I removed it today after I cleaned the filter.
Its louder and faster. But it is bad for it?
I dont plan on rejetting it, is it running lean now? is that going to hurt it in the long run?

I dont often <havnt yet> ride through streams or rivers, but I will ride in the rain. <and maybe mud, if rain is heavy> How easy is it for water to get in there with no lid?

any comments are appreciated. Thanks.

-Matt

 

17000 registered members here. 13 people have read my post. No one has responded.
This is my second question post. Same thing.

Is this forum usefull in the way it is supposed to be? None of the 13 people have an opinion or comment?

 

Honda's come pretty darn lean from the factory.

I'll give you an example of how lean you're running it now, from my personal experience:

Last year I put on an IDS2 supertrapp pipe, along with some motor mods. With the air box on, I dialed it in perfectly with a 162 main jet (stock jet is a 148). After riding half a day or so, I decided to pull the air box off for the fun of it. So I began increasing the main jet, one at a time, in order to over-jet it (i.e., get it to run badly from too rich a mixture). This is a common way to jet correctly - you over-jet it, drop the main jet size down one or two sizes, this is the correct jet.

By the way, I also raised my needle by lowering the needle clip one notch (midrange throttle jetting).

Anyway, I had purchased main jets up to 175 (six sizes bigger than a 162). At 175, I still hadn't over-jetted it yet (I'm sure I was pretty close).

I can't say for sure, but I would guess with airbox off only, you should be running at least a 152, maybe 155 - again, I can't be sure, testing is the only solution (it may very well be higher).

For me personally, I would NEVER do what you are doing - you're running a sizable risk of premature engine wear.

Jetting is so easy to do on the 400ex. Run to the dealer and grab a handful of main jets (150, 152, 155, 158, 160). They're around $3 a piece. Lots cheaper than hundreds of dollars in engine repair!

P.S. I'm running with the airbox on, don't like the huge sucking sound under me.

ogre

 

Me and a couple of guys i know dont use our lids. If you are using a K&N then you should be using an outerwear for extra protection. And take off the drain plug on the bottom of the airbox, that way if any water does get in it will drain out and not stay in there. How is the quad running, check your plug to see you are lean or not. I dont think you see much difference just by taking off the lid. Take the lid off, rejet, and add a slip on and those 3 things will give the 400 more power.

 

YES, IT"S LEAN!!!
My guess is you should go up to about a 165 main.
Rejet and check your plug, go up until it starts to lose power.
As far as the mud and water, if you know any roofers try to find some Cobra rolled ridge vent and cut it to fit over your airbox. It works great for keeping stuff out unless your crossing streams. If you use some filter oil on it it will stop half of the dirt before it ever gets to your filter.