1980 KZ250 Ltd Carb probs

[jomama]

HI, I have a 1980 kz250 that I put a K&n air filter on.(one that bolts right to the carb) They disco-ed the orig. air cleaner. I am thinking that It doesn't neccaserly need rejetting, but I'm almost sure it needs some adjusting, it is hesistating and back firing a little. I have read that on some keihin carbs you can drill out a plug to get to the mixture screw, does anyone know if you can do that to this carb? How can you tell where that plug is? I know it's Keihin but I'm not sure how to tell what model of carb? I don't want to just go drilling holes in my carb. If it does need new jets how do I know what size to get? Thanks

[FPMXer]

With that K&N air filter on there it's breathing ALOT more air than with a stocker. Pull the plug and check it's color and condition. It's most likely running lean and the plug should be dry and lt brown. If so you either have to jet up to the fat side or move the position of the clip on the needle down one from the center clip position. But chances are you need to fatten it up some with the amount of air the bike is now breathing.