After a week in the making, I've finally got it back together and broke in. I had it bored out (.080) and I put a 87mm je piston (10.5:1) in it. I also picked up a supertrapp ids 2 and a K&N filter to go with it. The ids 2 is fairly loud - I did drop the disks down to 7 and that seemed to help a bit. Right now I'm running a 165 main with the airbox lid on. I did crack the airbox lid open on one end (front clips under lid) but even with a 175 main in it I couldn't make it go rich; so I'll pick up some fatter mains soon and dial it in then.

Results: lots more torque on the bottom end, first and second gear wheelies are a breeze. It still seems about the same after that - third gear wheelies still need a tug of the handlebars, but its not quite as hard to do. From what I can tell, the most performance gain seems to be in the midrange. At the local sandpit, there's some pretty long/semi-steep hills (sand consistancy); where before, I would need a run at it and the speed/rpms would stay the same as long as I stayed on the throttle - you know, you certainly couldn't dream of twisting the throttle more and expect more acceleration going up the hill. Now, I really don't need a run at it, and the coolest part, as I assend I can give it more gas and the thing actually accelerates, sometimes to the point that the front end hardly stays down. That certainly put a smile on my face! Top end is close to the same as before - although it doesn't sign off quite as early; before, 3/4 to wot gave an increase in speed, but I really couldn't "feel" it, now when I blip the throttle from 3/4 to wot I can still feel it accelerate. I ran it with 92 octane gas for the first three tanks, then I got 91 octane for it (I was at a station that only had that), after half a tank of 91, I noticed a very slight bit of predetonation, so now I'm back at 92 and everything's good.
Overall, I'm quite pleased with the results; I can't really say that its a "totally different quad" like lots of people tend to say after a mod or two, but it definately packs quite a bit more punch in the midrange. I still, however, can't seem to reach the rev limiter in 5th (185 lbs); I imagine a aftermarket cam would do the trick - but I don't really want to trade my bottom end in to hear the engine skip at wot.

I would like to thank the folks at powroll for all the great advice. I spent a couple of hours on the phone with them hammering out what I was looking for in my 400ex. Best of all, I didn't feel like I was pressured into buying anything from them. Because of this, I wanted to give my business to them. When they didn't have the je piston in stock, they told me to call je pistons direct and order from them. I'm definitely heading back to powroll when I feel the need to do a little more soupin'.

ogre

 

The cam would be money well spent. What do you mean by trade in your bottom end? You don't even have to give them your cam, it will just cost more. If you don't want it to kick back on you at WOT buy a White Bros. rev unlimiter and that should solve that. Otherwise go to larger front sprocket. Personally I hardly ever hit my top end(woods riding).

 

By trading in my bottom end I just meant that there appears to be a trade off between either low end torque or top end power. Stock cam = more low end grunt, less top end power; aftermarket cam (i.e. white brothers, etc.) = more top end power, but less low end grunt. I realize that I could get an aftermarket rev limiter to go with the aftermarket cam - but I would still loss some of my bottom end.

Would a counter sprocket change out with a hotter cam be a viable solution? I mean, would I see a performance gain throughout the powerband? Poweroll mentioned that with a hotter cam, under 1/2 throttle opperation feels kinda like your jetting is off. I spend too much time under 1/2 throttle to have a blubbering machine to deal with.

ogre

 

I have the white brothers all aruond cam and have a very good bottom and decent top. But I use mine for cross country. Yes the countersprocket will help you even it out even with a hot cam. But with the wild cam comes more often valve adjustments. My valves have not needed adjusting in 10 months.