Nothing wrong with that model Petter, but parts are of concern... check out the condition of your machine before jumping to any conclusions.
I would agree with that assessment, and would add the following:
The PJ is an enlarged version of the Petter PH engine, but there are significant detail differences, there are some components that are interchangeable, such as big end shell bearings, oil pump, connecting rods, timing gears,govenor parts, and valve guides. Injector and fuel injection pump bodies are identical, but nozzles and elements are different.
For spares in the UK you might like to try this person;
http://www.petterengines.co.uk/ Jim Perkins is a retired petter service engineer and may still have some parts. The usual Indian suppliers also have parts for this engine.
If your still stuck, then PM me as I have some GENUINE PETTER 5000hr PJ2 and PJ3 rebuild kits, the catch is that all the components are STD size. I would also carefully inspect the condition of the sheet metal cowling, as these parts suffer if left exposed to the elements and are generally more difficult to find than wearing parts.
As mentioned by others a good engine, but they do have two weakness:
1),The injection timing is supercritical and if it is not spot on these engines will smoke even when warm.
2), The inlet valves are shrouded, and thus pegged in position to prevent them from rotating, hence they do suffer from valve stem wear.