Help with 4stroke 125 jetting

[MotocrossMatt]

Hi i have a Yamaha XTZ 125 that takes way to long to warm up.Starting isnt a problem but when i want to ride the bike it just wants to die. This is very frustrating. I have drilled holes in the airbox and a custom made pipe. Im at sea level and its kinda warm in South Africa so the bike shouldnt be struggling so much. Quick reply would be appreciated.Thanks

[cornishwrecker220]

drilled holes in the airbox..aftermarket pipe...now it wont run properly...?? have you altered the jetting since you made these `mods`?? sounds lean to me....you will have to go up on the main jet, raise the needle & adjust the fuel screw or change the pilot jet for starters.

[fuzzy]

Yeah, factory 4-stroke jetting is generally very much on the lean side....Give it some more fuel.