I have a 98 Warrior that I got used. It has had mods done to it. Bored and gone through, new air box, upped the jets.....etc. It runs good at low RPM and high when it is cold. When it begins to warm it develops a intermitent miss. Breaks up pretty bad. The bike was running rich and needed floats adjusted. Did that(had a 150 jet - too rich went to a 147.5 seems to be right). Throttle response is better but the miss / break-up is still there. Does this point toward ignition or Timing / Valve adjustment. I know that the mods are not helping the diagnosis but this is the info I have. Any help would be great.

 

You may have a plug with a bad gap or a dirty fuel filter. Lets start easy.