Do I need to re-jett?

I have a 04 YZ450F, just got a White Bros E-Series slip-on, the one with disks. I've heard that you have to re-jett and I also heard that you don't. I live in SoCAL desert, mostly open desert riding. CONFUSED! Any help would be appreciated. :thumbsup:

I just got this pipe for my 426. I didn't have to rejet at all. I turned my fuel screw out about a half turn. that's with five discs, the spark arrestor plate (duh lol), and the quiet core insert. If you run a lot of discs you'll probably have to go the opposite way I did since it'll open it up. Hope that helped. Question: is your really hard to get the allen screws out of to change the discs.

How quiet is your bike with five discs? How has it affected the power?

I got this pipe of e-bay for $100 bucks. Real clean with the discs, seller had just replaced the allen screws. How does your bike sound Kizzle?

I would check the plug color to see if jetting is ok. Any time the airflow changes (muffler upgrade,opening up the airbox,etc.) check the jetting you could damage the motor by running it too lean---better a little rich than way too lean.

BC61: My bike is quite constricted with 5 discs plus the quiet core I opted to put in it. It's no where near as fast as my Powercore IV FMF muffler. Well, on the bottom anyway. The hit on bottom is so slow.

tuekwik:The bike sounds a lot less obnoxiously loud than with the Powercore. If I keep the 7-10 (preferred for track) and no quiet core setup it's pretty loud but it's still better because the sound does not project straight out. do you know whether or not the guy that had yours before you drilled the holes before putting in new screws? Mine are SO SO SO hard to get in or out. If they were easier I'd change the discs wherever I go, but it's just too hard to do it the way it is.

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