An '01 that hasn't had a wrench on it needs some wrenching.
Does that mean the suspension hasn't been serviced? If so, expect it to be mostly ruined. The unitrack knuckle and swingarm bearings need to be taken care of....a few years ago. These things (kdxs) off the showroom floor need to be serviced when you get one of 'em home.
The steering bearings fit in the 'never been done' category, too? Way past time to do that, too. Chances of the lower bearing being any good are about zero.
Certainly it's due for rings...and if you're doing that, might as well off the oem (Pro-X) piston. They are known problem spots in the 220. They break! Yep..in stock trim bikes, too. When they do break, the subsequent damage can be awful.
You will need a piston kit. Make sure you have new circlips, wrist pin and rod (small end) bearing. You will need a base and head gasket, too.
Does the KIPS even still work? If it runs well, it probably is. Part of a top-end job is cleaning that up, too.
Your shock should be serviced. The fork oil needs to be changed.
Sorry...but you don't run a dirt bike for three/four years with no maintenance and have any reasonable expectation of not having failures related to it being poorly taken care of. I'm assuming there is some riding going on during that time period. ;)
Both front and rear wheel bearing sets are likely shot.
Probably a good idea to take a look at the front chain guide (the black one..commonly called a slipper). Check the rear one, too. They do wear out. When the slipper wears out the chain is going to eat your swingarm into waste. When the rear guide block wears out it's going to wreak havoc on your chain...because the bolts that hold it in are going to be exposed and rubbing on the chain.
If you haven't read thru CDaves JustKDX site, please do. It's linked in the 'Every kdx rider should read...' thread stickied to the top of this forum.
All of this stuff (dirt bike maintenance) is going to be ridiculously expensive if it's all relegated to a bike shop.
Time to buy a service manual and spend some quality time with your 'new to you' and previous-owner abused bike! :ohmy: