Used my Ol Mule 550 for driving to the stand, but its been down these last few months, rebuilding the engine...
(previous owner went 3 years almost without a oil change)

Just got finished going thru my 2001 Mule 550 motor.

PartsPitStop.com is your friend for OEM parts.

Online microfitches so you can find parts easily.

Runs nicely now and used daily around the ranch.

I use www.babbittskawasakipartshouse.com for all my parts. Parts usually get here within 4 days. Prices average about $4 cheaper than OEM.

What did u do too it?

Rod, piston, rings, wristpin, circlips, seals, gaskets, new oil pump, new babbit in both large end of counterweight rods, new guide rod for counterweight, hand lapped valve job, new exhaust valve spring, filters, new rubber between airbox and carb, clean carb, spray some gloss black rattlecan on engine tin, clean/adjust brakes on all 4 corners and bleed, 2 new tires on rear.

Im doing, Rod, Piston, rings, oil seals, valve stem seals, put new valve guides in, new main crank bearings, new ACR on the cam.
The rings were pretty much baked.

Yeah, know what you mean.
I had a rat build a nest inside the cooling tin.
Trip down to creek was a breeze.
Trip back up hill was a struggle and it seized and died.
Luckily it was a heat seize and not a lean seize and turned over after it cooled a little while.

Top two rings were stuck to piston and oil rings were sticky.
I did do crank bearings also.

Everything else was in spec when I measured them so I bought parts and put it back together.

When you have bottom end out, you might look at the babbit on the large end of the counterweight rods and check play.
Mine was worn enough to make a little tink-tink-tink noise while under load.
Also measure the rod that comes up thru bottom that counterweight slides on - mine was worn a little so I replaced it.

Also use a good modern engine assembly lube when assembling parts.

I checked play on that there was a tad but it was in spec.

Luckily, i didn't have to bore the cylinder out! It's perfect, not a scratch on it!
Did you check for endplay on your crank?