+1 what Terry said. The end play is set by the distance between the main bearing thrust surfaces, at least one of which is known to be worn. The flywheel side main bearing is probably just a needle bearing or maybe even a bushing, with the case acting as the thrust bearing. I would machine the case, and put in a home made thrust bearing. Bronze or steel would work, maybe backed up with hard steel shims. Or you could buy an actual thrust bearing and machine the case to fit. Something like this: http://www.vxb.com/page/bearings/PROD/Kit8676 I'm guessing somewhere between 5 and 10 thousandths would be about right for the end play when everything is bolted up.
I would finish the teardown, and see what it looks like on the other end. To get the flywheel off, take the nut off, and then pop it with a hammer in about 3 places on the top, not on the side, careful not to break the fins. Don't beat on the threaded end, it will mushroom. Normally they pop right off.
Chances are theres no "bearings" in it at all. Just a thin bronze, brass type deal that the crank rides on. I have a 24hp kawi tore down here now off one of my mowers. Same idea. Thats a 2-4000hr motor in tough comercial conditions so I dont think it had 250hrs on it. It should most likely have a low oil cut off on it to prevent it from running dry on a hill. I dont think you got the whole story, or something did not work right on it. At any rate well worth the repair. Get the case and throw it together. Once the cover is on the crank play will be all but gone.
Check the oil pump. I have one of those that lost oil pressure. The gear inside the pump spun on the shaft. This one has on oil pressure shut down switch so there was no engine damage. If there is no such switch on yours that may be the problem.
I would not machine the case cover as JimDawson recommends I would replace it. It is the main bearing and you have already demonstrated there was metal transfer,a new cover will provide a new thrust face and a new bearing surface.
I did a kawasaki 620 engine that did about the same thing as your kohler. It was built just like that the parts even look very much the same.
It had a sleeve bearing on the flywheel side and the pto side had the crank just running in the aluminum. It seized the crank to the case from low oil use. I polished the crank up on the lathe with 600 & 800 sand paper. I bought two of the bearings for the flywheel side...installed one in each side. Machining the pto cover out to accept the sleeve type bearing.
Replacing just the cover was not an option on the kawasaki as the block assembly was sold as matched set. Not sure but the kohler is likely the same way.
I am going to assume that this is a vertical shaft engine. If it is, then the side loading from a belt can wear the bearing surface out of round.
If you have a end play problem, then you have a lubrication problem. Most likely, oil not being changed when needed.
Check the side cover for excessive wear. There is going to be some wear from general use.
There are clearance grooves, around the crank bearing area, to allow lubrication to the the bearing surfaces. With the side cover tight on the block, measure the end play.
These engines will tolerate quite a bit of end play.
If the thrust area is excessively wore, then this area can be welded and filed, milled to take up excessive play.
If the upper or lower bearing bore is wore excessively, they can be bored and a teflon coated sleeve bearing can be installed.
This is how I repair engines for the lawn mower racers and tractor pullers.
I should have look at the vid, your engine is a horizontal shaft and was ran low on oil.
Check the oiling circut for aluminum fineings.
The side cover is repairable as mentioned.
You can use muriatic acid to clean the aluminum from the crank. Warning! do this outside, have plenty of water to rinse with and you may want to use rubber gloves.
Don't do this on your concrete it will eat it, get the idea?
I would change the rings, with the hours on the engine. Check the outside of the cylinders for grass and oil accumulation. A common problem with mower engines.
Thanks for all the replys, you guys got me really thinking on how to proceed with this build. Here is what I'm dealing with
1. Got engine for free
2. Broke for the next few months
3. Got a mill and lathe (I'm a beginner)
4. I have nothing to put the motor in yet.
5. Have plenty of time, I'm retired.
6. i got a powder coating gun and access to an oven the size of a former east block Russian car ( I got to visit east Germany before the wall came down)
7. I was able to download a repair manual from kohler( thanks to whoever suggested that.(john deere makes you buy them)
8. I got anwirefeed welder that I've never used.
I can just inspect and replace what's needed to get it running or I could do a complete tear down or do something wild and do like someone suggested and refurb the parts I got. That would give me experience using mill and lathe.
One other point to consider before deciding to refurbish the existing end cover is that you don't know the dimension for the internals of that cover. In other words, if you had a plan in place to repair that cover, to what dimensions would you make the thrust bearing portion of the cover? That information will not be readily available anywhere, yet those dimensions will be critical. I hate to say it, but your best bet might be to get the used cover off of eBay if you can afford to go that route and if that cover is in decent shape.
One point to consider if you do decide to make a thrust washer to take up the excess end play created by the impromptu "Machining" of the inner case. Mill it off even and square and slip it back into position and measure the total amount of distance the shaft will move and make a sintered bronze or oilite bushing that will fill that gap less about .008 to .012 and call it good. Welding that will never work because you will never ever get the metal to give up all the oil that has soaked into it over time resulting in a poor quality weld with an overheated casting. We used to repair them like that all the time on Scag Commercial mowers down here in the south and the repair usually lasts longer than the rest of the engine. We tried baking the casting, soaking, pressure washing and any other of a myriad of ways to clean that surface and we could never get a good clean surface to weld on to create a build up. The bushing is very similar to the thrust bushings that they install at the factory only considerably thicker to make up for the lost material from the" machining" and subsequent milling to square off the damage.