dex410 gearing

[jake1*2011]

wander if anyone can help, I've got a 5.5 turn motor in my 410 and at the mo Im running a 87 tooth spur and 21 tooth pinion, which the motor and speedo are running quite hot, hot enough where you can't hold your finger on them for more then 3 seconds, what gearing should i use to eliminate this problem? Should i be thinking of changing the spur?