Gear ratio for 90 nitro plz

[RossoOz]

Howdy, just after the gear ratio for the bergen 90 nitro machine. I bought a second hand machine without any instructions. Just trying to set up the futaba gv1 gov with the right gear ratio.

Im assuming that the previous owner has keep everything standard.

Also, whats the sweet spot for head speed for this machine?

I'm running a os 91szh with MP2, 690 blades.

Cheers

Rosso.

[cbergen]

You may want to count the teeth on the pinion. These machines can be had with a 10,11, or 12 tooth pinion.

The 690's may be a little short for that motor with what should be an 11 or 12 tooth pinion, giving an 8.18 or 7.5 gear ratio.