Chainsaw Repair

Interesting thoughts.  I remember working with the portable mill guy when we milled the macrocarpa (cyprus) to build my house.  He had a 154 I think with a shortish bar that he called his limbing saw.  A few years later I bought one from a friend.  Heavily used and beat up looking,  but the engine pulling really well.  I'm wondering if the oil pump capacity sets a limit on bar length?  Perhaps the limit set by horse power or ergonomics/balance comes up before that?