I've got the 2003 P650 and just placed my orders for the black spring, the twin air filter, and the diamond G snorkel. Soon I will be doing a Nyroc muffler mod. Will I be required to do any rejetting? I'm not that much of an ATV mechanic, so hope it's not a dumb question. I will put the snorkel and twin air filter on first and then later doing the muffler. Was wondering if I had to do air/fuel adjustment immediately after or just see how it runs?

 

Yes, you will need to rejet after these mods. Save yourself the hassle, and do it all at once, so that you will only have to rejet once.

 

You don't have to rejet right away try it stock for awhile, understand your quad is set rich from the factory by doing the intake you will lean the system that is alright. When you do the muffler you can still use the stock jets try it first then go move up to a higher jet size but I recommend strongly to stay with the Kiehin jets as I have in the past stated the DJ jets are not what they are supposed to be. The largest DJ jet is at least one size smaller in volume than the stock jets already in your quad. So to go with Dyno Jets you are defeating the purpose of rejetting period. Do one thing at a time and see how you like the modds this way you will appreciate the advantages as you go.