Advice needed for first Kohler engine rebuild

[tntatro 171]

Hello, I have a k241 that I bought a while back and would like to start on it some time this month. It has a cracked piston and the guy I got it off said it needs to be re-bored. By using my dial calipers at the top of the bore it appears to be a standard bore.

 

I downloaded the service manual so I can probably handle taking it apart. Do I just start disassembling it step by step by the book? and what tools will I need for checking specifications that will be sufficient? I have feeler gauges and dial calipers but nothing for inside the bore.

 

It seemed like a good deal for $40. It is nearly complete except the muffler, I also have parts in a box such as shrouds, pulley, cylinder head, coil and a couple carburetors with air filter housings.

[953 nut 55,198]

Your best bet is to take the engine apart and take the block and crankshaft to an engine machine shop. They will let you know what may need to be done. Without the proper precision measuring equipment and the skill to use them properly you could waste money on parts that won't give you satisfactory performance.

[The Tuul Crib 7,336]

1 minute ago, 953 nut said:

Your best bet is to take the engine apart and take the block and crankshaft to an engine machine shop. They will let you know what may need to be done. Without the proper precision measuring equipment and the skill to use them properly you could waste money on parts that won't give you satisfactory performance.

[Shynon 7,459]

5 minutes ago, 953 nut said:

Your best bet is to take the engine apart and take the block and crankshaft to an engine machine shop. They will let you know what may need to be done. Without the proper precision measuring equipment and the skill to use them properly you could waste money on parts that won't give you satisfactory performance.

[oliver2-44 9,743]

That looks like a GREAT deal for $40.  The spare electric starter is worth that!.  To get a good bore measurement you need to be down past where the rings would be with the piston at the top of the stroke. When your measuring at the very top with the dial caliper your in an area that gets no wear.  Below is a great threat that is pinned in the "Instructional Threads Section"  Your engine is a little larger, but the process is basically the same. 

 

I'm also about to start my first overhaul in many years. Here's some good responses I just got about governor and Camshaft parts.  Also a few machine shop addresses in case you can't find one near you.  Post a thread on your rebuild.  Lots of good help here, and you will also be helping people like me that, also are on the learning curve. 

 

[Metal225 29]

i found thease vids on you tube that im going to use this summer when it warms up ,there is a few of the just follow the seires

 

 

[The Tuul Crib 7,336]

 Norman is a great guy and I have watched a lot of his videos. Very informative. Thing I like about him is when you call usually he answers the phone! 

[Dan693 510]

I recently had a Kohler K twin bored to 30 over, block cleaned, and 2 broken bolts removed for $250 so a single cylinder should be around a buck fifty.

Add a oversized piston and rings, gasket set, and misc. and you'll end up with about 3 bills in the engine.

 

Work a little OT and your good.

[Sarge 3,463]

If that thing got hot enough to crack a piston - spend some time cleaning the cooling fins very thoroughly and check for cracks in the top two fins/top of block. Those engines don't generally crack a piston without being seriously overheated. I have a 341 here that no one ever cleaned the flywheel screen and fins - packed it full of grass and dirt and now the block is junk, being cracked clear across the top to the exhaust valve. Cast iron can take a lot but still has its limits.

 

Sarge

[tntatro 171]

Thanks for all the responses. I may start to take it apart tomorrow. I'll clean the fins around the exhaust and check for cracks first.

[953 nut 55,198]

2 hours ago, tntatro said:

I'll clean the fins around the exhaust and check for cracks first

It would be a good idea to have the cylinder Magnafluxed. If there are cracks they may not be visible but will show up with magnaflux.

 

 

[ebinmaine 67,455]

@953 nut

good idea and thank you for sharing that video. I've heard that term a million times and never knew exactly what it meant.

[artfull dodger 394]

Do NOT forget to check and set the camshaft end play!  This little step that is mostly forgotten by many that rebuild these(even professionals) And this is the cause for the notorious "kohler knock" that so many are plagued with in the mid rpm area.  Sounds like a rod knock but its the camshaft slapping back and forth due to excessive end play.  The procedure is covered in the rebuild manual for the K series engines.    Mike the Aspie

Edited February 14, 2019 by artfull dodger

[tntatro 171]

I took it apart a little today and so far have not seen any cracks. I have ordered some spray type dye I found online for finding cracks so I'll try that next week. There is a deep scratch near the intake valve and the exhaust valve seat has some damage to the surface.

 

I mainly just looked at the top around the valves and piston for cracks, are there other common areas that are prone to crack that I need to inspect?

[Sarge 3,463]

Mostly just around the top fin/top of the block. Might want to clean and inspect the rest of it if it has ever been previously rebuilt - some toss their rods and put stress cracks in the lower half of the block.

 

Sarge

[tntatro 171]

Today I took the engine apart except the bearings. I was a little confused when I got to the part about the balance gears, apparently this one doesn't have any. Other than the piston I don't see any obvious signs of cracks. I still have to clean it up more and take a closer look. I've sprayed the block down with engine cleaner several times and wiped it down and it seems like I may have to empty a whole can on it. The exhaust valve has some pitting or damage to the face.

 

I bought a micrometer set and bore gauge so I can check specifications. It seems like I'll be spending a lot more time cleaning before I can check anything.

[ebinmaine 67,455]

5 hours ago, tntatro said:

seems like I may have to empty a whole can on it

No worries there.

I've used 2 or 3 cans and still not been quite satisfied.

 

Just keep at it.....

[Sarge 3,463]

A decent sized metal tub - like an old turkey roaster pan is perfect for cleaning small engines up. A couple of gallons of diesel fuel, a few nylon and metal scrub brushes and it will look new in short order. Diesel fuel will dissolve all the old gunk in short order without the noxious fumes associated with brake cleaners. Years ago, a can of brake cleaner would take off the gunk and any paint along with it in one pass - the stuff they sell us today is a lot less potent and watered down due to skin/environment hazards. The diesel fuel will also lessen the risk of damage to good, solid enamel paints that are old and fully cured. The oils in the fuel will also protect the metal parts for a short time until the machine work is performed - just wipe it down really well.

Sarge

[tntatro 171]

I got the bearings out and cleaned the block up a bit more. It could still benefit from a diesel bath but I could not find a good tub for it. I do have plastic totes of various sizes.

 

I sanded the bore a little to clean it up and it has a ring cut in it. I assume it is where the bottom ring reaches its lowest point or maybe damage from when the piston broke. 

 

I also tried using the dye and developer stuff on the top of the block and still no signs of cracks. I'll try again because I'm not sure I did a good job with it. I think the block is good though as far as not having cracks.

 

Tomorrow I'll try to find a good size tub and get some diesel to clean things up a little better and start cleaning parts to check the specifications.

[953 nut 55,198]

Looks like your cylinder may be a bit egg shaped, not unusual. Be sure to double check all of your measurements, it is a bit tricky doing bore gauge evaluations. 

[WHX?? 48,815]

Sounds like the guys have you covered so just chiming in to follow and show you this. From a 241 that I ain't gonna fly at 33,000 ft but did end up working  the snot out of...very hard field plowing.  I knew this going into the build but don't have alot of money tied up into the rebuild of the motor so just figured to roll the dice and see what shakes. Things miced up fairly well so a re-ring and that was it. Your situation might be different but just sayin...this motor is my best 10 HP by far. Guys told me I'm on crack for doing this but two years later they are still wrong. No head issues and nothing but pure 241 power.

[WHX?? 48,815]

I take that back I did have some head issues. ... for not retorqueing head bolts like I was told to do  after run in. 

[Howie 886]

Exhaust valve is toast, will probably be to thin on the edge after being ground. That ring at the bottom is 

probably because it was run with the skirt broken on the piston, rocking in the cylinder, Not normal wear

to me. Valve seats will probably clean up ok.

Edited February 22, 2019 by Howie
error

[Sarge 3,463]

The crack in that block is identical to the one in my 341 - except mine clearly goes all the way into the exhaust valve seat. When I got that C-160, the first job was to clean out the gunk from the engine tins and the cooling fins - both were plugged badly. I didn't find the crack until the first really cold winter day when I started it and noticed exhaust puffs coming from the cylinder head gasket area - I figured the gasket was blown but ran perfectly otherwise. Later, removed the cylinder head and found that crack. It would run fine, but when it was really cold it would leak, then seal up once the engine got to full operating temperature. The connecting rod finally bit the dust and the thing is knocking badly - I don't feel like that one is worth messing with other than scavenging parts from it, the block is toast. Really a shame, though - that is one of the strongest 341 stock engines I've ever had to date.

 

Sarge

[tntatro 171]

I cleaned the block up in a plastic tub today. I used kerosene instead of diesel because I had a gallon already. It seemed to do fine.

 

For the bore measurements I got:

- 3.2655" for the overall largest measurement.

- .0035" for the taper

- .007" for out of round.

 

For the crankshaft I got:

Middle for big end - 1.4802"

Flywheel side - 1.5742"

PTO side - 1.5742"

 

Tomorrow I'll ask around about a good machine shop in the area. I used a dial bore gauge and micrometer for the bore. Not sure my measurements are accurate but the specs I got are pretty far out. From what I read on forums this block can be bored up to .030" over for a 12 horse piston. Not sure if that is true or not but if it is then maybe this block has a bit of life left to it.