I have a 1986 cr250, new top end, and some new things on the bottom end ( like the pump and stuff)

anyway, one day it was riding fine, but the next day it ran like crap, it started and stuff, if u put it in to first gear and give it gas it would pick up really slow, and take about 20 seconds to even start to go like 10 mph, even if u go threw all the gears, speed still stays the same, as if it wasnt even shifting

also The kicker skips, like it dosnt always turn the engine over, it just skips