Does lid removal alter more than the main jet?

[BEAVER.989]

I often see "dump the lid and go up two sizes on the main", etc.

I'm wondering if removing the lid will require adjustments to the pilot and/or needle, as well. I'm thinking the extra airflow wouldn't be realized unless the quad was at speed, which is why it probaly won't have much effect on anything other than the main, but I'm unsure.

I'm having trouble getting my jetting spot on(seems to run rich on the bottom) and thought this could be another avenue to pursue.

[n811]

Well for me it seemed to change every thing. I did eventually put on a bigger carb but the lid was restricting the air getting to the carb. So with it able to suck in air without restrictions the pilot worked better even when at idle. I plugged the tube that pulls air around the gas tank and built my own version of a open lid with a outerwears cover.

[honda400ex2003]

I agree it does change the whole jet picture. it will lean out everything a little bit since it is getting more air easier all the way through. if it is a ton to have to change anything is a different story but for some it makes a difference and some it doesn't. It depends on where you are and what the temps are too. if it is really cold and you take it off you will be very lean since the cold air leans out the motor anyway because it is less dense. if it is really hot out and you feel it bogging from being rich with it on you can take it off to try to get it leaned out. the are is very dense. There are a lot of variables to go through. Honda puts it a bit rich down low from the factory but the main is a bit lean to meet emissions. This makes it have to be jetted with a main only. Just my .02 though, steve

[Muddinguy]

off topic a little.. but does a lot of Mud get in the airbox after pulling the lid ? I'm leaving mine off with the new engine.. but i ride in some muddy conditions once and a while..

[BEAVER.989]

Originally posted by Muddinguy
off topic a little.. but does a lot of Mud get in the airbox after pulling the lid ? I'm leaving mine off with the new engine.. but i ride in some muddy conditions once and a while..

Muddy conditions? ... No, I would've never guessed by your name, lol.

Try an Outerwears airbox cover. It'll keep the mud out... but could still let water in, so be careful with that.

[honda400ex2003]

it lets in alittle bit of sand and dirt. The best thing to get if you want it open is a K&N or an ehs lid. I am amazed at the amount of water my ehs will hold back. I soaked it with the hose when i forgot to take it off and then took it for a ride after washing it and did not have any problem. amazing. If you are careful though you should not have a problem. I rode for over a year with nothing on my airbox and had a bit of sand in it once. steve

[Muddinguy]

Originally posted by BEAVER.989
Muddy conditions? ... No, I would've never guessed by your name, lol.

Try an Outerwears airbox cover. It'll keep the mud out... but could still let water in, so be careful with that.

yea.. Muddinguy was made up in my freshman yr of college.. was just getting into offroading trucks and playing in the mud, was trying to think of a username and roomate said "why now just calling yourself Muddinguy" and it stuck! anyway ill check out on of the outerwears lids..

END HIJACK :D

[MtnEX]

I kinda like the stock 400EX intake and air box design.

The air box is in a stupid place like most, but seals good.... and has safe looking intake snorkel.


I find it really hard to see me running mine without either on a real ride. Too many muddy creek crossings.

I would have trashed my engine twice, just in this month of June.

A mud proof, water proof cover sounds like a great idea.

But if it can flow in more air through the cover than the stock system, how can it keep water out?