Oil.

I've stocked up on motor oil since I use the same one on all my OHV air-cooled motorcycles:

Normally, almost three of these go into the Commando's oil tank, however this time I'm pouring about half a pint altogether down the pushrod tunnels before I bolt the exhaust valve covers on:

This is to help the cam and followers during the first start. After the engine has ran (hopefully!) I will check the level and top up as needed.