Check the reeds too man, your dad is right because reeds will do that as well... I forgot to add that. But anyways those YZ250F's are nice they are faster than a regular YZ 125 and better for racing, but if you wan't to do FMX and hit big jumps then I wouldn't prefer one. Some people do FMX with 4 strokes but I am more of a 2 stroke person because those YZ250f's need lot's of care, it's not like some other XR or other 4 strokes where the engine won't blow for a year or more, these will blow engines almost as fast as 2 strokes I hear if you ride them hard. I always just stick to 2 strokes, but that doesn't matter because it's what YOU wan't not me so your best bet is to go around and find people selling them and ask them to test ride one and ride the 250 F"s and the 125 two strokes so that way you have a feel for all of the bikes. I you go with a 125 then I prefer a YZ, they have more power than the CR's do because the engines on the CR's are gutless and have no power at all but are more comfortable than a YZ and the suspension is a bit better. Just remember though, it's 10% bike and 90% rider. If you got any other questions then just ask and I will answer, hope that helped some.