is a remap needed with a slip on pipe?

Hello fellow bike enthusiast
I just purchased a brand knew yamaha 2011 wr250x. I figured since it is winter time i would go ahead and start doing modifications before i register the bike for this coming riding season.

I just recieved the slip on exhaust i had ordered from ebay(got a great deal), it is a big gun evo r

Big gun and my local dealer have both advised me that i would need to have the bike remaped. i was not planning on purchasing a fuel controller and im wondering what problems i will run into if i run the bike with the aftermarket slip on and the stock fuel map

the bike has the stock ais system and no mods to the air filter/box
i will be removing the exup when i install the exhaust i am aware that i have to leave motor for exup valve intact unless i add a servo

my main concern is i do not want to do any damage to a brand knew bike by adding exhaust without the remap.

answers are greatly appreciated, thank you

It's not going to "hurt" the bike.
No tune needed but you're not getting the most out of the pipe - I've seen sportbikes run worse with exhausts and no tune.

You're on a standard upgrade path for the WRR.

You won't notice too much with just replacing the pipe. Replace the pipe and open the airbox and you'll notice a lot more.

Opening the airbox, it's easy. Stage 1 is to remove the servo on top of the airbox and glue the inlet flap down to the bottom. (easily undone)
You can either remove the servo hose... or just plug it with a bolt where it attached to the servo.
Note: If you want to remove hoses, you can buy the 'rubber caps' in most auto stores. Couple bucks.

When you add the pipe, get the EXUP servo replacement plug or leave the servo motor connected.
Note that adding the resistor in the plug lets the computer work without displaying an error code, but not properly. I've swapped them out a couple times and noticed a big difference in performance with the servo connected. I finally went ahead and bought the proper servo 'replacement' plug from 12oclock labs, the bike runs much nicer with it.

Then remove the other stuff. (It doesn't really hurt perf, but nice to remove excess poundage anyway).

Then add a fuel programmer... it really lets the bike perform.

Let us know how the pipe performs too. I've added an FMF Q4 on my bike... but it is still way too loud. I need to figure something else out in the exhaust, either quieting the Q4, another pipe, or removing the 'inlet stuff' from the Yamaha pipe.

I was talking with the Yama dealer here in Kelowna. They told me that with just a pipe, no programmer is nessasary. But as mentioned above, it won't make much difference other than sound. If you muck with the air box etc then the bike will be lean and they highly recommend a EFI programmer at that point.

Interesting...I was told the exact opposite from the dealer. Nonetheless, adding the programmer definitely gives the bike a much needed boost.

I think the theory behind it is an exhaust doesn't affect the income air which would make it run lean ??

I dont know if its worse if dont install a programer but its better: check the maps of the powercommander : stock map and with only an aftermarket muffler (leo vince f. ex.): there are great differences between the maps. It seems that the backpressure from the muffler have much to do with the fuelintake

I'm hoping to fit the big gun evo r too, let me know how you get on with the programmer! :)

IAmABug wrote:

I think the theory behind it is an exhaust doesn't affect the income air which would make it run lean ??

I think you're right, but what did you think bike will run lean??? ECU uses few sensors to mix proper AIR/Fuel mixture. See this picture:

intake air pressure is taken as parameter thus will affect FI.

Skrew, the general theory is that Yamaha intentionally tuned the R/X to be slightly lean in stock trim for pollution/emissions reasons.

As the theory progresses, everything one does to influence the flow of air through the motor will push the mixture leaner.

So opening the exhaust will make things a little leaner. Not enough to cause damage to motor.

But - as the flapper then removed/taped down, and a higher air flow air filter is added, or even the airbox door is removed the theory is the little engine that could is now in a dangerously lean condition if an aftermarket fuel programmer is not added.

All this is the general thought process of most, and there's very little actual data to support that notion of where the bike becomes dangerously lean.

Most of us prefer to error on the side of safety and add the fuel programmer long before that line is reached.

I don't think the Yamaha supplied ECU is versatile enough to compensate for modifications beyond the stock settings and stock equipment.

motokid wrote:

Skrew, the general theory is that Yamaha intentionally tuned the R/X to be slightly lean in stock trim for pollution/emissions reasons.

As the theory progresses, everything one does to influence the flow of air through the motor will push the mixture leaner.

My though was that ECU will use AIR pressure sensor data and increase fuel amount, of course to respect factory ECU limits... And this can only affect throttle responce as we just allow engine to breath freely

motokid wrote:

So opening the exhaust will make things a little leaner. Not enough to cause damage to motor.

Not sure... Once again to "breathing": allowing exhaust gasses to leave pipes more freely will free engine from wasting precious energy to clean combustion chanber at 4th stroke. IMHO by opening exhaust we will not (shouldn't) affect lean state of intake mix.

Generally I am thinking of buying lambda-gauge to see what is happening to Air/Fuel ratio in typical conditions with stock and modded setup...