I am buying a new HMF slip-on muffler for my 2002 400ex. I know that I will more then likely have to rejet. I don't know anything about doing it. Everything I owned was fuel injected. How hard is it to do and what all is involved? Do I need any special tools? Sorry for such a stupid question just never worked on a carburated machine. Thanks in advance for everyones help.

 

Itll make the mixtures leaner, so youll need to jet up. All you need is a few hand tools.
Youll need to remove the carb, turn it upside down, and replace two jets. One uses a 6mm hex, and the other is a slotted screwdriver. Make the main jet, at least 2 sizes up, and go 1 up on the pilot jet, put it back together and fine tune the mixture screw.
Heres a real good article on jetting, and how to jet by drivibility symptoms.
http://www.motorcyclecruiser.c...carburetion/index.html
Heres a pic of the inside of the carb.
The center brass piece is the main jet, and the slotted screw just above it(red arrow), is the pilot jet.
The sizes will be stamped on the side of the jets, the stock pilot jet is 38 and the stock main is 148. Just take them to the dealer, and get a few jets.

 

Thanks for your help.