Changing exhaust

[maxi81]

Just wondering how does changing an exhaust pipe affect the jetting? For example going from a stock exhaust to a pro form exhaust.

Thanks

[sleepy]

Good question. Bit like going to doctors for a diagnosis without telling him the symptoms.
In other words there is no way to know unless it is a common bike and a common pipe, even then there are so many armchair experts you would get 50 different answers. 

[80-85 husky]

4 strokes usually -- loosely speaking may go up a main jet size or two as accessory pipes tend to be freeer?? flowing at higher revs...need more main jet fuel. two strokes can need changes across the board? but usually a clip position and 1 or more mj sizes at max. as above each pipe and engine needs looking at. most get chucked on and the noise changes making most punters think thats more go...