Welp. Finally decided i wanted rid of the oil stains on the top of the motor.
Hosed the whole thing down with engine degreaser after removing the covers, tank, seat etc etc...
Here's the good part...
I went to my favorite gun store, bought a handle and bore cleaning bronze brush the caliber of which fit nicely in my fins and scrubbed away. Motor looks like new again on top
So that's my tip. Gun bore cleaning handle and brush to scrub nasty burnt on oil stains between fins.
You can always take a paper and pencil and do a rubbing to have the spacing in hand when you judge which caliber brush to buy.