400ex not running right?

[300exBorg]

I got a 2003 400ex that I've been riding for the past year. Everything has been great up until now. I just put a FMF powerbomb on the bike a few weeks ago and ended up breaking the neutral switch the day I put the powerbomb on. So I did not get to ride the quad much with it on besides a few laps and all seemed to be well. Well the quad ended up sitting in the garage for 2 weeks until the neutral switch came in today. I put the new switch in and changed the oil and fired the quad up. I noticed that something was not right when I would really punch on the throttle. The low and mid range power was all there but it's like the bike lost all its top end. It would stop revving before the rev limiter it seems and not go any further. The thing is if I gradually press the throttle and not "punch" it I do have top end power. The bike sounds great I do not hear any weird out of the ordinary noises and it does not smoke one bit. The motor sounds healthy but it's just like it's not all there anymore. I have no clue where to start and any help would be greatly appreciated. Everything that has been done to the bike including jetting is listed in my signature.

[CJM]

Edit nvm.

Make sure you dont have an exhaust leak.

You also seem rich with a 165 main for just an exhaust. Check your plug, report back what color it is.

[300exBorg]

I just noticed I did feel a little air blow out the spot where the header and slip on meet (i mean a tiny bit too). It did not increase at all while I gave it throttle like I thought it would tho. I am going to check the plug tomorrow morning and see what it looks like. I just hope something like my top end didn't go or anything crazy like that since I have never tore one of these quads down. Is that something a failing top end would do? Like I said it does not smoke one bit tho.

[300exBorg]

If I was jetted rich wouldn't the bike have acted up more with the stock header on also? Like I said before, I have been jetted at 42/165 ever since I put my HMF pipe on and it def. did not feel like it does now.

[CJM]

Possibly. But you gotta remember the stock header vs an aftermarket setup cant be much improved upon either way.

[300exBorg]

So pretty much I'll take a look at the plug tomorrow and go from there... I'll report back in the morning once I go to the garage. Thanks for the help

[300exBorg]

Alright, I took the plug out of the bike today and from what I can see it looks black. I know that you're supposed to chop the plug to get an accurate reading but I am not exactly sure how to do that (i will if it's needed though). I am going to attach a picture of the plug below. Let me know if this is good enough or if I should cut the plug up. If I do have to cut it is there anywhere that shows you how to do it?


pic of spark plug...... http://i821.photobucket.com/albums/zz139/borgeyyayo/IMG_20120726_104628.jpg

[CJM]

That looks rich to me. Drop to a 160.

You have your air box lid off? If not take it off before you lower the jet and see what happens.