If you are pulling all the taps I'd use the garden hose to flush it then rewash with meths then allow to dry somewhere warm. If you use kerro/parafin snd tip it all out before refilling with petrol the dilution will be such as to make no difference to the bike at all. I had a mate who ran his Standard Vanguard on kerro for a bit before changing the the cheaper mineral turps. Smelt lovely running. He just had to get the motor hot on petrol before flicking to the alternative fuel.
