The fuel screw will affect the air/fuel ratio of the pilot and the pilot affects fuel flow from idle up. The needle clip position affects the flow of fuel at around mid throttle up. The main affects flow from around 3/4 and up.

 

Okay, but do i really need to do all that if my bike seems to be running fine now? I did however notice that it seems to be a bit boggy when you first pin the throttle then it has loads of power ounce the rpms build. Could that be bc i need to move the clip on the needle like you said, and adjust the fuel mixture screw?

 

Unless you ride at full throttle all the time....yes.

Lean = excess heat. And that's a problem you'll have to deal with anyway when it comes to the 400ex.

I've never had much luck with chop tests which is what people tell you to do (run it and look at the plug). I prefer the seat of the pants approach. The advice I gave you on the fuel screw and needle is what I read on numerous sites when I was in your shoes, and it makes sense if you stop and think about it. The main jet will be trial and error. Start rich, work your way down. But hey! Easier then my kids quad, I wasn't sure where to start on it. Too many mods! I tried at least 7-9 combinations before getting it right. What a pain! But it's worth it.

With the right tools, you can remove the main without removing the carb. Run your gas out and remove the bolt from the bottom of the carb. Good luck!

 

Thanks for the info, i will try that tomorrow. Also do i have to remove the carb to adjust the clip on the jet needle. Hopefully i can do it with it on the bike. Thanks for the heads up about taking the main out, but i figured that out already the hard way. First time i took the carb off, but then i realized i didnt have to take it off the bike. Live and learn. Thanks man.

 

Yes, unfortunately you'll have to remove the carb for the needle. I know it''s a pain. [img]i/expressions/face-icon-small-sad.gif[/img] Don't forget to adjust that screw while you have it off. It's tuff to get to later!

 

Thanks again, and not that i doubt you, but do you think this is what i really need to do?

 

Yes, I do. You are flowing more air through at idle and mid-throttle, why wouldn't you increase the fuel there too?

Also a good test that does work...if you are rich. Turn you gas off and pin it in any gear. If it picks up (runs better) while running out of gas, your are too rich. Go down on the main.

It works!

 

Okay, i am going to adjust the clip like you said as well as the fuel mixture screw. Just a question. Where is the fuel mixture screw, and is it really hard to get the needle out? i have a clymer manual and it dosent look all that hard, i just want to know from someone who has done it b4.

 

Mixture screw is on the bottom of the carb. The needle is easy to remove.

 

So all i need to do is take the needle out and lower the clip one position down (toward the point) right? And then turn the mixture screw out 1/2 a turn. Only reason i am asking is bc i want to make sure i move the clip the right way. The needle is flat on one end and pointed on the other right? And if so then i dont think i can mess that up. Now the mixture screw, there are several screws on the bottom of the carb, i looked in the clymer manual and i didnt see anthing called the mixture screw. Is it possible that the manual is calling it the piolt screw? Thanks again for your input and your patients.