Why are dyno runs made at 4th or 5th gear? Why not 1st or 2nd?

 

the bike revvs out to fast, you get a more accurate reading when the bike revvs slower, thats how the dyno is set up.

 

wrong.

The gear a bike is dynoed in varies by bike. A banshee for example is typically in 5th, a honda in 5th, a 4-stroke in 4th. Too much load (say 6th for a banshee) can kill the bikes power because it simply cant spin the 500lb drums efficiently. A short geared bike spins the drums too fast with doesnt build heat in the pipe which doesnt make power.

 

thats basicaly the same concept i said.