hi, You can upgrade with XR200 bike parts, camshaft is a good thing by memory, increase your compression with 200x piston, porting your head a little bit and open a little exhaust is good, the best thing is port matching. increase your carburetor size to match with your intake and re-jetting. run with 91 octane is good. make sure that automatic timing advance is very clean and not loose, replace it if it needed, ensure your timing chain , tensioner and you chain follower is in good condition, that important.
its a good start i think