what aftermarket pipe? its important to know before giving specific advice .
Re-jetting means to remove the carb , remove the float bowl and replace the brass mainjet , and sometimes the pilot jet to install larger jets to compenstate for engine modifications .
For Example I'll use my Blaster .
FMF Head Pipe and PC2 silencer
UNI Pod Filter with no airbox
Stock Carb re-jetted with a 290 Main , stock pilot , air screw 1-3/4 turns out .
The Plug chop is done to show you what is going on in your cylinder , when you do one the end result should be a light to medium tan stained electrode insulator ( the ceramic part the electrode sticks out of ) if its really dark , and wet and gooey looking , its too rich , drop down 1 main jet size and use a NEW plug and do it again until you get that tan/brown color . If its too lean , it will too light of a tan , or almost no discoloration , and too lean means BOOM !!!! no more motor . Always jet rich , just on the rich side to protect the engine .
The main jet in a stock carb is a 230 , its easliy removed with a small six sided socket , make sure you don't lose the washer between the main jet and the jet body , IT HAS TO BE THERE otherwise it will never work right . and don't reef on it when installing it , its brass , its delicate , think of it as a egg , hold it like a egg , turn down the volume on your meathooks when installing it , ok chief? .
I never had to mess with the pilot jet , its fine , usually thats for a bigger carb OR if you are running a Big Bore on a stock carb , not a good idea so don't do it .
Needle position is also important , BUT with your set-up , I doubt you'll have to change it , mines in the stock position in the clip .
While you have the carb apart , clean that bastard , good too , carb cleaner , pull the choke apart , clean it , clean it clean it clean it , blow out all the passages with compressed air .
My best advice is this clean off your workbench , put down a dark towel ( I had a big piece of dark speaker carpet I stapled down ) so you can easily see all your parts , and small stuff tends not to just roll onto the floor when its kept like that .
also check You Tube , I have seen a jetting video on there before for the Blaster Carb .
and im from the uk hahaa 
