if i buy a white brothers e2 exhaust do i have to change the jets on my stock 300ex and how hard is it to do this if i have no idea how

 

Yes! Honda jets lean at the factory to meet emissions standards. You put a pipe on and it is going to pass more air and therefore be even more lean. A lean engine runs hot, and you can damage your engine!

I would also mod the air intake at the same time. Maybe a UNI air filter, and vent the airbox lid with some of those round 1" UNI vents. You are adding more air, so you need to add more fuel in to keep the fuel/air ratio correct.....

Jetting is more art than science. You start out rich and then go down until it just begins to run lean, then back it off so you will insure that you are never lean. The carb has several different circuits that come into play at different throtle openings.

Read about carb theory: http://www.dansmc.com/MC_repaircourse.htm

 

thats a great link!

 

so how hard is it to change the jets

 

Changing the jets is easy but getting the right size jet takes time. Like ReconRanger said, it's more art than science. The jets just screw out and in with a flathead screwdriver.

 

the white brothers e2 exhaust comes with recomended jets

 

Then try em' out and see how she goes!