cornolio, glad to hear from you. I also had issues with stripping the plastic Kyosho spur gears, so I swithced to steel spur and a hardened pinion. I have been running these on all my brushless conversions with no problems. The important thing is you must use a Mod 1 hardened pinion, which RC-Monster, Impaktrc, MegaUSA all sell. I am also using a wide Robinson Racing Losi spur gear that is wider than normal and spreads the contact area out more, which improves wear on the spur and pinion as well.
http://www.amainhobbies.com/product_...ducts_id/12711
Spur comes in 47, 48 and 49T.