Hey you have a crf70 and its just extremely slow it never was this slow it was way faster you can shift gears fine but its so slow you have to keep it in first or second gear to even get enough torque?

its probly the piston rings that are bad...you can take it to someone to have them replaced or take it to some one you know, or just do it yourself if you know how...after that make sure your caburator is cleaned out good..then clean your air filter and put a new spark plug in it.. it will run as good or better than b 4 he has a very good point.. but i would start with a plug air filter and clean the carb.. a little dirt can be a big drain on power... if that doesnt work then move on to rings and while you have it apart you might consider replacing the piston while your at it depending onhow old the bike is