Great engine, stomps the yx125 and the yx140 I weigh almost 240 and this thing pulls me no clutch slippage (six plate clutch) easy access to the top end with the o ring setup fit perfectly into a crf50 style frame although my skid plate (bbr) didn't match up to the head, you have to custom mount the oil cooler which isn't hard. The only thing I recommend is having your rear wheel bullet proof it tore my ten inch wheel apart. As far as speed goes I'm right around 55-60mph running a 16 and 37 tooth pattern. Overall a great engine!