Don't get me wrong I am in no way puting down k&n filters. I'm stating they are not made for rc. take a little piece of sand it won't hurt a 125cc engine but you have to remember one thing these engines are around 2.5cc. As far as rb inovations they make a supercharger kit for $180.00 that gives you .01 hp gain, not the most trustworthy people IMHO. But hey if you want to use it go for it not my money your throwing away.