TPS Problems on 03 WR450

Just purchased a 03 WR450 with about 300 miles on it and thought the stumble in the power band was a jetting issue (Tried all combinations of jetting), then borrowed a 01 YZ426 carburetor, installed it, had same problem. Disconnected the TPS (On the YZ carb.) and the ¼ to ½ throttle, loss of timing when away, plugged it in, came back. The 03 wr450 carb., did the same.

Performed the manuals testing and all voltages were good. It must be a CDI issue, but was wondering if this had happened to anyone else?

Also, does it hurt to run without the Throttle Position Sensor?

Thanks in advance


I have rode my bike with the TPS disconnected, I didn't notice much of a difference. I don't think that it will hurt the bike to ride without the TPS connected. Maybe you need to clean the electrical contacts? Good luck.

Thanks for the feed back, I did look at all the connections, but will need to go back over the wire harness to look for issues, I'm glad to hear there isn't much difference with or with out TPS.

After reading tons of other threads on this issue, it is looking like I will just unplug and ride.

Unplugging the TPS should be in the Jetting troubleshooting guide as it will save some people from the jetting fire drill routine. One benefit from this experience is, I am getting good at removing a WR/YZ carburetor.

Thats what I've been saying, disconnect that POS tps, check out the posts on page one that says "Stutter and surge after JD kit and Zip TY"

On my YZ, I went with a vortex igniton because of the stutter. The stock CDI gets stuck between maps and the voltage to the spark plug drops. There were several settings on the Vortex that got rid of the stutter. My new WR does not have this problem.

The Vortex ignition sounds like the way to go, does this replace your CDI, I am looking at replacing mine.


Tried all combinations of jetting

When rejetting, did you try going to a richer needle (not just change clip position)? On my 03 I first tried just going to richer PJs and this helped quite a bit but did not completely eliminate the stutter. I kept stepping up the PJ until it was obviously too rich but the stutter remained. I finally tried replacing the stock needle (Yamaha #OBDUT) with one a few steps richer (#OBDUQ) and the problem disappeared completely! I then reduced the PJ back to a #48 to clean up the richness at idle. The motor now E-starts easily hot or cold, accelerates smoothly right off idle and runs like the proverbial striped-ass ape.

You might give it a try before replacing the ignition module.............

The 1/4 throttle stutter is not always present and if it is, your riding style may not notice it.

I first worked on jetting. I tried every needle setting and even another leaner needle. The bike stutter acted rich and sent me on a long runaround, although I learned a lot. I believed what Vortex told me about the spark plug voltage dropping, because I had a 250WR act rich when the battery was dischaged with the head lights turned on. (It had a Baja design kit and I did not change out the high wattage stock bulb for the low wattage bulb Baja suggested. So it wasn't a Baja problem.)

The Vortex ignition is a CDI unit that replaces the stock CDI.

The stutter at 1/4 throttle occurs when you try to ride at a constant rpm. I noticed as I got use to the bike the problem is not as pronounced on the stock map because I give it more gas. The YZ seems to want lots of throttle or off, not in between. It was hard to show the dealer this problem because the young guys there ride on and off. When I used a constant throttle, they were surprised at the stutter. After calling Yahama, etc. they said they could not fix it and thats when I looked into either replacing the TPS or going with the Vortex.

I went with the Vortex because it has 10 different maps from traction to performance including the stock map. The traction maps did not have the stutter while a few of the performance maps did. Again, I guess a racer does not sit at 1/4 throttle. It was very enlightening how the CDI can cause one to think they have a jetting hole.

I still wonder why the CDI can't just throw all 12V to the plug all the time rather than varying. I guess it is a software bug when the unit drops the voltage to <1V and causes the stutter.

Where did you buy the Vortex CDI from? Got a link?

I love my WR (YZ exhaust cam) in the trails, It runs excellent, but on the road at a steady 45mph ish it feels like crap. I'm curious jdd123 do the traction maps on the Vortex ignition noticably effect performance compared to the performance maps, is there a big difference?

Yes they did on my YZ450F. The difference between maybe a 2 or 3 wasn't noticible but from like a 2 to 7, yes. The traction settings seem to take longer for the bike to rev up and makes it less jumpy. The performance settings make the bike want to throw out the power all at once. It is good for my YZ giving me some flexibility. However being that it is a 450, it has goobs of power and even the "traction" settings do not make it slow dog. The traction settings got rid of a stutter at constant 1/4 throttle.

To sum it up, I think that a racer or perfectionist will notice the map changes dramatically. A newbie or person who just likes to ride easy, for fun, small 2 ft jumps (i.e. old man like me) will find the map differences not that big a deal. (But then set the map on the highest performance.)

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