Need jeting help

Honda

I need some help in jeting my 2004 400ex. I just bought a full exhaust big gun system and I need some help on the jeting. The bike is all stock except for a 14 tooth sprocket and the big gun full exhaust i am puting on it. I am not that familiar with jeting. If you guys could help me i would appreciate it.

Thanks

What does Big Gun say?......I think I would call / e-mail them and start there.

Yes, get Big Gun's suggestions and make the changes they state. Once you've done that, you may potentially still want to dial it in better.

There are a lot of good article on jetting basics on the internet. Google can help you. Read up on several so you understand the basics of 3 primary circuits based on throttle position.

I think working the bottom circuit up method is best. Remember when making changes, do them one step at a time. Always start by checking the float bowl to make sure it is at the factory recommended setting. Then adjust the fuel/air screw and based on how many turns out from all the way in it takes to get it running right at idle will determine what changes you need to make to the pilot jet. Then work on the mid-throttle performance with the needle clip adjustments. And up to the peak throttle with the main jet.

Needle last, it's the same as the mixture screw is to the pilot jet. When you up the main you up the middle too so adjusting it before the main jet is a little cart before the horse.

If I were you I'd make an order from RMATV for a 40 pilot, and the mains 150, 152, 155 and 158. The whole order should be like $20 shipped. Start by installing the 40 pilot, 2 turns out on the mixture screw and a 155 main. Should be close with the needle in stock position. What ever you do don't just get one jet at a time, they're cheap and something you should have for tuning anyway.

Dont forget to remove the airbox lid before you jet.You can either get a freer(sp)breathing lid or drill some one inch holes in your stock one. You may have to fine tune afterwards but not likely.

Thanks for correction on the needle, I didn't know that.

ok thanks guys i will let you know how it goes

Dont forget to remove the airbox lid before you jet.You can either get a freer(sp)breathing lid or drill some one inch holes in your stock one. You may have to fine tune afterwards but not likely.

If you're removing the lid that will change my jetting recommendation. What are your plans on that?

i honestly dont know i dont really want to remove the lid. I would probably drill holes in it if anything. I dont really want dirt and stuff being sucked in it though so idk. Do you guys know a good place to buy a airbox lid?

It is unlikely that dirt will fall into your airbox but fine dirt will regardless if the lid is on or not. The only times removing the lid could cause problems for you is swampy or very liquid like mud, or water crossing.

If that isn't part of your typical ride, then take it off. If you drill holes, you can always tape the holes over for mud or water crossing.

Letting in more air will require more fuel but it's worth it. If you don't want to drill out the stock lid, then go to the dealer and get another one. How much can they be......:bonk:

this is what you want. i have one all you have to worry about is water1203551150878080_8.jpg you can find them on ebay

this is what you want. i have one all you have to worry about is water1203551150878080_8.jpg you can find them on ebay

whats the name of it?

oops EHS air box lid

I drilled holes in my sons EX lid and used womens knee-high stockings to cover the holes. It sounds "Cheesy" but it works very well.

I drilled holes in my sons EX lid and used womens knee-high stockings to cover the holes. It sounds "Cheesy" but it works very well.

thats actually sounds like a pretty good idea

What did you deiced on, lid on, custom lid, no lid?

i decided to leave the lid on right now. I got my big gun full exhaust in and on. sounds Awesome! it didnt have any instructions on jeting so i have just left it for now

i decided to leave the lid on right now. I got my big gun full exhaust in and on. sounds Awesome! it didnt have any instructions on jeting so i have just left it for now

You can do some damage if you're running lean so if the power feels good you should still pull the plug to check the color.

Got pick of the pipe mounted up?

i decided to leave the lid on right now. I got my big gun full exhaust in and on. sounds Awesome! it didnt have any instructions on jeting so i have just left it for now

...you will be ok for a few days!!....just dont run it too Hot or too hard for very long.......:bonk:.....

.....with that said.......make damn sure that you re-jet(at least the main) within a few days!!........

..."(you will be ok for a few days!!)"...lol...yeah I know...:bonk:

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