I am cleaning out the factory oil as I split most of it on the ground swapping motors. What is the best techinique to clean out the factory oil so I can run Amsoil in it. Do not want the two to mix.

 

Remove the side covers and try to flush it out with another lube. Or get some cleaner and try to clean it out the best you can. I would just try to flush it with a different lube and then use a lil of the Amsoil to get the flush lube out and reseal it and fill it.