Pinion size with 6.5 Speed Passion

[fmo]

I have been running my DEX 410 for the first time last weekend at an indoor meeting and realized motor temperatures close to 100 C after a 6 min run. The ESC was quite cool at approx. 40-50 C compared to the motor.

Motor is a Speed Passion V3 6.5, ESC is the Speed Passion V2 GT PRO.
Pinion size was 18 teeth.

What pinion sizes do you use in your durangos with 6.5 motors?
Can the motor overheat due to a small pinion?

Thanks for any advice,
Frank