I have a D20A-6 it's "Gray Market" the only difference being Japanese writing above the starter switch and the maintenance schedule printed behind the hydraulic filter access door. Parts for this dozer are stocked in the US and are readily available from most all US Komatsu dealers, some independents and eBay. Manuals are out of print, but reproductions can be found / purchased on the net (google it) . It's a good little machine, use it or loose it - meaning these dozer's don't like to sit idle for months at a time not being used. The steering breaks and the clutches are dry, and tend to get sticky (rusty?) over time. If for some reason I don't have a need to use the dozer, I start it up and drive it around for about 1/2 hour once every two weeks just to keep it charged and all the parts working freely. I did a bunch of routine maintenance after I bought it, rebuilt two leaking hydraulic cylinders, replaced 12 track rollers, and did some mods to personalize it. Before you buy drive it around, for at least a 1/2 hour to get a feel for it, bury the blade into the ground, making sure both tracks dig in and continue turning at the same rate (this checks the steering clutches for tension and wear. Check the rear drive sprockets, it they are pointed they are worn past their limit, if the tips have flat spots then they are probably OK. Look at the track rollers are they evenly worn? are the track roller guide edges rubbing against the track links? if so the rollers are worn past the limit. Check the track links, are they round? or oblong? Round is good flat spots or oblong is bad. Check the idler sprocket (on the front) for wear, and the track rails, how much space is left before the track rail guide reaches the end of the front rail? Do the tracks sag? if grease is added to the tension cylinders do the tracks keep their tension?
How do the track shoes look?
Here is a link to the life of my Dozer -
Larry's Komatsu Dozer CLICK HERE
I still have it, use it and love it, for a small dozer it's the affordable ticket to a crawler.
Larry