2006 yz250f tps removed Help re installing

mx724
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mx724
Pretty simple but the manual is a bit confusing?

1 does the bike need to be running? Pretty sure it does per the manual?
2. How do I physically adjust the tps when the carb is on the bike? You cant get to it, its tucked behind the frame spar? You cant loosen the screw to adjust the tps when the carb is mounted? I must be misunderstanding how to get the reading the manual calls for?

Thanks guys!
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mx724
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mx724 4/18/2021 4:33am
4/18/2021 4:33am Edited Date/Time 4/18/2021 4:36am
I have a multimeter. The manual states to use the black and yellow wire and look for dcv .50-.70. I get nothing? However Should I be doing this with the coupler disconnected and bike not running Or connected and bike running?

I did get the proper ohm readout using the blue and black cable on the tps sensor side (coupler disconnected no bike running) It also appears that there is a bright blue marker like on the tps and carb to align by eye. Maybe this is good enough?

Just need some insight on how best to put the tps back and adjust if needed.
Paw Paw 271
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Paw Paw 271 4/18/2021 7:49am
4/18/2021 7:49am
It should not be running to set the TPS. Setting the TPS is the reading of voltage from closed throttle to WFO. .5 volt at closed to about 5 volt at WOT. You may only get about 4 volts at WOP.

Paw Paw
Paul_Pitzonka
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Paul_Pitzonka 4/18/2021 10:21am
4/18/2021 10:21am Edited Date/Time 4/18/2021 10:26am
You need a 5v reference input into the tps to set it to the desired voltage... you can do this with an external power supply connected to the tps with the bike off or with bike running at idle and a piggyback harness that allows you to read the output voltage... if you don’t have the ability to set it that way there is a formula that allows you to set it by resistance (which normally ends up fairly close to required voltage)... measure total resistance of the circuit (blue to black wire) multiply this number by .17 and that’s the rough required setting (within a few ohms) of the tps output at idle (black
To yellow wire)... it also doesn’t hurt to check to make sure your tps works full range of the switch...
mx724
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mx724 4/18/2021 11:23am
4/18/2021 11:23am Edited Date/Time 4/18/2021 11:24am
Paw Paw and Paul, you guys know your stuff Ive seen many of your posts. Here is the odd thing, Even with TPS unplugged bike doesn't run noticeably different? Bike runs ok with the choke on(TPS unplugged), soon as I cut the choke it dies. I've tried adjusting the idle as well as the fuel screw with no real impact. It did have a 42 pilot in there and I'm in the process of swapping that for a 48 but haven't tried that yet.

I cleaned and blew out all jets and or replaced. New Fuel screw Oring as well. Never had this issue with a carb, Always have had success with them.

After reviewing the 2006 manual It notes that there is a blue mark on the carb from the factory and the TPS unit, to line back up. How accurate is this? I'm pretty much in alignment with the carb mark so I wonder if maybe that is good enough?

I'm no electrical expert. When you say measure resistance I assume you mean Ohms? That was the only read out I could get and it was across the blue to black wire.

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Paul_Pitzonka
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Paul_Pitzonka 4/18/2021 1:09pm
4/18/2021 1:09pm Edited Date/Time 4/18/2021 1:22pm
No way you can eyeball the tps adjustment by lining the mark back up it’s too fine of an adjustment... you should see resistance (ohms) across the yellow to black wire as well if not either you’re on the wrong scale (should be 20k if you want to check full range of the switch) or the the tps is possibly bad... the older carbureted bikes could be run with the tps disconnected it just eliminates the timing curve (this won’t effect your idle problem)... your running issue to me sounds more to me like a plugged pilot circuit... the mid carb on the older fcr’s would get plugged with old fuel/ dirt and sometimes the only way to clean the carb without completely dissembling the body and waiting for an oring kit is with an ultrasonic cleaner... some other areas of the fcr that may cause your running issue is the vacuum slide plate either being worn or having a bad oring.. also a plugged squirt nozzle can present a problem (but they will normally still idle off choke) the 42 on the pilot shouldn’t make the bike not idle but may be a little lean depending on your elevation
Paw Paw 271
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Paw Paw 271 4/18/2021 1:46pm
4/18/2021 1:46pm Edited Date/Time 4/18/2021 1:47pm
On EFI bikes the TPS is "must be adjusted correctly item", but on a carb bike like yours you will find it will run good even if the TPS is disconnected. In an EFI bike the TPS has a big effect on the fuel delivery, but on a carb bike this is controlled by the carb jets.
Run a wire through the carb pilot jet to be sure they are clean. They can look clean and still be clogged with a clear dried fuel deposit blocking the small side holes in the jet. Blowing it out will not clear them.
Be sure that the fuel screw is set from 2-2/12 turns out from fully seated when you first start the bike and then adjust as needed.

Paw Paw
mx724
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mx724 4/18/2021 2:16pm
4/18/2021 2:16pm
Paul, I got some fresh gas and dropped in the 48 pilot and surprisingly ran much better. Very minor bog off a hard snap of the throttle running the fuel Screw 1 1/2 turns out.

In regards to the reading across the black and yellow, I could never get a reading, but that was just with the coupler unplugged and no 5V source that you spoke of(also no mention of that in the manual?) Regardless, it might simply be bc the reading is so low my volt meter has the auto decimal, maybe it didnt pick it up?


Paw Paw I was under the same impression that TPS on a FI bike was far more precise than a FCR carb'd bike. One I dropped in the 48 and some fresh gas it ran well, then I plugged the TPS back in and really seemed to make no difference, just letting the factory marking be the guide.

mx724
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mx724 4/18/2021 2:20pm
4/18/2021 2:20pm Edited Date/Time 4/18/2021 2:42pm
Paul would you mind sharing a little more about how to use the 5V reference? Id be interested to know if I come upon the need in the future. Id like to understand more. Appreciate the insight from both you guys.
Paul_Pitzonka
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Paul_Pitzonka 4/18/2021 2:49pm
4/18/2021 2:49pm
Take an adjustable power supply or any dc source you can regulate down to 5 volts ( I made a portable one out of a 9v battery and a cheap adjustable buck module) hook the positive to the input leg (blue wire) on your tps and the negative feed to the ground leg... measure the output (yellow wire) from the tps with your multimeter; this is where you will see the .5-.7 volts loosen the screw and rotate until you’ve reached your desired setting... this method is great for bench setting throttle bodies as some of the modern efi bikes it’s almost impossible to access the tps while it’s on the bike or at least while the bike is completely assembled... As mentioned above the tps on a carbureted bike isn’t as important as an efi bike but it still has an effect on the overall performance...
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Paul_Pitzonka
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Paul_Pitzonka 4/18/2021 3:08pm
4/18/2021 3:08pm Edited Date/Time 4/18/2021 3:12pm
I didn’t see your prior post on the pilot jet... it’s possible it was just that lean (I see you’re in Cleveland which is close to sea level and I’m assuming fairly cold at the moment which would both attribute to a richer jetting requirement... just a side note but sometimes a larger pilot can mask another problem causing a lean condition... the initial bog you mentioned is very common on fcr’s there’s a few things you can do to help it but most people just live with it...

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