ltz 400 39mm fcr jetting

[1capper]

I need help with jetting my ltz 400. I just got a 39mm fcr from a yfz 450 and im running a yoshimira full pipe with a k&n and 400ex intake boots.

[350ex]

Im running a 170 main jet, needle 4th clip from top, 42 pilot 1 3/4 turns out on the fuel screw. I think Im a wee bit lean by the looks of my spark plug. This thing rips though. Im happy so far. Just worked on the tuning the other day. Im 1200 above sea level by the way.

[1capper]

Thanks alot i will try this. I am also at around 1200ft elev and i also am running a high rev box but it is a pro com. Do you think the cam helped a lot? How much did the carb help? Are all the 400ex intake boots the same, or do i want a certain year?

[350ex]

Well all I can say is its a whole new animal. Its quite a bit quicker. I'm running a rev max (procom) box as well. I still havent messed with the box. I need to get some race fuel to mix with before I start advancing the timing too much. Plus Im still somewhat breaking in the rings so I dont want to rev too high. I like the cam. I was worried it would lose some bottom end but its still rock solid. Mine is the new style stage 1 intake and exhaust. I think you will like it. Just make sure you get that air flowing through that ex boot. Dont short change yourself and not modify your airbox so the boot isnt smashed by the shock mount..