Airbox Flapper Mod Questions

I'm thinking about taping down the airbox flapper as many others have, but I have a few questions before I commit to it.

1. Are there any noticeable performance gains? Where in the powerband are these gains? Will it make starting acceleration any smoother?
2. I heard that this makes the bike louder. Does it make the exhaust louder or is it just air intake noise?
3. Will this lean out the bike? I have my bike running just the way I like it. Will I have to increase some settings on my programmer to offset this?
4. Is there any chance that driving in the rain or off-road with the flapper down will damage anything?

IceWolf wrote:

I'm thinking about taping down the airbox flapper as many others have, but I have a few questions before I commit to it.
Before removing the airbox door completely I disconnected that flapper and pulled all the associated crap. I never did anything with the flapper, and honestly I don't think it'll move unless connected. With the big hole in the top side I don't think there's enough suction to pull that flapper up. If it was moving then I couldn't tell.

1. Are there any noticeable performance gains? Where in the powerband are these gains? Will it make starting acceleration any smoother?
Noticeable might be a stretch. I thought this was a sound thing more than anything. I could be wrong.
2. I heard that this makes the bike louder. Does it make the exhaust louder or is it just air intake noise?
Should just be intake noise, and I doubt it's much of an increase.
3. Will this lean out the bike? I have my bike running just the way I like it. Will I have to increase some settings on my programmer to offset this?
Potentially, in whatever rev range it's activated.
4. Is there any chance that driving in the rain or off-road with the flapper down will damage anything?
I don't even use the airbox door. Water has never been an issue, at least on the street where I ride pretty much full time.

I never felt the difference when I did the "flapper mod".

I also now ride with no airbox door. Now THAT makes a difference.

Think about where that flapper door and "snorkel" are. To get water in there you'd have to be almost completely under water. Like, balls deep.

When I did flapper mod I did not have an efi programmer, so if you already have one you're fine without making any adjustments.

You have a powercore exhaust - loud from the flapper mod isn't going to be noticed....


Bottom line from my point of view, go ahead and do it, and never think twice about any negative impact it might have. I'd say about 98%, if not more, of all wr250r/x owners have done it and I've never seen one post about it causing any harm or damage to anything.

Well now I'm thinking I should remove the airbox door then. I looked all over the interwebs and couldn't find much information on removing the door. I was planning on following this guide to glue down the flapper: http://www.wrrdualsport.com/tech-guide/air-intake/68-flapperrem

And then following this guide to remove the AIS system: http://www.wrrdualsport.com/tech-guide/air-intake/72-aisrem

Could anyone point me to an airbox door removal tutorial or tell me how to deviate from the above guides in order to remove the airbox door like Motokid has done?

1) remove side panel

2) remove screw

3) remove two hinge pins (c clips prevent hinge pins from falling out)

4) airbox door falls off into hands

That simple.

If you're riding on street most f time this is great mod.

If you're riding in dirty dusty sandy conditions.....might want to re-think it.

Well I was planning on doing quite a bit of dirt trail riding this summer...sigh. If I just glue the flapper down, is this process reversible? You're not breaking anything off, right? I'd imagine it would just be a matter of finding a solvent for the glue and reconnecting the solenoid.

You can take the door on and off. Just be careful with those tiny e-clips as you pull them off so you don't loose them.

gatorfan wrote:

You can take the door on and off. Just be careful with those tiny e-clips as you pull them off so you don't loose them.

I was actually talking about gluing down the flapper and leaving the airbox door in place. Is this reversible as well?

IceWolf wrote:

Well I was planning on doing quite a bit of dirt trail riding this summer...sigh. If I just glue the flapper down, is this process reversible? You're not breaking anything off, right? I'd imagine it would just be a matter of finding a solvent for the glue and reconnecting the solenoid.

Use a small self-tapping screw instead of glue.

motokid wrote:

IceWolf wrote:

Well I was planning on doing quite a bit of dirt trail riding this summer...sigh. If I just glue the flapper down, is this process reversible? You're not breaking anything off, right? I'd imagine it would just be a matter of finding a solvent for the glue and reconnecting the solenoid.

Use a small self-tapping screw instead of glue.

Good idea. That would be a lot easier to remove than heat-resistant glue.

Still thinking about removing the airbox door though. Does anyone have any experience driving off-road regularly with the airbox door completely removed? I ride street over 90% of the time since there aren't any trails around my area, but sometimes I'll make the trip and ride on some dirt. I'm just worried about the air filter getting too dirty.

IceWolf wrote:

Still thinking about removing the airbox door though. Does anyone have any experience driving off-road regularly with the airbox door completely removed?

I don't. But certainly it boils down to the odds of getting water in there so it depends where you're riding.

gatorfan wrote:

IceWolf wrote:

Still thinking about removing the airbox door though. Does anyone have any experience driving off-road regularly with the airbox door completely removed?

I don't. But certainly it boils down to the odds of getting water in there so it depends where you're riding.

Not just water - dust/sand/dirt.

motokid wrote:

1) remove side panel

2) remove screw

3) remove two hinge pins (c clips prevent hinge pins from falling out)

4) airbox door falls off into hands

That simple.

Is it safe to ride the bike after doing these four steps without removing the AIS components? In other words, is it safe to open the side panel, unplug the tube from the solenoid, take out the airbox door and solenoid as one unit, put the side panel back on, and do a test run? Am I missing any steps? It seems TOO simple.

The AIS has nothing to do with air box mods, you can leave it alone if you want.

IMO taking the airbox door off makes the airbox just like a gasgas or ktm airbox (they have no door you take the side pannel off and the filters exposed) they work fine unless you go in deep water. The amount of dust/dirt that gets on the filter will be unchanged, if you go on a dusty ride you need to clean the filter after every ride with a stock or modded airbox.

I cut a 2 1/2 by 2 1/2 hole above the air filter for max air flow while keeping the opening up as high as possible since I ride off road in wet conditions alot.
This mods not for everyone tho, you cant undo it without making the top of the airbox ulgy.

Forget the flapper. You can pull the stuff that operates it though. It's not worth messing with in my opinion.

Give the door removal a try. If you don't like it it's completely reversible. Don't forget to adjust that programmer.

Thanks Biglake. Very insightful. I do have one more question for you since you seem pretty knowledgeable. I'm leaning towards removing the AIS components, the solenoid connected to the top of airbox door, and the cables that are connected to it, and removing the airbox door. It's my understanding that if I do this and need to put the airbox door back in place, the flapper will be stuck in the closed position unless I glue it open because the solenoid is what makes the airbox flapper move up and down. Correct?

The flapper will flop around in the breeze. There's no spring to hold it shut. It'll just lay there so long as the bike is upright. There isn't enough suction, with the door on or off, to suck it shut so long as you remove the actuator.

Leaving the AIS on after removal of stock exhaust might result in unwanted backfiring.

pbnut wrote:

The flapper will flop around in the breeze. There's no spring to hold it shut. It'll just lay there so long as the bike is upright.

Interesting. If that's the case, wouldn't that cause sporadic throttle response or some other undesired behavior?

pbnut wrote:

There isn't enough suction, with the door on or off, to suck it shut so long as you remove the actuator.

If there isn't enough suction there, it's not restricting air flow enough to matter.

pbnut wrote:

pbnut wrote:

There isn't enough suction, with the door on or off, to suck it shut so long as you remove the actuator.

If there isn't enough suction there, it's not restricting air flow enough to matter.

So if everything connected to the airbox door is removed, the flapper will remain open even if I don't glue it down? Then what's the point of people gluing theirs down? I'm completely lost here. I feel like I need someone to explain it to me as if I'm 10 years old at this point.

I guess ultimately what I want to know is: What's the difference between gluing the flapper down and not gluing it down when nothing is connected to the airbox door? Is there any difference?

If you dont glue or screw the flapper down after you unhook the actuator from it, it will bounce around, this may make a anoying noise, I dont know if it actually makes any noise as I went from stock to gutted flapper and an extra hole above the fliter.

It takes 10 seconds to drive a screw into the flapper to hold it down just do it and be done with it lol.

With the airbox door off you dont need any other openings in the airbox that hole is more than big enough, you would never be able to tell if the flapper was opened or closed with the door off.

Biglake wrote:

If you dont glue or screw the flapper down after you unhook the actuator from it, it will bounce around, this may make a anoying noise, I dont know if it actually makes any noise as I went from stock to gutted flapper and an extra hole above the fliter.

It takes 10 seconds to drive a screw into the flapper to hold it down just do it and be done with it lol.

With the airbox door off you dont need any other openings in the airbox that hole is more than big enough, you would never be able to tell if the flapper was opened or closed with the door off.

+1

Biglake wrote:

you would never be able to tell if the flapper was opened or closed with the door off.

But isn't the flapper a part of the airbox door? So if I remove the airbox door, then the flapper wouldn't even be on the bike. Unless I'm thinking the airbox door is something else. I was led to believe that the airbox door was the device with the flapper inside of it underneath the seat. Isn't the airbox door the thing that was removed in the picture below?

IceWolf wrote:

Biglake wrote:

you would never be able to tell if the flapper was opened or closed with the door off.

But isn't the flapper a part of the airbox door? So if I remove the airbox door, then the flapper wouldn't even be on the bike. Unless I'm thinking the airbox door is something else. I was led to believe that the airbox door was the device with the flapper inside of it underneath the seat. Isn't the airbox door the thing that was removed in the picture below?

The airbox door is on the RH side of the bike under the side panel.

In your photo the top of the airbox has been removed. Some folks don't like to do that since it may make it easier to ingest water but I had a DR650 that I ran for many many miles and creek crossings like that and it was just fine... even with a couple of underwater immersions. Granted I killed the bike before the motor could suck the water in but once I dragged it to the other side I just drained the airbox and was running again.