Hi
If my XL650 was really dirty I would take it outside and hose it down with brake cleaner. Brake cleaner usually requires no scrubbing.
Then i would blow it off with compressed air, then let it dry, maybe wipe it off.
After that I would bring it in and give it a good lubricating with a 0W30 or
10W30 synthetic oil($6 a liter at Wallymart).
I lubricate my Dillon 650 with 0W30 synthetic and it works slick!!
My 2 cents