Yamaha TRX850 Enthusiasts Forum

Just taken the TPS of the std carbs and fitted to fcr's and have found since the taco is now stuck in calibration mode. With the taco reading 3,000rpm the manual tells me there is a short and when I move the TPS to either extreme of adjustment available I get either 1,000 or 8,000 readings so I'm only finding the short when try to find a happy medium(the 4000rpm) between these. Are they a cleanable item???
secondly....What is the function of this sensor? I realise it reads the throttle position but where does it relay the information to and what does this dictate???
It still runs ok still while in this faulty state(sending signal that the throttle is constantly open fully) but am still fine tuning the new carbs fitted and realise this may contribute to how things feel at present.

TPS change the ignition timings - when disconnected it fully advances the ignition.

If your FCRs have TPS, then my advice would be to use TPS. If not, you can mod the CDI to stop the tacho going into diagnostic mode.

Have a search on here and you will find:

- my dyno charts with and without TPS
- details on how to set TPS
- details on how to mod CDI

So, which modelyears were fitted with TPS?
I have one of the later ones (1999, black/red), but there's no TPS fitted. Surprised me a little.

that's strange !!! there is no mention of it not being fitted to any model in the yamaha manual

Mine is a 99 model(australian) as well and tps was fitted..(which is the one I took off to fit to the fcr's) Figured it had something to do with ignition timing. Do they still also run some other kind of auto advance system aswell as the TPS for ignition timing??. (use to the old bonnie with a centrifical wieghted advance and points).... thanks for the insight

Excuse me once again there phuk but I cant seem to find where to access dyno results and info,

steve speed wrote:that's strange !!! there is no mention of it not being fitted to any model in the yamaha manual

wot he said ^^^^, I was of the understanding that TPS was fitred to all TRXs

aaa hhhhhh. The search thingo up top, found your dyno results now just have to look for the other on setting tps. have manual and have gone from instructions there so far but still only have 3 options when adjusting. 1000,8000 or 3000... not enough, too much or full advanced while in short mode and taco dancing. Moving the tps a poofteenth seems to give me 1,8,or 3000 and cant seem to find that magic 4000. Noticed the surgy feeling under 4ooorpm when set at 3000(full advanced today). Will continue search mode for your setting advise phuk...
sorry for my computer illiteracy mate and noticed you've answered this question qyite some times.

for those who are interested, the threads are here

http://trx850.motomaniac.net/forum/view ... ilit=102.3

and

http://trx850.motomaniac.net/forum/view ... hilit=dyno

No luck finding anything on calibrating timing via tps adjustments through search incase I'm doing anything out of the norm, but seems pretty straightforward from w/shop manual. Seeing as I cant find that illusive 4000. Would it be best to opt for 1000 or 8000.
Does the 1000 mean it will reach full advanced upon opening the throttle earlier than if set at 8000. Have set it on there and taco has settled..I'll take it for a run and hopefully taco wont dance otherwise that says to me an intermittent fault(the worse kind).

steve speed wrote:that's strange !!! there is no mention of it not being fitted to any model in the yamaha manual

phuk72 wrote:wot he said ^^^^, I was of the understanding that TPS was fitred to all TRXs

Earlier I looked at the right hand side of the bike and saw some white filler cap on the carbs.
Today, I went to the garage and looked at the left hand side to the carbs... and guess what!
Waddayaknow, there actually IS a TPS on my bike!



Well, in my defense, I would like to state that on my YZF the TPS is on the right hand side of the carbs block.

you need to lay off the smokes young man ,,,,,,,and read the manual ,,,,,glad you sorted it

Well with the setting as close as possible still on the 1000 before moving to 8000,this has certainly smoothed out the power response under 3000/4000rpm and is pretty close to where it was living before around the centre of the adjustment slot.

No ideas out there on how to find that illusive 4000 in calibration mode though hey???? or wheather my assumption on gaining full advanced earlier by setting via the 1000 is correct????

Anyone else had this challenge thrown at them before when setting the tps and not been able to find the factory recommended setting of 4000 when adjusting???

All a part of the learning curve...

Did you ever find out what was going on with the TPS Cobba?

I've just picked up an Aussie model and have the same issue. I've set the TPS as far away from 1000 as I can before it jumps to 8000. (Which is along way from where it was originally set)

I'll take it for a run this afternoon to see what she behaves like.

Std ECU is a pain in the arse when it comes to the TPS.
Your ECU has set voltage values and you have to move the TPS on the carbies to get it calibrated to the ECU setting.
I fixed the problem by fitting a programmable ignition . Calibrating the TPS is done via the ignition unit and simple. It reads the voltage at 0% throttle click, and rotate the throttle to 100% click , on the calibrate icon and problem solved..