I have a full stock Kodiak 400 auto and I am about to begin the upgrade process. I want to install a new K&N filter and FMF pipe. Do I need to re-jet when I perform these upgrades? With both or do I need to re-jet with any particular one? If I do, how do I go about re-jetting? Which jet do I use or how do I find out which jet to use?

Thanks.

 

Most likely...yes.
Especially if you plan on running with the air box lid off.
The easiest, and most effective way to jet, is by the symptoms of drivability.
The things you plan on doing will lean the current mixtures, so youll need to go richer.
Heres a good article on rejetting, and describes how to go about troubleshooting the symptoms.
http://www.motorcyclecruiser.com/tech/jetkit/
Usually theres a guide sheet or a 800 number you can call, for baseline jetting changes, that come with the pipe. Its a good place to start, and fine tune from there. Lots of people try reading the spark plugs with a plug chop, but seeing how you have a automatic, a plug chop isnt gonna be easy or effective. If it isnt done a specific way, the results are meaningless. and then add to that, all gasoline has so many additives, that mask the results on the plug, that reading plugs can be very difficult at best.