Help honda atc 200es
 

so i picked up a Honda 200 all original complete with original ownership. ya i was excited lol. so after completely blowing it apart and fabing a new exhaust off a 200x i started it, it wouldn't idle properly if i put the idle to the proper spot it will sit there for awhile then spike as if the throttle was left wide open. if i turn it down to decent i have to hit the throttle every so often to keep it running. i know it need rings because when i start it it doesn't pull my arm off like they normally do lol. i heard i rumour that with a new exhaust like that id need a bigger jet in the carb. however i took it down to the small engine shop and he told me they were crazy and i needed to set the valves. i did so and now it wont start at all. aany ideas whats happening. is it just my rings?