Any advice welcome!

Just took the airbox lid off my girlfriend's 400ex and rejetted with a Dynojet kit. Bike runs better but I am concerned about the amount of water and mud that might get kicked into the airbox from the rear tires. What is the solution?

I was thinking about putting the airbox lid back on and then cutting a 2" hole directly in the back of the airbox and running some tubing up towards the rear grab bar - kind of like the 4X4 mudboggers do with their quads. Think it will work? Think it will still be too restrictive?

How much improvement from going from the stock filter to a K&N filter & Outerwear?

What about the airbox covers that let the air pass through but are supposed to stop water? Does it work?

Thanks in advance for any and all the help.

 

I have heared good about the k&n air filters, becuase, everyone has them and likes them, i really dont know about the air box thing, there is actually a air box lid that lets air in but not water, where you get it, i bet it has a lot of restriction to do that!!

 

I have the exact same concern. I talked to the dynojet tech and he said the with the stage two set-up you have to run it with the lid off to get fuel ratio right. I tried porting the lid of mine, but it just wasn't enough air. I have a k&n with and outerwears and plan on getting an outerwears airbox cover (found in a magazine last night; I don't really know how good this is going to work). The outerwears is water repellant(not proof), so some water might get in there. But I think with two levels of protection it will be better protected. Also this should solve the dirt and mud issue. The only problem is that outwears cuts down on the air flow a little bit. So two layers may be too much. Th k&n is definitely worth the money. Much easier to clean and maintain. It also gives a significant increase in horsepower and responsiveness. For about $10 extra the outerwears is a good idea(exp. if your going to run with the lid off). It will also keep your filter cleaner and make it last longer. Hope this helps. CJ

 

Thanks for the info. Here is what I have done so far:

1) I reinstalled the air snorkle tube thing. I originally took it off so I could buy a plug from Nac's. The reason I decided to keep the air snorkle in place is due to item #2.

2) I cut the airbox lid with a tablesaw just in front of the middle clips (this makes a really nice clean cut). I installed just this back portion. I think with half the lid missing plus the air snorkle tube being open, It should get enough air. Let's face it, how much air volume can a 400ex flow anyhow?

3) I wedged a strip of 10X4" foam between the seat and the remaining piece of the airbox lid. This stops the mud and water from getting kicked in from the rear tires. Somebody could market a lid setup like this. It would be a stubby lid with the foam already glued down to it.

Went riding today and it seemed to work fine. I need to check the spark plug though. I purposely put a new plug in so I could check it.

Others might think about this setup.

Thanks for the info on the K&N air filter and the Outerwear. I will probably head this route if it is easier to clean than the stock setup.