07' WR450F Stutters at constant throttle

Hey hows it going? I have a plated 07 WR450F with a JD jet kit, FMF powercore and grey wire mod that I just bought and had shipped by boat to Maui from Kauai. When I test rode it on Kauai it seemed to run fine but I did not ride it much at all. I got it off the boat and was not able to ride it for a month.

The bike starts up great and idles perfectly, it has plenty of power on acceleration but when it is at a constant throttle position it stutters and bucks like its running out of fuel, it also backfires. It is especially noticeable on the street but off road as well.

I read up on this problem extensivly and have disconnected the TPS and it did nothing. I gave up and brought it to a shop and they rebuilt the carb and also found the spark plug to be VERY black, that was replaced and it is still doing the exact same thing. Any other idea's on what is causing this problem? Bad coil or ECU maybe is what the shop is saying but he seems semi clueless? Thanks so much, I bought this bike for its reliability and have not even got to enjoy it yet :)


Edited by Mendo

When you figure it out let us know.... :)

Latest I found was a possible connection to dielectric grease on the TPS connector. Such a low voltage (<1v ) is easily affected by small amounts of resistance.

OHHH SHIT. Im all over this thread. My 04' WR does the exact same thing!

Either the jetting is incorrect (the needle) or you are detecting the 'WR Stutter', a common issue with WR's and the soultion is pricey (Vortex CDI). Do a search in this forum for write ups from James Dean.

Confirm your jetting is spot on before you try any other solutions.

The Dynatek Programmable DFS7-23P will stop the stutter!

Edited <<< no for sale adds in the open forums >>> Moderator (William1)


Edited by tomerb

I'd like to know more about the Dynatek ignition before spending $300 on one. Is there a good thrread about it curing the TPS issue? I've seen a short thrread about it, but only a handhul of folks said that they had actually bought one. It seems like if it's really the "TPS stutter cure" lots of people would have installed them.

Does it still use the TPS?

I had the TPS hooked up on mine

Edited by tomerb

I wonder why some WR's do it and some don't.

My 08 runs clean from top to bottom.

Mine run clean from bottom to top also if I was on the throttle hard, say going from Zero to 70MPH if was smooth as silk.

Edited by tomerb

my 07 runs great at any holding throttle. my jet is 170 main, 45 pilot, 40 leak, fuel screw is1-1/75.

So turns out it was the JETTING! this drove me insane but we figured it out. Just a FYI for others having this problem

Glad to hear you've got it working properly! I believe that's the primary reason why some people notice the "stutter" and others don't, jetting. With proper jetting, you can just barely notice the stutter at all. Or at least, that's how it's been with me & my riding buddies.

My WR400f had severe stuttering and it also turned out to be jetting, I have leaned it out a lot and it now runs smooth. Just got to install a smaller pilot and it will be perfect.

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