Wondering about the TPS

Searching the archives couldn't answer my question, so, here goes. I have never checked the TPS resistance on my '99 until this evening. The manual says to check the resistance across the blue & black wires. Mine read 5.0k ohms, right where it's supposed to be. The resistance at fully closed throttle is checked with the yellow and black (Y/:) wires and it's supposed to be "650~750" ohms. There's a formula that calculates that value in the book: meter reading of the Y/B resistance x 0.13~0.15 = 650~750 ohms. So, the reading should be 5k ohms. When I first checked it, it read 1.3k ohms. The highest it will adjust to is only 1.6k ohms. At full throttle, it reads about 4.5k ohms.

In the archives, I found a post that reported almost exactly the same meter readings as I got. Has anyone gotten any other TPS readings?

A local mechanic told me that just about every TPS he checks is off enough to affect performance, so I thought I'd check mine. But I don't know how to interpret the results. A new TPS is about $130, so it's not something I'd like to replace if I didn't have to. Thanks.

AS I recall, I got about the same results as you when I tested my '01.

It bothered me a bit until I checked my '00 and my pal's '01 WR and all were about the same. I did adjust my '01 and I think it idled better afterwards.

I didn't realize they were $130. :)

Anybody ever had to replace one?


I DID replace mine. I checked the BRAND NEW TPS.

The reading was the same as MY OLD TPS.

I returned it for a refund.

As I recall, the readings did NOT match the manual.

Ok then, next question. What did you end up setting your TPS angle/reading to? Max resistance reading at closed throttle, or some other value? The closed throttle readings on mine can be adjusted to between about 800 and 1600 ohms. The WOT resistance ends up being about 4.5k ohms no matter what angle I adjust the TPS to.

My TPS variable resistance at WOT was 3.8k and the manual called for 4-6k. I had to rotate the TPS counterclockwise about 1/16 of an inch off the factory mark. It now reads 4.10k at WOT.

My TPS coil resistance was 4.75k and the book calls for 4-6k, so that looked good.

My TPS variable resitance closed is 1.26k and the book called for 0-2k, so that also looked good.

This is for the 02 model.

After checking resistance at a few different positions on both of my bikes I decided to do a little real world testing since, although my readings were very similar, at zero idle (slide all closed) I was getting slightly different readings from my two YZs. I took this to mean there is some room for error here.

There should be a dab of green paint across the TPS and carb body so you can return it to factory position, but I just wanted to see if there was any discerible change to be had. I can't remember which direction, but if you "fool" the CDI into thinking the throttle is more open than it actually is and turn the unit all the way in this direction, in my case anyway, it did not want to idle at all. A slight adjustment over stock in the OTHER direction seemed to give it a smoother idle. I didn't notice any ill effects otherwise so I left it there and haven't gone anywhere near my bike with an ohm meter since. :)

I know the ignition timing is affected by the TPS readings, and assumed it was a continous type of change, but it could be stepped or something, in which case I probably just imagined my idle improving. Not sure...

I had basically the same experience with my WR and YZ.

Bonzai :)

I've had the same experiance that ya'll have. My bike was popping & sputtering. I did all the carb tricks. Nothing. I checked the TPS. Results like yours. When you change the TPS position for WOT resistance you also are changing the output volts as well. When I unplug my TPS the popping and sputtering go away. Not sure if this hurts the bike or not.

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