on a resent ride around oz i noticed that sometimes on starting up my old softail  in the mornings would push the dipstick up out of the oil tank anyone got any ideas why  only does it some times 

The primary cause of a push in rubber bung type dip stick being pushed out is ring blowby that can not be vented adequetly by the breather circuit, this causes the whole internal system to pressurise and the only way out is via the bung , another lesser known cause is a restriction in the oil tank to engine vent line but this usually only manifests itself after the engine has run a period of time ,the reason for this is that the pump returns 20% more than it feeds,part of that 20% is air and if the vent line is not clear pressure builds in the tank.Efectivley the whole internal system is in vacuum by design, that is why when the engine is running and the oil tank filler cap removed you can hear sucking and blowing in the tank as the system is now no longer sealed.
Top breather engines handle this situation better as the umbrellas open with any positive pressure in the circuit and are not reliant on a timed breathing event as in 1991 and earlier BT engines, that is presuming the system is in a sound operable condition.

thank you mr hoodeng for your reply i have noticed that the oil level in the tank in the mornings is slightly lower when cold  than  after start up and thought that it was leaking into the sump .in terms of ring blowby the engine used 600 mls of oil in 9700km riding hard 2up in hot weather. you mention a possible cause maybe a restricton in the oil tank vent line i will investirgate this possibility a little more. once again thanks for your reply.

I hope the 9700km wasn't on the same tank of oil!!!!!

pretty fucking hard to do an oil change and filter half way across the barkly

shouldn/t let engine oil go past 4000 klm's max even if you change da oil in da tank on a big run & leave da filter ,  iv'e done that a few time's ,  where's Barkly

4000kms you got money to burn man. you'll wear the threat out on the drain plug .wheres the barkly you need to get more.

Mine is done every 5000kms without fail! Whats $100 for the sake of my engine. I use the Scavenger, and my oil comes out as clean as it goes in!