K241 rebuild help needed

Pswan · #1 02-08-2014, 06:18 PM

Hello all. I was given a 100 from a co-worker who had no idea the history of the tractor other than it threw a rod while trying to pull a trailer out of the mud. I have the machine apart replacing almost everything because it was left in the weeds for a couple of years and most things are rusted together. At any rate, one of my true loves is to rebuild engines so I was excited to get into the k241. This is my first cub cadet but figured the internals of the engine would be familiar. It was except for the method of removing the cam, haven't seen one that rides on a shaft like this. The block skirt isn't broken and the cam itself looks good, the piston is marked STD. I like to measure everything before going to the machine shop so measured the piston bore and crank journal in 6 places, 90 degrees from each other in triplicate. To cut to the chase, the largest bore is 3.2785, limit for std is 3.254. This appears to be 0.026 inch over std, is this possible for a std bore piston? At least one that "ran fine" until the rod broke? Also, the crank rod journal was found to be 1.4800 at the smallest. Std is 1.5000. This looks to be 0.020 inch under. Smallest rods 0.020 inch under? How did this not have a huge rod knock. Maybe it did and he didn't notice. Seems odd. Is the crank wasted? Anyone with some insight? Long winded but appreciate any input. Thank you.
Pete

Sam Mac · #2 02-08-2014, 07:04 PM

Pete

It is so refreshing to have someone that knows what he is talking about. I'm sure the guys that know these engines much better than I do will chime in and work with you. Dvogtvpe, Merk and J-Mech have forgotten more about the older Kohler’s than I ever knew. I’m sure that they can help you.

Merk · #3 02-08-2014, 08:19 PM

Pete,

What measuring tool(s) did you use? Was it a mike-bore gage?

What parts were ruined?

Standard bore is 3.251. There was 4 different pistons for your K-241. They are STD-.010-.020-.030. They are mark with the numbers/letters I listed earlier.

You stated the bore was 3.2785. The biggest bore you can have is 3.281 (3.251 + .030). That leaves .0025 before bore is too big.
Your options are
1. You can try to have an automotive machine shop bore it
2. Different block
3. Install a sleeve in the block
4. I know some have bored and installed a piston from the next size bigger engine. I wouldn't do theat because it makes ther cylinder walls to thin.

If it was my block I would not do the first choice because there is barely enough materal to bore.....too easy to go oversize. The last block I had a sleeve installed cost around $90. I have three K321s that are sleeve with no problems. Rebuildable blocks can go for $25 to $75. I would find a different block if it came into my shop.

Depending on how the crank journal looks you may be able to reuse it as it is providing modifing a Kohler rod so it fits a .020 rod. The rod will need a bearing installed. Kohler rods are the only rods that can be fitted with and undersize rod bearing. You can weld the crank journal and have it machine to factory size. That will cost big dollars.

The measurements and last rebuild scare me. The previous builder didn't not know what they were doing. You would be better off with a different block and crank assembly. You could go with a K241 or K301 short block and reuse the carb, cylinder head and starter from your K241.

Let me know if you need some help....sounds like a fun project.

sawdustdad · #4 02-09-2014, 02:08 AM

If the piston is marked STD, and the engine was running prior to throwing the rod, I suspect your measurements are off somehow. They don't make sense. Suggest you take it to a local machine shop and let them measure it as a double check. If your measurements are correct, the other advice from Merk is good.

Pswan · #5 02-09-2014, 11:33 AM

I can't put my finger on it but while disassembling the engine something seemed "fishy". I figured if it hadn't been opened up all panels would be tough to separate but some came off easy. Like I said, rebuilding engines is fun for me, big and small engines so I had a feeling how this rebuild should go but it just never seemed right. I suspect someone has been in the engine who didn't know what they were doing. The top and bottom of the cylinder measures 2.2500, standard, but there isn't a sharp ridge at the top of the cylinder. I wonder if someone put in oversize rings on the original piston. Still doesn't make sense. I'll take the advice and remeasure everything. The block by the way is stamped k301 so I suspect I can go 0.030 over. I don't want to pay the machinist to measure to only find I posses junk parts. I'm measuring with a bore gauge and digital caliper. As a side note, I'll have to figure out how to post pictures, you'll get a kick out of the carbon stalactite blocking flow in the head. A true testament to the will of a flat head to continue running at all costs. If I didn't trust the guy who gave me the tractor I would be convinced the engine was put together with mismatched parts so the tractor "includes and engine" to sweeten the deal. Thanks for all the a advice.
Pete

dvogtvpe · #6 02-09-2014, 12:37 PM

I'd think if that piston was as loose as you say it would have hammered pretty bad and broken the skirt. but anything's possible

Pswan · #7 02-09-2014, 02:20 PM

Sorry Merk, I keep misquoting standard bore size. 2.251. Thank you.
Pete

J-Mech · #8 02-09-2014, 02:42 PM

It's possible that it was worn that bad and still running. I just tore down a K301 and it had a standard piston. It had to be bored .030" to be true again.

I'd just take it to a machine shop. They'll tell you what you need.

sawdustdad · #9 02-09-2014, 07:39 PM

Quote:

Originally Posted by Pswan

Hello all. I was given a 100 from a co-worker ...so I was excited to get into the k241. .... the largest bore is 3.2785, limit for std is 3.254.

large bore for a STD piston in a K241

Quote:

Originally Posted by Pswan

The top and bottom of the cylinder measures 2.2500, standard, ....The block by the way is stamped k301

A K301 can't measure 2.250.

I'm really confused...

Pswan · #10 02-09-2014, 07:49 PM

The pto side of the block has k301 embossed there. It appears to be one of the k241 engines that is based on a k301 block. My understanding is that kohler didn't have enough k241 blocks for the run and had to use k301 blocks with a k241 bore. If true, the advantage is a thicker cylinder wall..
Pete