Ive got a 4.5 tonne camper that runs an asthmatic pushrod 3 bearing cranked
2 litre all cast iron dinosaur. The diff is wait for it 9:1 ratio and it has
a crawler gear in first of 6:1 or something in case it needs to go up very
serious inclines or get off the mark with the weight. Its been round Oz Twice.
Thats 105hp 125lbs torque pulling more close to 5 tonnes. It overtakes semis at
140kmh on a slight incline uphill and revs maybe at 4000rpm at 100kph cruising
with 16R LT tires. Divide 5000kg by 10 = 500kg engine size = 200cc it must be all
in the final gearing. I guess like if the car has a 4.5-5.11 diff ratio the bike engine
will be pretty good getting off the line or pulling more weight than its designed for.

A hayabusa makes max hp at 9500rpm as I remember with 1300cc so with 4.7 to 5:1
It will be magic with the right diameter wheels.

A 2006 Kawasaki Ninja ZX-6R makes 100 kW (130 hp) @ 14000 rpm
48.1 lb·ft (65.2 N·m) @ 11,500 rpm so would need at least a 5.1 final.