jetting for yz426 with full jardine exhaust


this is my first thread, and actually this is my 1st bike(came from quads). I have a 2001 yz426f thats stock other than suspension, triple clamps, and a flywheel weight. I just bought a jardine rt-four full exhaust system for it. I would like some input from the other users who have this on their yz426 what size jets, where your needle is set, and where the idle/air screw is set. I did search for a thread that had this topic, but came up empty handed. You all seem very knowledgeable(alot more than the yamaha forum at atvconnection) and appreciate any and all replies(unless condicending or belittling :applause: )

thanks alot


Hi, y'all I'm new here and have the same bike as AnimalMother85 and hoping someone would answer the mail...

Have a question also: would I be better off leaving the bike bone stock or changing out exhaust?

Currently I love it and don't have touble with starting, stalling, burbling, runs great.

i got a t-4 but not on the bike yet ill get back with you and let you know how it is

alright, thanks, anyone else?

I run a full FMF Ti system (w/ Powerbomb) on my '02 426. I ran the stock carb settings first, but it ran a little lean. I played around a bit and ended up with this combo: going fatter on the main 1 size (165) and another half to 3/4 runs on the air screw (2-2 1/2 turns), the rest of the settings are stock. This seems to work for me, So Cal temps and anywhere from 500' - 4000' elevation.

The FMF system is definitely a rush, but in all honesty, I think I still prefer the smooth, broad power of the stock system. The FMF comes on abruptly, and revs to the moon, but its fun (and loud). Stock is nice and smooth and manageable.

Just my .02

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