Hi KYF,
firstly, have you advanced the timing on the motor through the TEKIN ESC? If so, put it back down as this will increase motor temperature. OK, once this is checked, you need to adjust your gearing!
The first thing to learn is that recommended gear ration from motor manufacturers is JUST a STARTING GUIDELINE! It is not the final word! WHAT is much more important is your motor temperature. Each motor is made to work well in a certain temperature range (check the manufacturer recommendations for your motor to find this) and it is YOUR job to keep it in there, whatever you need to do. Generally, there are a few things you can do to lower temperatures: Install heatsink and fan on motor, cut holes in body for aeration, but the main way to adjust temperature is through proper gearing!!! And I believe you are now at that point (if you have covered the other two).
So presently you are running too hot (100ºC)? Lower your pinion by 3 teeth (increase the gear ratio) and see how that affects the temps. Still too hot? Lower again (or increase the spur to 84T or even back to the 87T) and test. Once you get your motor temperature to a good operating level, you can adjust the gearing to your preference (for more or less torque/ speed), but always staying within the suggested temperature range for the motor...
the way I test temperature is I run the buggy hard for 2 minutes, then pull over and test temps. If it's no good, I stop and lower my gearing. If it's OK, I keep going for another 2 minute (4 minutes total) and then check again. If it's OK, I go for another 2 minutes... I do this untill I reach my planned running time and the motor temps are still ok (in my case 6 minute mains; but for you it could be 8, 10, 12???).
So with all this, you should be able to get the motor running at good temps, unless the is another problem (ex: faulty motor or such).
Hope this helps!
