motor oil

first off, our crankcases are lubed by the fuel/oil mix, these arent 4 strokes,
our gear box/clutch is the only thing that takes oil

i use mobile1 full synthetic 5w-30
as recommended by driveline performance clutches
 
In low temps 10w 30.

Ok to use higher viscosity in warmer climates but clutch may drag some until operating temp is reached.