Castle Creations motor and ESC combo recommendations for the Arrma Kraton 1/5th scale.

Cobra 6 w/2028-800kv - 32T pinion/47T spur on 8s = ~42MPH
Cobra 5 w/1721-1260kv - 22T pinion / 47T spur on 8s = ~45MPH
Cobra 5 w/2028-800kv - 37T pinion/47T spur on 8s = ~48MPH
Cobra 5 w/2028-1100kv - 32T pinion/47T spur on 8s = ~55MPH

Note: All speed estimates are with stock tire diameter, high quality batteries and appropriately sized battery connectors.
Always monitor ESC, motor and battery temperatures on new setups or when changing gearing or batteries.