If it fired that easily after several years abandoned - you have a winner!
It sounds like the description of mine when I bought it in 2003 - lots of 'deferred maintenance' (neglect, such as loose and squeaky wheel lugbolts) but fundamentally sound. Easily restored. I spent a month buying and installing minor stuff like headlight assemblies off ebay, a battery, Thermostart module etc. Now 13 year later it has needed nearly nothing since. The only Yanmar part that comes to mind was a 75 cent rollpin that keeps the gearshift lever from revolving.
That's not counting my own user abuse such as ripping off loader hoses and the oil pressure wire driving through brush, but those don't reflect on Yanmar. Likewise my experimenting running 100% biodiesel. I eventually had to replace the injectors to restore easy starting, clearly their first replacement in 30 years.
Compared to the problems some people have with brand new tractors this thing is night and day better. I attribute it partly to the simplicity - no fuel lift pump, no fuel shutoff solenoid, no thermostat, only two cylinders. There are simply fewer potential points of failure. What's there was built to run hard for years and years. My cousin listened, looked under the hood, and noted that's the same engine they had in a small commercial fishing boat in Alaska - where reliability is the most critical attribute and it may run wide open for days getting home. After a little research I found Yanmar did indeed sell this engine in a marine version and it was widely used by fishermen in Japan, and for repowering sailboats etc here back in the day. These things are classics of industrial design same as that 8N. I later bought a smaller Yanmar to fit under my orchard trees better but the YM240 is still in use too. Yesterday I backhoed out several stumps with it. You have a keeper!