I have a 83' XR200R. The stock main jet is a 138. I have removed the snorkel, baffle, and cylinder was bored out .20 over. I changed the main jet to a 145, but I can put the choke on half and still hold it wide open for about 10 seconds until it starts slightly missing(thats why I think it very lean, also engine runs very hot). I compared the 138 to the 145 and the owner before my must have drilled it out because the whole is bigger then the 145. If I go up to a 158 would I be getting closer to where it is jetted just about right? Also why would I have to go up this far on the main jet?
PS: The pilot is stock and the needle set to stock position.