Well... Going off the chat in the Tome of Decay, which basically states that at Size 7 the Strength and Toughness is 50, and given that a Legion Combat Bike is a Hulking (aka Size 5) the Strength should be a 30, which to me make no sense what so ever due to the fact that it is still a piece of metal and daemonic essence so I would say the Strength and Toughness should be at a 40.
Moving down the the Wounds, I think it should be about 30 Wounds, if you follow the exponential growth of the thing. I didn't do the math needed to give an exact number that the graph would follow but I ballparked it in saying that a bike that is meant to have a Space Marine on it makes sense.
The Traits would be the same, Auto Stablized, Machine (X) and Daemonic Engine (X) (Equal to twice the Binding Strength) and fear (2).
Alright.... Assuming we put a Fleshhound into this beast of a machine, Flesh Hounds having on average these stats.
So... The 'stats' of this bike would be, if I did everything correctly would be.
Fleshhound Daemon Bike
Tactical Speed 13/26/39/78
Armor: 20 (Due to the base 14+6 for Machine Trait)
Traits: Daemonic, Intergrated Weapons, Reinforced, Daemonforged, Daemonic Engine (X)
Talents: Sprint, Ambidextous, Independent Targetting, Two Weapon Wielder
With these stats
This is a VERY rough idea of what it MIGHT end up like... atleast this is the bare mininum before we decide if we are allowed to add Daemonic Engine weapons on it, like the Hellram and such.