Veteran quality, cavalry speeds, treat them as cavalry instead of infantry except where it would be amusing to watch a breakdown or explosion.
Explosive charge: One use only, front only, range=close assualt. 6FP, and any 1s rolled are rerolled against the motorcycle instead (backblast). These dice are rolled in close assault and the results applied before the regular close assault attacks are rolled. If you have special rules about who attacks first in close assault, I suggest starting with the longest weapons first and then by decreasing length.
If you're using points, add 1-2 per weapon to cover the first-strike type ability.