XRAY - Model racing cars

Hello everyone,,
I have super awesome XB4 it is very beautifull,well made model and i like it more than rest of my auto's, but i can't resolve one problem and hope you can help me Here's the situation - this year i'm racing in beginner class. Here we are allowed to use three motors - LRP S10 blast (20500rpm), LRP S10 twister (23500rpm) and thrust eco 21 (25500rpm). I've tried all of them, but no matter what i'm having SERIOUS heat problems - after 5 min run all motors are well beyond 110 degrees (celsius), and after 7 minute final runs S10 reaches 150 on brushes and thrust eco just melts inside.....I've tried different gearing - 81T spur with 25T pinion. Also 74T spur with 25T and 27T - last combo (74/27) is somewhat competitive in terms of speed, but motors are smoking after first qualification. The only gearing that keeps temps reasonable (by that i mean ~80 degrees) is 74/22, but in this gearing i loose waaay too much speed - all the LRP blast models are faster in straight lines and what i gain in perfecting my turns, i keep loosing in straights. We are running big tracks (indoor clay and outdoor clay/sand) initially made for 1/8 nitro buggy, so straights are long enough to loose 1-2 positions each time. I was starting to think XB4 is not made for beginner race (i know, it's mod), but guy in same class races kyosho and his temps are normal, so i know i'm doing something wrong myself.
Any ideas would be appreciated.

Thank you for your post, I look for such article along time, today I find it finally. this post gives me lots of advise it is very useful for me.

Allows you to gear higher thanks to the smaller tooth count, allowing you to run bigger pinions without cutting and modifying the stock motor plate.

Includes M2.5 hardware so that it reverse mounts to the spur while allowing the spur teeth to clear the hardware.

Heavy duty machined delrin for precision and durability.