Bike Sputters During Warmup

I ride a 2011 WR250R. Ever since the day I bought the WRR when I start the bike if it's cold(haven't ridden it in 1-2 hours) it will stutter under acceleration. This is not something that comes and goes, I could set my watch to it... Once the bike has reached close to it's operating temperature(After 5-10 minutes depending on the outside temp) the problem goes away 100% and will not come back until the bike is turned off a left to cool back down for a couple of hours. Even on a warmer day the bike does the same thing, but of course warms up faster...

To elaborate on what I mean by stutter. As I am releasing the clutch to move the bike from a standstill, the bike instead of smoothly accelerating will jerk forward as if it is almost out of fuel... It actually feels exactly the same as trying to accelerate when you are seconds from running out of fuel. Or the feeling you get when trying to ride a carb bike right away without letting it warm up on a cool day...

My first guess is that maybe there is something wrong with my fuel pump. I know that at least the older 08' WRR's had troubles with their fuel pumps failing. However mine is a 2011, and it has never stopped working and after the bike is warm it works flawlessly...

Other than that I am not sure what could be causing this to happen? If anyone has any idea, or has had this happen to them please let me know.

On a side note I bought my bike from a dealer in a town 200miles away from me. So that is why I haven't gone through the trouble of taking it to them when I first realized the problem was happening... The bike now has 5,500km on it and the problem has been there ever since the 1st km...

I had a similar problem with a boggiing out and jerking forward thingy. I did a couple things and now it is gone !
- Clean airbox/ and filter. get a K&N Hi flow filter if you dont have one. if you do then clean it with a K&N cleaning kit.
- Think about getting a FMF Power Programmer. It really livens up the engine and makes it much smoother and wholesome under acceleration.
The FMF power programmer is the best investment of all.
- Open the air box, cut a few holes here and there with a dremmel and it breathes easier.
Well
Good luck!

My 2008 does exactly the same thing. I think it's probably just something to do with the fuel injection system warming up. I mean, are there any other 250cc fuel injected engines out there to compare it to that don't perform well until they are warmed up?

Foofighter, since it appears to be the way the bike has run since new, it would be the most logical thing to assume that maybe there is probably something about the stock fuel mapping being lean for the cold start up period? A possible glitch when they programmed the module for the bike. Only way to tell for sure is if you can get an O2 reading for the air fuel ratio during warm up & transitioning to fully warmed up.

SSWRX - you are probably right. I would love to take an O2 rating, but I don't really know much about all the tech on these bikes or for any engine really. I can change the oil on my WRR, and clean the air filter . . . that's about it and that's enough work for me, as long as it reliably starts and doesn't have any safety issues :)
I wonder if it's all WRs or just some of them?

I think Foofighter's bike may be the first one to have this issue. I don't recall anyone else ever having the same problem with a new WR. I know my bike ran fine since I bought it new in 2009. I've added a Power Commander since then but it ran just fine stock.

sswrx wrote:

I think your bike may be the first one to have this issue. I don't recall anyone else ever having the same problem with their WR. I know my bike ran fine since I bought it new in 2009. I've added a Power Commander since then but it ran just fine stock.

Well, I'm not the only one, cause FooFighter is the one that started this thread. I just noticed that my issue was identical. I guess it's a rare issue.

Sorry Pecalunus, got my posting all botched up. I meant to quote Foofighter's post in my first responses. His bike is the first one I've heard of being brand new that runs bad.

No problem. That's good to know, cause I thought they were all like that, since mine was like that new too, and it's the only WRR that I've ever own, or for that matter, even seen :)

Once I did the airbox mod, removed AIS, swapped the header and exhaust for FMF, and installed a fuel programmer... I was able to pretty much get rid of this problem through programming. However I sometimes feel it sputter a bit in the first few minutes of riding on cold mornings. So maybe I still haven't gotten the programming right, but it is definatly not as bad as it was...

Just an off the wall idea. Did you try a new spark plug? Maybe the current plug has difficulty igniting the fuel mixture when it's cold & rich? I had a plug go bad on me when I had just a little over 1000 miles on my WR to the point where it would not stay running. Could be Yamaha had a bad batch of plugs going into some of these bikes.

I'm sure you put some fresh gas in it right?

I have a 2012 that I bought new a couple of months ago, about 1200 miles, and it does the same thing. The last time I rode it it seemed to start doing it at steady throttle in the low rpm range. It was the coldest day I've ridden the bike (about 40). I'm hoping it's a restricted air filter messing with the fuel injection, but it also feels like it could be the fuel pump.

Alot of the bikes do it. It just needs to warm up, The bikes come lean ffrom the factory. Don't obcess over it.