proper jetting for new set up 400ex

[gimphand]

I have a 400ex, full pipe, K/n Filter no lid, NGK 8 plug, just bored to a 416 with xr400 gasket. Now that I put this back together with new piston should I rejet? I put a new plug in I had laying around and it was an 8, the old one was a 9. Ran it for about 15 minutes and the plug is had some white ash?

[krt400ex]

you need to rejet. start with a 155 main, 42 pilot, 2.5 turns out on the fuel screw and see wut happens