Jetting, Jetting, Jetting

[timewass]

I have a 01' 400Ex with a Pro Circuit T4 slip on and the airbox cover is on. I went to a 160 main and a 42 pilot, clip in stock position (3). It runs pretty good over all, but I have a problem. If I'm climbing a very large hill and have to let off a bit to straighten out or to bring the front end down, then I can't get back into the power. It just wants to bog and die. I'm climbing in second with stock gearing. It just looses all power then I can't get back into it like I'd like to. I just have no power once I let off a bit. Could leaning out the needle help this or is my main too fat?

[gojk]

I would try leaning the main. It also depends on the hill, but I climb some pretty steep hills and in second they aren't any prob.

[timewass]

The steepness of the hills vary, and if I stay at WOT up the hill I'll be fine, but as soon as I let off, it starts boging. I'll drop back to a 158 main and see how that does. Someone also mentioned to me that I may be getting too much gas when I first get back on it . they said that I may need to move my needle clip to position #2.

[400extracc]

have same pipe, t-4 with stock filter and airbox mods. pipe came with a 160 main and a 55 pilot. did not work. went down to a 155 main stock pilot air/fuel screw 1.5 turns from closed, and moved the needle jet clip 1 possision down from stock. haven't had a chance to give her, her all, but some passes around the street seemed to run nice. pull real hard in second.:macho

[timewass]

I moved my needle clip up a notch to position #2. It was running way too lean then. My plug was almost all white. I moved it back then changed my main from a 160 to a 158. I am still getting the same results. I loose all power on long climbs. Other guys I ride with have stock EXs and they are doing better then me on the hills. They have no problem keeping the power up. I've ridden their's as well and I can tell a big difference. Their's has more mid to bottom end than mine does. Theirs just keeps on pulling while mine will die. I also got a 45 pilot. So I'm going to have a 158 main and a 45 pilot. Any suggestiong on the air/fuel screw? It's at 2 turns out right now.

[Doibugu2]

In order to get your bike jetted properly, you need to know which circuit your on when you loose power.

I don't think anyone on this site is using a 45 pilot. The guy that is using the 55 pilot does not know what he has or mistyped the number. No one is definatly that high.

Go to the tech articles on the top and read the jetting info. Then do a search on jetting becuase there are 100's of threads about it. Read info from guys that seem to know what they are doing. Then go and take your carb apart again and fix what you did wrong.

Also do a search on Guy, because he will have similar mods to you and you might be able to copy his jet settings. He was having a few problems a week or so ago.

[timewass]

normally I loose power at WOT , but not normally. Only after the bike starts bogging down. but once it starts bogging, it doesn't matter where the throttle is, it wants to bog. I can pull in the clutch and stop and it will still bog until I rev it enough to clean it out. It makes me think its too rich, but the plug doesn't indicate that.

[Nate]

Maybe you got some dirt in the carb. when you were changing jets around. Also you might try a size 40 pilot jet and see how that works.

[timewass]

I did have some dirt in the carb. Two times within a day I had to take my pilot jet out and clean dit out of it. I completely disassembled the carb and cleaned everything.

[twisted threads]

I think your main jet is to big. Have you tried the hill with your airbox lid off? My buddy just went through the exact same problem. Keep going down in main jet sizes and see what happens. I would put a 155 in there if your air box lid is on.