For all you guys out there who have 400exs. Everyone says that they are jetted lean from the factory. Whats the easy fix? A bigger main jet or raise the needle a click? I'm kinda stuck on this one.

 

Since no one e;se has responded, I'll put in my nickel's worth. Yes I've heard the same story so I would go one size fatter on the main to start, with the jet needle in the 3rd position, which is the nominal position.Of course in the final analysis, the only way to know if you're jetted right is to ride & read. Ride the machine at 3/4 to full throttle for 1/2 mile or so and stop, shut off, & read the plug. If you have had no cutting out & the plug is tan or brown, you've got a good mix. If you experience any flat spot or cutting out in the 1/4 to 3/4 part of the band you might raise the needle to the 4th position allowing more fuel to enter the needle jet.
I see that you're in Ohio and if you bought the bike new there, chances are it was produced in the Ohio plant, so all the foregoing may not even be necessary. I'd think the bike would be jetted for the elev. you're at. Probably your best move would be to ride & read first, applying the motto, "don't fix it if it aint broke!"

 

Mine was jetted lean on the pilot and rich on the main. The pilot was a 38,I changed it to a 40 and it made a huge difference, especially when you crank it up for the first time in the morning. It will now idle by itself while I put on my gear. Also my bottom end picked up. I made a few mods to the muffler and airbox and went up to a 158 main and it's still a little rich, but it will scream and has tons of power throughout the band. The 155 main jet turned my header red and the 158 is a little rich. I tried moving the needle to get more gas but it didn't help

 

I too was wondering about the jetting on my EX. It's stock right now, and when riding around at home (700ft elevation) it seems to run real smooth, but when I took it up in the woods today (about 2000ft elevation I think) it would occasionally stumble on the bottom end, and overall felt like it might be a little lacking in power. What does this mean I need to do to my jetting? Any recommendations?