Exhaust and jetting 2003 WR 450

I have a 2003 WR 450 I took the guts out of the stock pipe and put on pro moto billet end cap when I took the carb off to look at the main jet size it had a 170 main and 48 pilot with this set up it had a big flat spot about mid throttle and I was more than 3 turns out on fuel mixture and could'nt tune out the flat spot, I went with a 155 main and left the 48 pilot seemed to help quite a bit sounds much better and response is crisp. does this sound about right? anyone know?

First....go here:


Second, I'd say a 170 main would be to much, yes, but a 155 sounds pretty small. I would try a 160, then a 165 and see which is best. You also have to consider your needle and what clip the needle is in. It all works together....

As a example, I have a 04, with hot cams, all free mods, and FMF, in eastern Canada at sea level, and I am running a 170 main, so I would have to think a 170 is to rich for your location, and bike

But your best bet is to go to that thread which is the WR jetting database as step #1

Thanks for the input, I will try the 160 and 165 and see where that gets me.

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