Low rpm stalling problem after installing new pipe

I bought a new 2012 WR450 2 weeks ago. I've ridden street bikes for the last 30 years but this is the first dirt bike that I've owned so I must confess that I don't know much about them. The first weekend I rode it stock and found it to be a complete dog. I then removed the throttle stop and installed a FMF Powercore 4 pipe and now it has all the power a new dirt rider like me needs.

However, I now have 3 new problems:

1) It is hard to start. It usually takes several attempts to start whether the bike is cold or hot.

2) It won't idle for very long without dying. I have to keep my hand on the throttle to keep the engine running.

3) It frequently stalls when I'm riding it when the rpm drops close to idle speed even when the engine isn't under any load (like slowing for a stop or into a tight corner). It is quite inconvenient to be decelerating into a switchback and have the engine stall causing the back tire to skid.

The dealer told me that the WR450 is tested with this muffler so my assumption was that I would not have to have the fuel injection remapped. True? Not true?? Until I get much more experience on the bike, I won't need a higher performance mapping. I bought the bike for trail and desert riding (I won't be using it on the track) so I need it to run well at lower rpm. That's way more important to me than additional power at the top end.

Thank you for sharing your experience with me.

In this case, your dealer is telling you the truth!!! Everyone with the new EFI'd WR's is having performance/starting issues. Getting the EFI re-mapped solves the performance issues. And breaking in the tight engine with a few hours usually lessens the starting issues.

Ypou need to get the comp ECU....it will not run properly with the stock ECU...especially with the GYT-R pipe installed.

Your dealer is right, but not telling you the whole story, for some reason.

You can't change anything on the stock bike without a re-map.

You should put on the full GYT system and get the mapping tool, and all your problems will be gone.

Your dealer is right, but not telling you the whole story, for some reason.

You can't change anything on the stock bike without a re-map.

You should put on the full GYT system and get the mapping tool, and all your problems will be gone.

Thanks, guys! Krannie, what does the "full GYT system" consist of?

Edited by Randwulf

I bought a new 2012 WR450 2 weeks ago. I've ridden street bikes for the last 30 years but this is the first dirt bike that I've owned so I must confess that I don't know much about them. The first weekend I rode it stock and found it to be a complete dog. I then removed the throttle stop and installed a FMF Powercore 4 pipe and now it has all the power a new dirt rider like me needs.

However, I now have 3 new problems:

1) It is hard to start. It usually takes several attempts to start whether the bike is cold or hot.

2) It won't idle for very long without dying. I have to keep my hand on the throttle to keep the engine running.

3) It frequently stalls when I'm riding it when the rpm drops close to idle speed even when the engine isn't under any load (like slowing for a stop or into a tight corner). It is quite inconvenient to be decelerating into a switchback and have the engine stall causing the back tire to skid.

The dealer told me that the WR450 is tested with this muffler so my assumption was that I would not have to have the fuel injection remapped. True? Not true?? Until I get much more experience on the bike, I won't need a higher performance mapping. I bought the bike for trail and desert riding (I won't be using it on the track) so I need it to run well at lower rpm. That's way more important to me than additional power at the top end.

Thank you for sharing your experience with me.

Yea I had the same issue with mine. As soon as you put the comp ECU on, BAM perfect. Starts great, ides fine. The power tuner is a really nice thing to have also.

I bought a new 2012 WR450 2 weeks ago. I've ridden street bikes for the last 30 years but this is the first dirt bike that I've owned so I must confess that I don't know much about them. The first weekend I rode it stock and found it to be a complete dog. I then removed the throttle stop and installed a FMF Powercore 4 pipe and now it has all the power a new dirt rider like me needs.

However, I now have 3 new problems:

1) It is hard to start. It usually takes several attempts to start whether the bike is cold or hot.

2) It won't idle for very long without dying. I have to keep my hand on the throttle to keep the engine running.

3) It frequently stalls when I'm riding it when the rpm drops close to idle speed even when the engine isn't under any load (like slowing for a stop or into a tight corner). It is quite inconvenient to be decelerating into a switchback and have the engine stall causing the back tire to skid.

The dealer told me that the WR450 is tested with this muffler so my assumption was that I would not have to have the fuel injection remapped. True? Not true?? Until I get much more experience on the bike, I won't need a higher performance mapping. I bought the bike for trail and desert riding (I won't be using it on the track) so I need it to run well at lower rpm. That's way more important to me than additional power at the top end.

Thank you for sharing your experience with me.

Did you ever get your bike to run correctly??

Did you ever get your bike to run correctly??

Yes! I took it back into the dealer a couple of weeks ago; he remapped the stock ECU and made some idle adjustments that addressed the problems that I was having:

1) Hard to start -- Cold it starts the first time every time. Hot I can get it to start on the first attempt most of the time by beginning with the throttle closed and cracking it just a bit after I hit the starter. When it's warm I can often get it to start on first attempt with a similar method but cracking the throttle a little more than when hot. However, it is not uncommon for it to take me 2-3 attempt to get it started when warm. I think I'll get better at this as I learn to adjust the throttle opening to the amount of cooling from hot-->cold.

2) Idling -- Idles fine now whether cold, warm, or hot.

3) Stalling -- Doesn't stall now unless I make a mistake, e.g., decelerate below idle speed with clutch engaged.

I'm pretty confident that it's dialed in right for me now as I put it to a pretty good test last weekend. I rode it for 3 days in the Mojave Desert in a wide variety of conditions from high speed graded dirt roads to crawling up steep rocky goat paths in 1st gear and everything in between. So much power! Open up the throttle and the bike just launches, great for accelerating out of a small wash to catch some air or effortlessly clawing uphill in a sandy creek bed.

Thanks for your advice gentleman!

Yes! I took it back into the dealer a couple of weeks ago; he remapped the stock ECU and made some idle adjustments that addressed the problems that I was having:

1) Hard to start -- Cold it starts the first time every time. Hot I can get it to start on the first attempt most of the time by beginning with the throttle closed and cracking it just a bit after I hit the starter. When it's warm I can often get it to start on first attempt with a similar method but cracking the throttle a little more than when hot. However, it is not uncommon for it to take me 2-3 attempt to get it started when warm. I think I'll get better at this as I learn to adjust the throttle opening to the amount of cooling from hot-->cold.

2) Idling -- Idles fine now whether cold, warm, or hot.

3) Stalling -- Doesn't stall now unless I make a mistake, e.g., decelerate below idle speed with clutch engaged.

I'm pretty confident that it's dialed in right for me now as I put it to a pretty good test last weekend. I rode it for 3 days in the Mojave Desert in a wide variety of conditions from high speed graded dirt roads to crawling up steep rocky goat paths in 1st gear and everything in between. So much power! Open up the throttle and the bike just launches, great for accelerating out of a small wash to catch some air or effortlessly clawing uphill in a sandy creek bed.

Thanks for your advice gentleman!

Glad you bike is running better but you've been mis-informed. The stock ECU cannot be reprogrammed. You'll need the Comp ECU to re-map.

Glad you bike is running better but you've been mis-informed. The stock ECU cannot be reprogrammed. You'll need the Comp ECU to re-map.

The service manager told me they re-programmed the ECU. If he didn't / couldn't do that, what did he do to get it to run right? It's like a night and day difference.

The service manager told me they re-programmed the ECU. If he didn't / couldn't do that, what did he do to get it to run right? It's like a night and day difference.

The only thing he could have done to re-map is install the comp ECU....that's it. Period.

The only thing he could have done to re-map is install the comp ECU....that's it. Period.

Well he didn't charge me and it's running the way I want it too so I suppose I shouldn't complain, but now I'm curious! I'll have to go back in and quiz him in detail to find out exactly what he did.

I'm curious too.  My 2012 is stock except for installing the GTYR FMF exhaust.  Mine idles fine and isn't too hard to start, but it takes forever to not die when going into slow or tight corners.  After about 20-30 minutes, it runs fine until I let it cool down a while.  I was thinking it had to have the new ECU installed before it could be remapped.  I don't have the money for the tuner right now, but I could probably handle the ECU price.  I'm guessing I would have to have the dealer to tune it for me.  Any help or suggestions would be helpful.  Thanks.

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