TPS good, bad, or needs adjustment?

I'm getting these resistance readings from my TPS. The constant resistance (blue and black wire) reads 4.6 ohms. The variable resistance (yellow and black wire) reads .21 Ohms closed throttle and 3.5 Ohms full open throttle. The full open throttle is the only one out according to the manual. I still need to check the input and output voltage but I need to get some smaller probes mine are to big and blunt to get in there, could I use a paper clip or something to poke in the wire harness and then touch the probes to them or would that give me an inaccurate reading?

Here is why I came to think that my TPS may be bad. Since I did a rebuild on my bike it's had an intermittent idle problem. Feels like the throttle is stuck at times, It runs perfect for a while and then it will act up for a while. I let off the gas and it stays at a high RPM like the throttle is stuck partially open. If I pull in the clutch it stays idling very high and won't come down, the only way I can get it down is to let the clutch out a little till the rpms come down and then pull the clutch lever back in. It will stay idling fine then. I originally thought it was just the throttle sticking but I've pretty much ruled that out. Cleaned everything and even while its idling high I can sit there and play with the throttle all I want and it wont idle back down plus I can hear the slide closing. Also if the throttle was stuck open it would idle back up after I got the rpm's down by using the clutch. I've gone around all the places were there could be air leaks with propane and found no changes in RPM, plus it's seems to be more then just a hanging idle from being lean. Usually in that case it will slowly idle its self down, this won't. And I was thinking since it's intermittent that it's an electrical problem. Like i said it will run perfect for a while and start acting up for a awhile and then be perfect again, temperature off the engine had no effect either. So I decided to check the TPS yesterday. First thing I did was just unplug it and ride. It seems much leaner at idle with it unplugged, have to leave the choke on for quite a while to keep it running and it has a slight hanging idle, that does come down. I think the fuel air mixture screw just got turned into much but I'm going to wait till my Merge fuel screw gets here before I do anything else cause I can't tell if I'm turning the screw or not with the crappy short little homemade screw driver I made to fit in there. With it unplugged I haven't had that stuck throttle felling yet but it's been so intermittent it's hard to say. The TPS is expensive so I want to make sure I actually need it and if I do is there any reason I just can't order a TPS from Sudco for this particular carb, isn't the Yamaha one just an over priced repackaged Keihin one anyway.

Just leave the TPS unplugged. Mine has been unplugged for 6 months now. Yes you can use a paper clip to read out the plug. Sounds like you are running lean at idle and need to adjust mixture screw and or change pilot jet

TPS will not do that to idle. You can certainly unplug it as Swede says to test. However, leaving it unplugged will not enable full advance at high rpm and the power will suffer.

You problem is a combo of a misadjusted fuel screw/wrong pilot and/or idle too high.

If you did the blue wire mod (to disable the neutral switching the CDI) that can aggravate the issue too.

However, leaving it unplugged will not enable full advance at high rpm and the power will suffer.

Thats probably why I never noticed a difference in power, I never ride at high RPMs. I should go out and see next time

My 08 YZF 250 had exactly the same problem. Went from a 42 to 45 pilot and played with the fuel air screw after I had disassembled the carb 2 or 3 time to clean all ports and passages. Works great now. With temp or altitude, I make 1/8 to 1/4 turn adjustments to my easy/longer/indexed fuel/air screw. :smirk:

Turns out it was the hot start. When I turn the bars all the way to the right the hot start was opening and staying open. When I put on my new radiators the cable got under the top bolt. Turning the bars back and fourth was one of the first things I tried but it was hard to recreate the problem on the stand cause if the hot start was already stuck open turning the bars had no effect. I just kept trying to compensate with the idle and fuel screw till it was all out of whack. Also only one section of my track is ridable right now and its 2 left corners so it always seemed to run good at home.

So my TPS was not causing the problem but I still think it might be bad cause the resistance at full open throttle is supposed to be 4-6 ohms if I remember correctly and mine was 3.5. Maybe it just needs adjustment to, I can tell it was removed at one time cause its been marked so it could be lined up again. I did find a post were a guy says you can order one for a Kawasaki, the internals are the same, just the wires come out the opposite sit as the Yamaha, and its a 3rd the price. Can any one confirm this will work?

You'd want to compare specs, call a kawa dealer and see if a mech there will give you the numbers.

Yes, a Kawasaki will work. I have one sitting in the toolbox which I had on my 05 YZ250F.

Electrically performing, wiring connections, and internal/externally mechanically, the part is the same. The is a difference though in the exit wiring though- The Kawasaki part is opposite hand wiring; the wiring exits to the front whereas the Yam exits to the rear (or other way around, I forget).

Letitride, Where are in you in MN? Maybe I can loan it to you? PM me if interested.

Hope this helps.

BazookJoe, did you have any trouble with the wires reaching. On my 06 the wires exit the TPS towards the front of the bike and there's not much slack any were. I don't realy see a way to reroute them either to get some more length. If it's not to much trouble could you measure the lenght of the wires on the kawasaki TPS, I'm just concerend that even though it fit your 05 It might not reach on my aluminum frame.

I looked up the price for a TPS through Sudco it was almost as much as from Yamaha, I'm suprised how much cheaper the Kawasaki ones are.

The wires are about 2" from the edge of the molded plastic to the near edge of the white connector. IMO, you could splice the wires and/or make an extension cord.

You have a good point about whether the aluminum framed bikes have enough wire slack to make it work. The steel frames are definitely different- I was just out to the garage to compare- The Yam alum frame TPS is the same configuration as the Kaw, but the wires are way shorter on the Kaw TPS.

Idea- If you look inside the TPS's white connector, the bullet ends release real easily and it would be easy to splice it longer. I worked with those type connectors when wiring the WR. And if you are interested, there is a place who sells the plugs/sockets/connections.

Here's a pic and hope this helps.


Edited by BazookaJoe

Thanks BazookaJoe, that just might be long enough to make it. If not I'll order the connectors and make a couple inch extension like you said that way I won't have to cut any of the wires on the bike or the sensor.

my 05 wr250f went from running great to missing and stumbling instantly. unpluged tps instant fix running great again :smirk:

LetitRide, Glad to help out.

CX613- I'm going to go out on a limb here, but I just have a hunch that the bike runs better with the TPS connected and that is why Yamaha chose to equip the bike with such a device. Just a crazy and wild thought...

LetitRide, Glad to help out.

CX613- I'm going to go out on a limb here, but I just have a hunch that the bike runs better with the TPS connected and that is why Yamaha chose to equip the bike with such a device that is properly adjusted. Just a crazy and wild thought...

Fixed the typo for you! :smirk:

no the tps quit working properly just wanted to say if you having issues with the bike stumble and missing try unpluging tps. will get new one but it did run fine with it unpluged. quick fix better than not riding that day!

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