That does look like so much fun.

that thumb nail got me

Great race but you need to see about getting some full face helmets (road motorcyle helmets without the sun visor/brim/peak) as they are made for off road dirt bikes and both guys need to start leaning back at high speeds! (the brims/visor on the dirt bike helmets you are using catch a lot of air causing drag as does your chest when you sit up.

You gain more by increasing your speed when going slow (running) than increasing speed when going fast (coasting) . Train your sprinting speed to increase your endurance . Bicyclists know how to draft behind another cyclist to increase speed . Have you ever ridden the course down on a bicycle ? You will notice potholes and road surface more on a bicycle with narrow tires .