What exactly is the "Kohler rattle"?
 

So this 102 I got recently, I had to do some TLC to get it going again but the engine has a rattle sound when it's running. I asked the seller about it and he said all the IH cubs he's had do that, they call it the "Kohler rattle".

I was doing some googling and it could be a number of things. But most people say they've had K-series run for 20 years with the rattle. Some people said even freshly rebuilt engines have the rattle. Is this normal?

The front PTO clutch is not installed, could that cause an issue with the balancing? I just don't want to be going one day and sling a rod or something...

Congrats on the "102"! The common clunky rattle on the old Cubs is from the sloppy, possibly worn out drive clutch mechanism. I'm sure the "anti rattle springs" are missing in action and the clutch disc holes are a little oversized. Other causes include; PTO clutch knocking around in the pulley basket...you said the PTO clutch was removed. You could have a rod knock, cam gear gear/shaft with too much end play. It is an old tractor that may have issues that are not impossible to correct.

This is the first time I'm hearing of the "Kohler Rattle"

Guess the first thing you need to figure out is if it is the engine, the clutch, or the transmission.

You state that the front PTO is not installed, so that's ruled out.
Having it off is not going to effect the balance.

It's possible it could be the drive clutch, I haven't yet took it for a drive yet since I need to change the oil. The carb was leaking bad so there is gas in the oil. Could that cause the rattle? I know low oil pressure can cause a knocking sound...

Non pressurized oil system....good ol splash loob ree kated. ( ol' George speak)

I'm hoping an oil change is all it needs! I got a fresh jug of SAE-30, per the manual lol

Oil changes are always recommended. It may be an old machine, but with proper repairs and maintenance it will be a fine little tractor. :beerchug:

If you have fuel in your oil, you're not going to have sufficient lubrication, which will cause a variety of noises.

Perform an oil change and see if it sounds better.

Oil change completed but the rattle is still there. And she smokes a bit, mostly when throttling up. This engine has likely never been rebuilt I suspect, so it's 60 years old all original...

set the timing with a timing light . s mark on flywheel mark it with paint or something visible adjust point gap to correct timing . clean or replace points first