Does anyone know how often you have to change the oil on the crank side of the motor?  

You want to change the oil every 3 to 5 tanks of fuel.If you are only changing the oil tank and not the crankcase, then you aren't removing all the contaminates. You dont have to change the filter everytime, (every other oil change should be sufficient), but you should always change both crankcase and tank at the same time.  

Thanks for the help raptor man.  

No problem,anything to keep us all riding!