Throttle position sensor voltage?
 

I couldnt find this section in the FSM. In my saga of getting my bike back to factory specs from the PO, I swapped over his F2 carbs for factory F3 carbs. I had the TPS off in my quest to rip the carbs apart to replace a broken fuel nipple without realizing i didnt need to take the TPS off.

SO, my question is... I think the inside of the sensor might have got turned, and i want to make sure it didnt get turned a 180* or 360* circle, and the sensor read that the carbs are open when they are closed. How should i check the pins for voltage? Like... what should they read when the throttle is at idle, and what should it read at WOT? (I can also test them on the table right... they dont need to be hooked up?)

Thanks alot.

Found it, section 16-11. But... i dont understand a damn thing the manual is saying. I see it requires a special adapter tool to connect the pins, and have bare leads you can test while the connectors are connected... but it has some weird formula. Can anyone tell me just what voltage im lookin for at closed, and wot?!?! lol.

Alright well no one chimed in, so I put my brain to work and figure it out myself. (Best way to learn eh? by experience.) However, the only thing the FSM said about the TPS was if it was OK or not, not whether it was in the right posistion. (for those of you that havent had one apart, there is a sensor that rotates in a circle, with a flat head slot in the center. The flat head part is attatched to the bar that the throttle plates are on... therefore reading the posistion of the throttle.)

To explain this someone who possibly searches for this in the future, I will write out what I learned.

If you have a factory service manual, turn to 16-11.

Turn ignition to ON with the TPS connected to its harness. Puncture the wires with your volt-meter. Put the Negative on the Blue wire, and the Positive on the Yellow w/Red Stripe. Write down the voltage you get at idle/throttle closed. This is your base number; Va.

With the ignition switched to ON, put your Negative on your Blue wire, and your Positive on the Red w/Yellow stripe. Measure your voltage at idle/throttle closed. Write it down.

With the ignition switched to ON, put your Negative on your Blue wire, and your Positive on the Red w/Yellow stripe. Measure your voltage at Wide Open Throttle (WOT). Write it down.

Do this calculation for WOT.
-Va X 0.824 and write down the number

Do this calculation for idle/throttle closed.
-Va X 0.1 and write down the number

Your TPS is within spec if your result of the calculation for the WOT is + or - 10% your baseline Va number for your WOT and idle/throttle closed, respectively.

For example:
My Va was 4.69V.
My Volts were 3.91V at WOT.
My Volts were 0.44V at idle.

WOT calculation: 4.69V X 0.824 = 3.86456V (normal if within + or - 10% of 3.91V)
Idle calculation: 4.69V X 0.1 = 0.469V (normal if within + or - 10% of 0.44V)

WOT was 3.86456V. + or - 10% of 3.91V was 4.301V to 3.519V
Idle was 0.469V. + or - 10% of 0.44V was 0.484V to 0.396V

Therefore, my TPS was in good, working condition.

idodirt, chime in with your extensive library of knowledge!

I know this is an old post but I think it should be noted to anyone trying this test on their own should be aware that idle voltage should be checked with idle speed screw backed all the way out ensuring throttle blades are fully closed. At first I checked it with my idle speed set the way it was which gave me a voltage that my "Va" voltage couldn't come within + or - 10% of and I was all set to get another TPS. It wasn't until I re-read the procedure in the service manual that I spotted my mistake, backed screw all the way out and re-checked voltage and all was within spec that time around. Which is cool because I found a new TPS insn't cheap.

Wow, I feel bad that I missed someone's request for help on something. Maybe a PM might have helped. Oh well, there's good information here anyway.

I actually spotted the post in a Google search and "Intiractive's" example was what I needed because the service manual gave a formula that was in my opinion very vague with no example and had me scratching my head going "huh?" and the above example made sense of it all, it's just that I got lost in the confusion of the manuals procedure that I missed the part about backing the idle speed crew all the way out prior to checking voltage at idle. Carbs are off the bike at the moment and now that I have a factory service manual along with other carb tips I've spotted on this site, the carbs are being cleaned the way I should've cleaned them in the first place when my son first got the bike a few weeks ago. We should have it back together tonight and I'll post how it worked out.

A thorough cleaning of the carbs did the trick, at first glance they seemed pretty clean but it's amazing how just the slightest piece of crud can mess things up. Carbs still need to be synced and idle mixture screws need adjusted but I'll pop the question about the mixture screw adj procedure in another thread.

Well, as you've learned with carburetor cleaning, the devil is in the details. They really have to be spotless (at least internally) to function the way they were designed. Now with 4 bikes, carburetor cleaning is an annual thing. I picked up an ultrasonic cleaner from Harbor Freight. Works great..

The devil is in the details is spot on. I've messed with cars all my life and didn't play with bikes till a few years ago. The fundamentals are the same however I've learned that bikes are FAR more picky in regards to tuning, just a fraction of a turn too many on idle mixture screws can make the diff between the bike running great or fouling a spark plug. 2 strokes are worse even though the design is more basic because every aspect of the engine has to be spot on in order to run well. I have a nephew who has a 3cyl 2 stroke H2750 Kawasaki and tuning is even more critical on it compared to any of his 4 stroke bikes which are picky enough already.