They are or were German?
With a bit of luck it might just be a German-built version of the ubiquitous Honda-clone?
Companies all over the world tend to buy the same components and put their own tinware/plasticware and paint on them
I own a genuine Honda 2.2kW genset, two Honda-engined Chinese gensets (7kVA and 4kVA) and three or four Chinese-built generators with Honda-clone engines and various outputs 2.2kW to 9kVA
They're all just larger or smaller versions of the same thing. Once you take the tank off and have a look you'll see how it works. There's nothing very complex in there
If you paid $100 for a Honda carb you could probably have paid $40 for a Chinese carb? Either seem to work OK
At my work we have one of the 2.5kW-ish units in each of our field service utes. They work hard powering air compressors and power tools and they get little maintenance. They're pretty tough
If you take a couple photos and that old carb and wander down to a company that actually services generators, they'll tell you straight away that there is an endless supply of cheap (but of acceptable quality) engine parts for these.
Engine-wise none of mine or the ones I service at work have ever needed more than a six-monthly oil change or a new carb ($40) or - in one or possibly two cases - a new ignition coil ($30)
You won't have any problems keeping the engine going
If you're lucky, the generator part is a Chinese one with a German paint job. Then there will be parts and service available everywhere
Of the six generators we have at work, some with many hundreds of hours on them, the only non-engine parts I have replaced have been AVRs - a five minute job involving three or four 6mm bolts, a couple of 5mm bolts and one plug. AVR's about $40-70 depending on the model?
You might like to remove and flush the tank, the fuel tap and fuel line as well?
Good luck