If I recall correctly, I was informed that the PN Racing Speedy BB is a 52T motor and the Kyosho X-speed a 50T motor. I currently own two Speedy BBs. One is in one of my older F1s and the other motor is in one of my newer F1s. Neither of those F1s have FET upgrades and thus far I have had no problems. Although I have been told that some people have had problems with MR-02 boards when using either the X-speed or the Speedy BB, I have X-speeds in all my MR-02s and I haven't had any problems with any of my MR-02s. Although I haven't used the Speedy BBs in my MR-02s, if I attend the PN Race in Rialto, California next month, I will either be using the Speedy BB's or the S03 (FET required) depending on the class since PN Racing will be handing out the motors.

http://www.pnracing.com
http://www.kyosho.com/cars/kyod01x4.html