2001kx125

the guy who sold me my bike said the previous owner had an aftermarket pipe on the bike but had reinstalled the stock one becuase the aftermarket was scratched/banged up.

the bike ran like crap sputtering and bogging

i moved the clip on the needle (that goes into the jet in the carborater) from the bottom most (most gas) position to the middle and it ran better but still some sputtering/bogging, so i moved it to the 2nd from the top and it ran good.

the bike has a pro circuit silencer and pro circuit stickers so when i went to pick a pipe i got the pro circuit works pipe.

i got that on and moved the needle clip back down to the bottom most position and it ran like crap again, the position i settled on was the middle, (1 down/more gas than it was on before i put the header on).

I was under the impression that a pipe/expansion chamber did alot for a bike and if you couldnt get enough gas by moving the needle all the way down, you would have to "re-jet" it with a bigger diameter jet and correspondingly thicker needle.

Does this small of a change in carborator seem normal???