Interchangeable parts

[Eddies 680ds]

Substituted OK so I purchased a Baja 650 or out 30 over and everything is on the up and up. Except there are no places around where I live to buy parts even such thing as there’s no air filters the right type of oil etc. But I hear that they DS 650 can be changed or Substituted 

[Eddies 680ds]

I’ve read somewhere recently that BMW was about identical on a lot of things such as oil filter, starter clutch etc.