07 WR450 Slight Miss in Top End


5 replies to this topic
  • jpoehls

Posted May 31, 2007 - 07:20 PM

#1

I have a new 07 WR450. When I purchased it, I also purchased FMF Q4 Pipe, AIS Removal Kit, Upgraded Air Filter, and Baja Kit.

The dealer told me they upgraded the jetting and needle for Salt Lake City elevation and the performance mods.

Here is my issue. Bike starts and idles great. Bike accelerates great. I am breaking it in, and trying to keep under 50% throttle for 20 hours (its hard). In the 50% range the bike is perfect. Now the real issue. When I push the bike to higher constant RPM's of around 50 MPH in 5th gear; which I think is in the 50% or slightly higher range, the bike starts to miss out, and you can feel the hesitation in the bike. When I accelerate the bike to say 55 no issues, but as I back off the gas from 55 and want to run in the 50 to 55 range, the bike starts to misfire and hesitate. Also, when I changed the oil after riding the first 3 hours, the oil was greenish (that may mean nada). The front of the header pipe has turned a mahogany reddish shade (probably just normal heating as I may be reaching here?)

Do you think the bike is jetted to rich? Can the dealer adjust it to do this so I will not over-rev it in break-in (that seems far fetched). I do not understand why when I want to run a constant 50 to 55 the bike starts missing and hesitating. As long as I keep in the lower range of RPM, it runs fantastic. Can someone point me in the right direction?...(please!):thumbsup:

  • xrmarty

Posted May 31, 2007 - 10:41 PM

#2

I don't have this problem, but I've read numerous posts about this issue. The common theme seems to be the TPS (throttle positioning system) problems. I highly recommend you do a search on this subject. There is an easy way to fix this issue via adjustment or down right disconnecting the TPS. BTW: the way you discribe it, it sounds like a bookcase TPS problem.

  • Humunn

Posted June 01, 2007 - 04:51 AM

#3

It's not the TPS. I had the same problem. These bikes come from the factory rediculously lean. Run a search. You need to rejet. I ride between 3000 and 7000 feet most of the time. I had the dealer rejet mine to the following specs:
175 main
JYTR-4 needle in pos #4
50 pilot
45 leak
110 air
This was the recommendation from Dirt Bike magazine. I still have a slight tap at around 50 mph but nothing like it was. I can live with that.

You will notice a glow in your header, particularly at night. The leaner the jetting the more it will glow.

Greg

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  • jpoehls

Posted June 01, 2007 - 06:08 AM

#4

Thank you both for your excellent input. This is a great forum with awesome suggestions. I have researched both suggestions as you both stated.:) Here is how I am going to approach:

1) I am going to disconnect my TPS and then go out for a ride. I did not realize the TPS issues that this bike was prone until the research. I must admit, I had a 400 DRZS that I installed a Kehin FCR MX 39 no TPS as Dr. Eddie suggested (jetted and installed myself). TPS disconnected was never noticed or missed. I am hoping the same effect with this bike. If this does the trick, I will go no farther except checking my spark plug to analyze jetting.

2) If I am not happy with the results, I will purchase JD jet kit, Boysen AC Pump, and Zipty mixture screw...dammit, if I take the carb off (or move it), I am going all the way!!!

3) Perhaps a combination of both, but I hope #1 takes care of everything.

I will report back. Again, thank you for pointing me in the right direction. I am confident after reading both responses, the answer lies between the two according to researching the threads. Glad to see I was not alone!!!:thumbsup:

  • jpoehls

Posted June 03, 2007 - 05:00 PM

#5

:) :thumbsup: TPS it was...I am glad to report that disconnecting the grey triangular TPS plug on the front left side of gas tank above cylinder (3 wires - Yellow, Blue, Black) did the trick. It took all of a couple minutes to look it up in the book, then take a small straight edge screw driver to aid with disconnect. I only disconnected and left wire harness plugs hang.

Headed to road and no hesitation or missing anymore in the 50 to 60 PPH range. Bike ran perfect.

So what is the function of TPS anyway? I can't tell it is disconnected. A very simple fix! Do not need to mess with jets thank goodness.

Thank you all for your input.

Jeff:ride: :ride:

  • jams229

Posted June 03, 2007 - 05:44 PM

#6

:) :thumbsup: TPS it was...I am glad to report that disconnecting the grey triangular TPS plug on the front left side of gas tank above cylinder (3 wires - Yellow, Blue, Black) did the trick. It took all of a couple minutes to look it up in the book, then take a small straight edge screw driver to aid with disconnect. I only disconnected and left wire harness plugs hang.

Headed to road and no hesitation or missing anymore in the 50 to 60 PPH range. Bike ran perfect.

So what is the function of TPS anyway? I can't tell it is disconnected. A very simple fix! Do not need to mess with jets thank goodness.

Thank you all for your input.

Jeff:ride: :ride:


Jeff brings up the same questions that I have.
I have read several of the threads on the TPS, and I am still
uncertain as to what exactly it does... and, if anyone is aware
of any ill-effects of disconnecting it. I understand it is noticeable
on the street, but what will I notice off road?
Thanks.




 
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