for the first time as a non mechanic I could have used something like this, maybe a bit more detail of what to expect problem wise, like when removing the flywheel, or the valves?

Another area I struggled with was refitting the crank and then the side plate, ref the end play, that was for a non mechanic quite confusing.

Keep it coming though its invaluable for peeps like me.

 

[prondzy 3,881]

I just ordered the rebuild kit yesterday morning looks like I should have the parts early next week then off to the machine shop, hopefully will be reassembling in 2 weeks but in my spare time I will post a few little things I like to do in the meantime to be ready for assembly. Keep checking in 

[buckrancher 2,694]

1 hour ago, Horse46 said:

 

Another area I struggled with was refitting the crank and then the side plate, ref the end play, that was for a non mechanic quite confusing.

 

 

if you are not changing the end plate or crankshaft you would use the same thickness gasket and shims (if there are any) on the end plate new bearings will not change end play

 

Brian

[Horse46 519]

Thats cool, bearing were the same, as is the crank n side plate, I still haven't fired her yet, I'm a little scared!

[953 nut 55,743]

On 2/12/2016 at 2:55 PM, Horse46 said:

I still haven't fired her yet, I'm a little scared

Nothing to be scared of, I get a warm feeling every time I drive a  or my street rod knowing that I held every component of that reliable engine in my hands.        Of course if you are still scared make sure there are no witnesses, if no one saw it; it didn't happen!  

[prondzy 3,881]

Still waiting on the rebuild kit to send it off to the machine shop hopefully i can do this this week. Didnt get mich done today just working on the little things. I rebuilt the starter generator (no pics) and I cleaned the head.

Here it is all dirty and carboned up, note the spider cob webs between the fins these will definitely slow down the cooling.

After scraping most of the carbon 0ut I used a small wire wheel in the drillto clean up all the old carbon. If you don't have a wheel like this a small wire brush and some carb cleaner will work just fine.

I blasted the head to clean it up, note the broken fins, I don't think the missing chunks will cause any problems so in going to use it. When I blasted the head I tried to avoid the combustion chamber area. We use and aggressive blasting media and the pitting inside the chamber would cause carbon deposits to stick.

Next is to surface sand the head,I have read some people using a peice of glass for a smooth surface, I have a 12x12 granite tile you can pic these up at any home improvement store, a sheet of 600 grit wet dry sandpaper,  and some glass cleaner. Wet the paper and the head with the cleaner and move the head in a circular or figure 8 pattern with a light to moderate pressure.

After a minute of sanding I wiped off the head to reveal the high and low spots. A plus to not blasting this surface the the dirt/carbon shows the low spots. Note the high areas are starting to shine.

After a few minutes of sanding I think this head is true flat again note the dark low spots are gone. I beleive when you build these motors every little detail counts. This is a little detail but it could be the difference in an okay sealing head gasket and a perfect seal.

Here it is ready for install. I plan to rebuild the fuel pump and carburetor because this one will be a worker. Just curious if anyone wants to see those teardowns in this thread or leave them out. Please input.

[elcamino/wheelhorse 9,351]

I would like to see the fuel pump and carb tear down and re build.

[WNYPCRepair 1,921]

34 minutes ago, elcamino/wheelhorse said:

I would like to see the fuel pump and carb tear down and re build.

 

 

Definitely.

 

And why glass cleaner, and not just water?

[prondzy 3,881]

11 minutes ago, WNYPCRepair said:

 

 

And why glass cleaner, and not just water?

You could use water, I would use a soap/water solution for lubrication. But the convenience of the glass cleaner already being in a spray bottle is the biggest reason.