K321 bad scoring
 

I'm trying to give my 1450 an overhaul that is long past due. It's been sitting in the garage since the end of last winter when it was my snow plow and snow blower. Other projects have kept me from digging into it until now.
I pulled the engine to replace the motor mounts and swap the oil pan with a cast iron one since the oil plug had a reducing bushing in it to fix worn out threads. First worrying sign the pan had a film of silvery powder in the pan. I then noticed what looked like blowout of the head gasket so I decided to order some head gaskets and got around to cracking the head open. The bolts seemed a little too loose, so hopefully that was the reason for the small blowout. But on cleaning out all the soot and buildup I found a worrying amount of cylinder scoring. I don't have much experience with small engines so I need advice.
How bad is this? It's didn't run smoky at all since I cleaned and adjusted the carb so it was running well (as smooth as I could expect with bad motor mounts). Is it alright to put back together and use for the winters plowing without doing more damage to it?
Does it need a complete rebuild in the spring or do I just watch how it runs?

My vote is for a complete rebuild.

Here's why, looks like that piston says "010" on top so we know it's already been bored out once. You said that there was "silvery powder in the pan", that and the scoring leads me to believe that who ever rebuilt this engine didn't wash it out after having it machined.

So now you have that those fine metal particles in the bearings, in the connecting rod and crank shaft, up on your cam shaft, etc. causing premature wear.

Somehow I missed this thread when you started it Graflex.
Sorry about that. Looks to me like a rebuild for sure as noted.
The actual work of the rebuild is not that difficult and plenty of
help here on the forum.
The worst part around here is not the work I can do, but finding
a machine shop that will do it right. Or do it at all. The days of
finding people to work on small engines is dying around here.
Hopefully you can do better there.
Don't hesitate to ask. Be happy to help where I can.

Ken

Definitely seems like who ever did the rebuild for previous owner didn't know what they where doing or tried to skip some steps. I borrowed a granite surface plate at my workplace over the weekend to sand the head flat since it had some warping. I'm planning on reassembling and testing the compression in the next couple days when the head gaskets come in the mail. Really need this thing running before the snow storms hit soon.
My thoughts are as long as it has good compression and I've flush all the metal out as best as I could and I've cleaned out all the carbon buildup It shouldn't get too much worse before spring.
How should I proceed when I find a machine shop that will do a rebore? I have a lead on one that may do it. Do I bring the engine to them broken apart so they can measure the cylinder before I buy the kit of parts? I know the next bore would be 20 over but I dont know how to measure if I need an oversize crank.

Take it to the shop disassembled. All they will need is the block and the crank. I'd include the pan as well. They will tank the parts, measure the bore. mic the crank, inspect everything for cracks and advise you as to what parts are needed.

Meanwhile you will have time to clean up and paint, if need be, all the accessories, nuts, bolts, tins & frame etc. to prepare for a nice clean installation as well as address any other items such as slop in the steering, drag link, tie rods, knuckles and axle etc. and correct as needed. You will wind up with a healthy, happy machine that will serve you well for many years.

New kits come w/new valves, but I would also order new guides and have the shop install them as well. They are only an additional $10 or so. I would also replace the governor as well as the bushing for it. You will need a torque wrench and a ring compressor. Take pictures and notes while dis-assembling. Find and download a copy of the Kohler FSM, for the K-series, TP-379, and oh yes, don't forget to static time the engine while on the bench. You will be amazed as to how quick it will start when installed!

Do it right and do it once!

The last one I did was in 2019, was a K341 that I installed in a 1450.
The parts came to $215.50 and the total shop bill with a .010" bore was $231.12 w/tax.
I'd plan to spend as much if not more 5 years after.
Good luck!!

that main reason for pulling the tractor apart was a bad cork seal and collapsed motor mounts.
I have put the hydro back together after having a coworker weld on a new trunion to the hydro control and replacing the springs and the linkage swivels from the speed control.
I bolted on the improved solid rubber mounts to replacement mounting plates I had the stiffening bar welded to.
I've already shimmed the front wheel fork since it had a bit of front to back wiggle and have new steering axles I'm putting on since the right front wheel someone put sleeve bearing in the wheel and wore down the axle. I also have greaseable tie rod ends to swap on.
I should be able to finish rehabbing the rest of the tractor and getting the engine back in service for now in the next week and a half.
I'm not really interested in repainting the whole thing. I'm power washing all the body parts as they come off and am rubbing boiled linseed oil into the rusty spots to seal the rust from getting any worse. I like that amount of wear it shows for being 50 years old and being repainted once before.

Yeah, i tried those solid rubber mounts, a guy sent me a set free, wanted me to try them.....
Installed them and drove around a bit.....
Yanked them back out and installed new proper ones and never looked back.
Smooth as silk now and one of the quietest Cubs in my stable.

To fully answer your question:
All have given you good advice which I agree with first and foremost.
Yes you can run it as it is, if it was not knocking or smoking badly which you say it was not..
Also, winter snow plowing with a blade is usually not at full governed rpm's and during cooler weather which is helpful.
I've seen worse, panting and pissing oil out the breather and fouling
the plug.
Also, your other repairs hopefully will turn out to be successful, but in the event something is not right, it will be addressed when you have time to do the re repair when the engine is out for your overhaul.
If you button it up the way it is, do be advised to retorque the cylinder head after a couple of heat cycles. which is not mentioned in the service manual.

You can do a search on here, as it has been covered multiple times.
If this 2nd retorquing is not preformed, it will blow the head gasket again, just a matter of time, and you experienced that as you said the head bolts were not as tight as they should be.

I have to look at all the shrouding to see how easy it is to pull the top part off. Seems a bit difficult with these fully shrouded engines.
The main problem with the head was a very visible warp when placed back on the engine, but thanks for the experienced tip.
When I bought my model 70 the owner said he retorqued to head bolts the previous year and I did the same when I went over it and fixed up up some things. I guess Kohler's just have that as a maintenance thing you need to check periodically?

While it's apart, you can bore a hole in the shroud right above the bolt heads for a socket to go thru.
I don't know that it causes any great cooling issues but if it bothers you plug the holes with these....