I have one with the YS110 , its an awsume combo . Perfect i wud say . if u use the 2stroke fx90 ull have flooding probs cause the tank is much higher than the venturi . better use a pumped 4stroke like the os90 fs11 surpass , its a pumped 4strk from os and is also a very good combo for this kit also u can mount the tank over the CG by using these motors , a compromise wud b mounting the 2strk os90fx sideways . to avoid flooding\midrange loading up. the 120 is unnessary cause the 90 anyways does the job at half throttle.