a little heating issue

[t-maxxracer32]

hey guys i got my revo off some guy on traxxas and it came perfedctly tuned cept one problem... after about 5 minutes it gets to around 225... i dont really wanna try and tune it so is there anything i can do to help this?

bigger heat sink? diff tires? gearing? or what dont know too much about gas heating!!

o ya and its an os18 motor! lol

thanks!