hello guys, i m going to buy a rcmk gas engine,i ve few questions that what is the best thing of SX 254 evo over a s254 evo?i know there is water cool crank case in sx.does it really give better performance?both their hp are same though.any response of u guys are apreciatted.

The SX crankcase is BILLET where as the S is a casting. BOTH have 4 main bearings and all parts interchange between them.
IMO no power difference ...

For the racers within NAMBA, because of the billet case an SX is a GX-1 class, where the S engine is a G-1 class.

thanks scott.it seems no significant advantage of sx. in my state,there is no engine classified race,as long they are 26 cc.but sx billet crankcase looks nicer.still scratch my mind to choose which 1 engine.sx need to pay more.