I was wondering how much porting would change my engine timing and if it would require increased jetting?

 

Engine timing? Do you mean port timing or ignition timing. The ignition timing is independent of any head or cylinder modifications. Typically though the timing is adjusted to better compliment the new head mod's or port timing mods.

An increase in jetting. Yes, typically, everyone's port work is different, so how much differs. By porting the cylinder you're getting it breathe better, and if your porting a cylinder head, you're doing the same thing.

 

I agree with Backcountry if you're porting a 4 stroke.
If you're porting a 2 stroke, it might change your port timing depending on how you have it ported.

 

Port timing is controlled by a cam on a 4 strokeand the piston on a 2 stroke by cutting on a 4 stroke it dosn't affect the cam timing.But on a 2 you can lower the ports that will change it