I rember seeing something on this forum about how the 400ex comes from the factory with the throttle set at about 70% .
Do I have to reset the throttle now that its broken in?
Also whats a good exaust for a stock machine? Should I also jet It?

 

I think you may be talking about the excess slop or play in the throttle cable. When assembling th bike most mechanics don't really tune things to a very fine degree, therefor it's up to the rider to remove the excess play in throttles. That's why you have an adjuster at the lever. Turn the lock ring counter-clockwise to loosen it and then you may adjust out the play by turning the adjuster counter clockwise slightly and checking the play at the lever . It's critical. however, not to adjust to far ..to test, tighten the lock ring, start the engine, and while idling, turn the bars to full lock in both directions to see if RPMS increase. If so, re-adjust the cable slightly to allow a little play. By having excess cable you fail to lift the carb slide fully at full throttle, thereby reducing fuel flow and top speed.

 

I would definitely tale a look at your throttle to see if you are only opening it up 70%. I know my throttle was only opening at about 70% then it got fixed and what a difference it made. The good old' exhaust question. My buddy just got the white brothers R4 and he really likes it. I like the Pro Circuit T4 Also. I am really happy with my muzzy pipe. I would get an exhaust system and an aftermarket air filter and definitely jet it. I can't believe I actually rode it without getting it jetted and getting my pipe and air filter.