The one on the left (while looking forward) is the HST filter. The factory must paint the orange HST filters to match the hydraulic filters for looks, cause my dealer said it's orange. When I scraped the paint on the original HST filter, it was orange underneath. Also, sucks when they refer to the wrong plug in the book. Details matter.
The wrong filter used had the part # for the Kioti 4510. I just serviced mine for the first time and I’ll say the owner’s manuals are a little confusing at best. It wasn’t real difficult and it should go much easier with less spilling the next time.
My 2014 dk40 hst held over 14 gallons! A little bigger than the newer dk 4010 models. The rear hydro filter was a muther to get off. They must have a 900 lb gorilla tighten them down.
When you first did the hydraulic oil filter did you lose much oil? About changing the hyd oil. Bigger equipment users will send a sample of the oil to a lab to test for particulate and the base additives. They do it that way instead of by hours because if the oil is still good they save a bundle by testing.
on my ck3510 there are hydraulic hoses blocking the hydraulic filter. When I replaced the filter, the tight hoses prevented me from unscrewing the filter. I was able to eventually get it off, however, it was a nightmare trying to get the new hydraulic filter threaded on correctly and fast. I lost 1 gallon of hydraulic fluid trying to get it on because the tight hoses were in the way. I was swearing at the top of my lungs. Hated the whole experience.
Kioti has THE WORST manuals I've ever seen. I own both a Kioti tractor and Kioti Zero Turn Mower. Both manuals are useless, especially the one for the mower. It had completely wrong instructions for removing the mower deck. However, they are both very sturdy, reliable rigs and the price was right, so I'll cut them a "little" slack.
My 2022 3510 does not require HST fluid change until the 400 hour mark. The 50 hour thing is ONLY for the HST FILTER, NOT THE HST OIL. I have NO IDEA why you are changing out the HST oil at the 50 hour mark. That explains why your "old" HST oil looks close to pristine. You are wasting your time and money.