Air Box Mod, and Idle hesitation

Hi everyone. I've reinstalled the airbox components on my 2008 WR250R in an attempt to fix the off idle hesitation that it has. It will hesitate if I grab a whole hand full of throttle as fast as I can from a dead idle. It has 2000 miles on it, a K&N air filter, and a 12T front sprocket. Any ideas about fixing this off idle hesitation? Oh, does anyone have any hi-res pictures under the seat without the airbox mod? I'm not 100% sure I got it reinstalled right. Is the flap supposed to rest in the up or down position? Thanks for any help! :p

yeah mine does this too. i have the fmf programmer.. top of air box removed ...q4 fmf pipe....ais removed.. and it does this....i think too much air and not enought fuel at idle...i may put my lid back on and try different things .....sometime not very often when taking off from stop light or stop sign my bike will die.

Yeah, very annoying. I've had mine stall at a stoplight now and then too. When I goose it like I am, I'm trying to wheelie in 1st gear at slow speeds. Maybe what I'm doing is abnormal and I'm expecting too much?

Mine went away when I did the mods, mostly all at once, not sure what cured it, I thought the programmer would have cured it. Turboedmsp, you sure you have your programmer set right? I am using a PCIII, so can't help you. I still have the on/off jerk at low rpms, but have not heard of anyone really cureing that.

Willcp00, I assume your running stock exhaust, I think you are right putting the flapper back, I only hear bad things on this forum from guys that did the flapper mod with the stock exhaust.

Not sure what fixed the hesitation, I assume the programmer, maybe the slip on (Q4). I saw in one of the mags, (motorcyclist?) they had a long term test bike, switched from an FMF pipe to Yoshi pipe, said it cured the off idle hesitation. He was not using a programmer though. Guess the Yoshi works better with the stock EFI.

thanks for the link mr beat! Very good reading there. Since I don't have an FMF Programmer, I think I'll try putting the stock air filter back on, and recheck for any vacuum leaks.

Does anyone have a picture of the installed air flap solenoid and related parts? Is the flap supposed to rest in the open position? I cranked the bike with the seat off, and the flap never moved no matter where the throttle was, making me wonder if I installed everything correctly. Thanks again for everyone's help!

from what I heard, its only closed when at or near idle. The bike has that hesitation as stock, I don't think the stock air filter is going to help. Find that thread with the flapper mod write up, go through backwards, make sure you didn't miss anything. Good luck.

Since I don't have an FMF Programmer,

There's the problem, you dont have enough fuel or "accelerator pump" to compensate for the massive air coming in.........too lean, flat spot, hesitation......etc.......

i must have a leak too somewhere then. i will check my vacuum cap for the FI when i get home.

Can someone tell me what needs to be plugged up when removing the AIS? I remember caping off the exhaust and the air box but nothing else. I know my ais exhaust plate is leaking but did not think this would cause any harm since it is the exhaust side. I just ordered a block off plate from ebay and it comes with aluminum block off plate plus two vacuum caps. i big for airbox and a small one.....i don't remember what this small cap would be for when removing the AIS. I know you have to cap off a small one for the programmer install but not the AIS...maybe i missed something.

thanks,

OK, so the air box flap doesn't move on mine at any rpm level. Does that mean it's not working? I'd like to get it working to see if this fixes my hesitation problem before I do anything else like buy a Programmer. Any ideas what I didn't hook up correctly? I really appreciate everyone's input!! :p

I know you have to cap off a small one for the programmer install but not the AIS...maybe i missed something.

There is nothing to cap off when you install a programmer.

The AIS removal requires you to cap off the outlet at the head with the plate and to cap off the airbox with the 1/2" cap. Everything in between gets removed. Leave the electrical plug hanging and remove the AIS solenoid and all hoses and pipes. End of story.

The flapper mod removes everything under the seat connected to the flapper. The diaphram on top of the airbox, the solenoid, the vacuum accumulator tank and all the hoses. Again, you leave the electrical plug hanging since it doesn't throw a code. The only thing you cap off is the vacuum fitting on the throttle body. This can be done with the small vacuum cap, or if you are lazy like me, you leave the hose on the throttle body and plug the hose so you don't have to remove the fuel tank. Either way you get the same results. The flapper is normally in the open (down) position when the engine is not running. Screw it down or glue it down or whatever you want to keep it in the open position after removing the flapper junk.

If you are going to hook the flapper back up, you need to simply reinstall all the junk you took off. Pretty simple job. Remount the vacuum accumulator tank and solenoid. Plug the solenoid back in and reattach the hose and diaphram and hook it back to the flapper. There is also a inline check valve between the throttle body hose and the vacuum accumulator tank (little round canister thing). Make sure the check valve is facing the right way or the system won't work (blue side of check valve towards the throttle body). The check valve should allow flow TOWARDS the throttle body and no flow the other way. In other words, it should allow vacuum from the throttle body to the accumulator tank where it is stored until the solenoid opens and let the vacuum operate the diaphram on top of the flapper which in turn closes the flapper.

You guys need to understand the systems you are messing with before you go and remove all that stuff. The AIS and flapper systems are really simple systems to understand. Get a manual and read up. Ripping off stuff on your bike just because someone else did it doesn't mean it's going to give you the same results. Understand what you are ripping off and how it works and why it was put there to begin with. THEN you can reinstall it later when you have these kind of problems. If you have a stock exhaust system you shouldn't even be messing with any of these mods IMO.

BTW, none of this was directed at you turboedmsp, except my first sentence. I just wanted to put it all together in one post.

Well, I'm still having problems. I went through the diagnostics mode and checked all the valves and solenoids. The air box flap will activate in diagnostics mode. The TPS is reading 16 at idle, and 98 at WOT. I even put the stock air filter back in. It still hesitates if I goose it anywhere from idle to about 1/3rd throttle. The bike is completely in stock form at this point. This is getting pretty annoying! Anyone have any idea why she's still hesitating? Thanks again for all your informative posts!!!

clutch cable adjustment? throttle cable adjustment? bad gas? flat spot on the tps?

The clutch feels good and engages completely before it hits the stop, and the TPS numbers rise smoothly while twisting the throttle in diagnostic mode. What else should I check? Thanks!

I'm only seeing a bit of "bog" on my X and only when cold. Half mile or so and it's gone. Airbox flapper tied down and actuator removed with hose capped, Powercore / Powerbomb and FI Programmer with its out of the box settings. If anything I'm thinking my machine is running a bit rich overall. Hmmm I wonder if the earlier potentiometer trick would help? It would richen the mixture in case it was lean at least.

I have also noticed the cold hesitation. All I have is the q4

There is nothing to cap off when you install a programmer.

The AIS removal requires you to cap off the outlet at the head with the plate and to cap off the airbox with the 1/2" cap. Everything in between gets removed. Leave the electrical plug hanging and remove the AIS solenoid and all hoses and pipes. End of story.

The flapper mod removes everything under the seat connected to the flapper. The diaphram on top of the airbox, the solenoid, the vacuum accumulator tank and all the hoses. Again, you leave the electrical plug hanging since it doesn't throw a code. The only thing you cap off is the vacuum fitting on the throttle body. This can be done with the small vacuum cap, or if you are lazy like me, you leave the hose on the throttle body and plug the hose so you don't have to remove the fuel tank. Either way you get the same results. The flapper is normally in the open (down) position when the engine is not running. Screw it down or glue it down or whatever you want to keep it in the open position after removing the flapper junk.

If you are going to hook the flapper back up, you need to simply reinstall all the junk you took off. Pretty simple job. Remount the vacuum accumulator tank and solenoid. Plug the solenoid back in and reattach the hose and diaphram and hook it back to the flapper. There is also a inline check valve between the throttle body hose and the vacuum accumulator tank (little round canister thing). Make sure the check valve is facing the right way or the system won't work (blue side of check valve towards the throttle body). The check valve should allow flow TOWARDS the throttle body and no flow the other way. In other words, it should allow vacuum from the throttle body to the accumulator tank where it is stored until the solenoid opens and let the vacuum operate the diaphram on top of the flapper which in turn closes the flapper.

You guys need to understand the systems you are messing with before you go and remove all that stuff. The AIS and flapper systems are really simple systems to understand. Get a manual and read up. Ripping off stuff on your bike just because someone else did it doesn't mean it's going to give you the same results. Understand what you are ripping off and how it works and why it was put there to begin with. THEN you can reinstall it later when you have these kind of problems. If you have a stock exhaust system you shouldn't even be messing with any of these mods IMO.

BTW, none of this was directed at you turboedmsp, except my first sentence. I just wanted to put it all together in one post.

thanks i know what you meant.. for some reason i was thinking that i plugged something when i installed the programmer....but i removed all this stuff at once if i remember correctly and just runs altogether now. I will still check my throttle body vacuum cap. thanks,

I have the stock can, removed the AIS and did the flapper mod, removed all the vacuum crap under the seat. So far I don't have that problem, so removing that flapper assembly isn't affecting my bike any. I do know that some guys seem to have that vacuum cap on the TB start to move up on them and it has caused a leak with that hesitation becoming quite apparent. I didn't use a rubber plug on mine (simply because I found out I didn't have one that was small enuf) so I ended up using the plastic tit off the end of one of my smaller bungee cords. It was a tight fit getting it on there, but that sucker hasn't moved an iota and to this day it's capped and not leaking.

Update: I called the dealer I bought it from this morning. He said it sounds like a fuel starvation problem to him, and he's going to call Yamaha to see if they will warranty a remapping of the fuel curve.

Remapping? Maybe they'll give you the programmer too...I don't think they can remap it without having a power programmer in there.:p

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