Working on the ex

[Riderr4]

Hey All... I got this 400ex a while ago and ive been working on it in between everything. I was trying to get the jetting dialed in but I could never get it to run just perfect. I found out my header was cracked...

http://i1172.photobucket.com/albums/r567/riderr4/IMG_0170-1.jpg

So... I had a friend weld it up for me.
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0172.jpg

Then I decided to wrap it. I used the hit-temp silicone paint and black 2" dei exhaust wrap.
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0175.jpg

Mounted
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0176.jpg

In an attempt to keep the heat down, I fitted a small transmission cooler behind the front frame rails. Its plumbed in-line with the factory system for now, but im thinking about re-doing it like the four stroke tech kit and adding some better mounts.
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0164.jpg
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0165.jpg
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0173.jpg

So after new crush rings and a fresh plug, I got to work on the jetting again... The previous owner cut the baffle out so it flows a little better and i ground down the header welds. Right now thats the only mods and im using a 40 pilot with a 152 main fuel screw 3 1/4 turns out and I tested the plug at idle-1/8 throttle, 3/4 throttle, and wot. All 3 tested very very close to this color, tell me what you guys think...
http://i1172.photobucket.com/albums/r567/riderr4/IMG_0184.jpg

[Drfat400ex]

Well from what I can see, it looks a tad bit lean. But you really can't tell that well unless you chop it. I find the best method for it is to go to a really high sized jet and rev at WOT for a few seconds with each jet until the stumbling stops. Really easy to do and you don't have to waste plugs. Just my opinion. Other than that it's pretty cool, I like the extra cooler!

[Riderr4]

Thanks man. I saw that u run the yfz shocks. I'm supposed to be getting some for cheap next week so that will be next. Any tips on how to set them up as far as pre-load compression and rebound?

[Drfat400ex]

Originally posted by Riderr4
Thanks man. I saw that u run the yfz shocks. I'm supposed to be getting some for cheap next week so that will be next. Any tips on how to set them up as far as pre-load compression and rebound? Hmm I'll have to think on this one for a bit, my rebound is set at fairly fast, pre-load is set high, and compression is set in the middle. I think that's what I'm at and it's a pretty good setup for fast trails/small jumps. I pretty much ride XC but don't actually race.

[Stickman400]

Pic is fuzzy bit that looks about right, maybe a bit rich to me. The threads look rich, but the insulator and grounding strap look about right. Cardboard brown. Might want to wait for another pro to chime in though, I'm no expert on jetting......yet. I'd also recommend putting some kind of guard in front of that cooler before it catches a rock or stick and ruins it. Looks good though man.

[JOHNDOE83]

You cant just pull the plug out and get a jet reading.

If it doesnt pop or back fire, you pilot jet is set accordingly, If in mid acceleration you get a bog or sputter then the needle would need to be adjusted.

Its rare to have to adjust the needle on a 400ex but it does happen sometimes.

For the main jet there is 2 ways to get it dialed in, theres the extensive "Plug Chop" were you make high speed runs and kill the motor. " BUT YOU HAVE TO ACTUALLY CUT THE PLUG OPEN TO SEE MAIN JETT " Thats why its caled a plug chop.

The other way is reccomended by www.jetsrus.com and is the easiest way for main jet adjusting.

Use a large size main jet like a 180, if it wont fully rev out and sputters the top end then its to rich, back down in incriments of 5 until it stops sputtering and fully revs out.

When you pull out the plug and look at it the only thing you see is needle and pilot jett you CANNOT see main jet without cutting the plug open.

Like stickman said it looks about right for your pilot jett, you want that one slightly rich for easy starting and no popping or backfiring, your heat may be coming from your main jet or needle.