Thunderbird Twinspark 500cc Launched by Royal Enfield By Deepak - January 5, 2012 Royal Enfield has not launched Thunderbird Twinspark 500cc today at the AutoExpo. The 499cc Twinspark OHV engine will produce 27.2 bhp power @ 5250 RPM and 41.3 Nm of torque at 4000 rpm. Royal Enfield Thunderbird Twinspark 500cc Specifications