Tapping the Backplate: Although there are folks who recommend drilling through the upper left backplate mounting screw hole with a 1/16" drill, I will not recommend that method, as for me, it leaves too great a risk of metal shavings (small though they may be) being left in the counterweight and bearing/lower conrod bushing area of the motor. Not good. Rather, I suggest that one simply use a DuBro 6-32 pressure tap and drill the backplate after it is removed from the motor (any place where there will be room to install the pressure fitting). Then, simply install the pressure fitting using some permanent-type Loctite, the washer that comes with the fitting, and make it snug. After the loctite cures a bit, use a dremel grinder wheel (or cutoff wheel) to remove the excess threads protruding on the inside surface of the backplate. DO NOT FORGET TO DO THIS!!!! Wipe everything off, and reinstall the backplate. Done. No risk of metal floating around in the motor. This is from:

http://www.rcaerobats.net/OS160_Setup.htm