1969 Cub Cadet Model 105 Hydrostatic Drive Garden Tractor - Part 1

I purchased this 1969 Cub Cadet garden tractor in 2011 from a good friend who had purchased it used in 1972. They put it to good use up until the time I got it. It was garage-kept throughout their ownership, so it was in fairly good overall condition, including original paint on the hood and most of the body/frame. The seat also looks like it is original to the tractor. A rear-mounted Model 1 rototiller came with the package. The seller was in her late 60's when she finally decided to part with her baby.

This tractor has a 10 horsepower Kohler K241 single cylinder engine. The previous owners had engine work done at some point in the past but I don't know what was done. I did notice the engine block was not painted yellow, so I think it was a replacement.

The Model 105 came standard with hydrostatic drive, which gave an infinitely variable ground speed from creeping to full speed. This tractor also has the optional hydraulic lift system (seen in the above photo to the rear of the starter/generator), which was an upgrade over the standard manual lift lever. Below is a photo of the dash, showing the chrome hydrostatic drive lever in the lower center of the picture:

One major issue the tractor had when I bought it was a loud rod knock, which was the main reason I parked the tractor and never used it after I bought it. I decided a couple days ago to finally delve into the engine problem. I'm hoping it's just a worn out connecting rod.

The hood and front grill are off, as is the starter/generator unit.

Here is the engine out of the tractor.

Engine teardown begins.

The piston looks pretty good, and the cylinder didn't have a ridge at the top, so it is in decent shape. The connecting rod big end hole measured 1.501, which is within specification. Hmm, that means the crankshaft is probably worn.

Yep, the crankshaft journal measures between 1.488 and 1.493. The maximum wear limit is 1.4990, so my crank is .011" too small. Bummer.

I have a couple of options. I could have the crankshaft reground .020" undersize and buy an undersize connecting rod, or try to find a used crankshaft with a standard size journal, since my connecting rod is still within specs. The second option would probably be cheaper but the problem is finding a crank that isn't worn and that fits this tractor configuration.

With the crankshaft being so worn and the connecting rod not worn at all, I'm thinking that whoever rebuilt the motor got a new block and connecting rod but did not check the crankshaft journal dimensions. One thing I haven't done yet is to mic the cylinder bore and piston. The piston does look a little worse for wear, as it had dings in the top surface, like something had gotten sucked into the bore and rattled around some, so it may still be original to the tractor. Maybe whatever got into the bore and rattled around had ruined the original block.

Stay tuned.