I have been told that carrying out your own service will void your warranty even if you use HD parts, is this a fact?

Are you a licenced mechanic?

My bike was nearly 12mths out of warranty when it did a crankshaft . Dealer servicing at correct intervals was a major contributor to Harley Aust picking up the entire bill to fix my bike 100% .

Just do what most bike/car/truck/tractor etc owners do - Stick with just the basic recommended dealer services till the w/tee period is over and then do your own thing & never go back?

It also has a bit to do with km's travelled -- if you aren't doing too many, you are hardly paying too much to your dealer (as the bike sits at home more). And if you are doing big km's, seeing the dealer for two years to ensure warranty is intact, well as much as these things can be intact, get the work done and build a relationship isn't money wasted. 

So i priced up the parts and oils.. under $100 for me to do it, HD Quoted me $419 for the service??? My car has more oils and take longer to service and it cost me $180?? Please explain.

Bringing your own engine oil can help. And most have a loaner bike -- you can ride a few different HD's in the range for a day for nothing*.