TPS Mod

gnrnr · Post by **gnrnr** » Sun Sep 30, 2007 9:08 am

Hi all,

I've been searching the new site for a while on the TPS mod, and how to do it, without any success. I'm guessing the information i was after was held in the old site which appears to be dead.

Can anyone show me the way.

I have a TRX-850 motor mounted into my XTZ. I've just finished up doing some rewiring and now my tacho is playing up (goes to about 4,000 then holds to 3,000 for a couple of seconds then drops back to zero, rinse and repeat) when the ignition is switched on, and I understand that this is due to the TPS not being fitted. Previously the tacho on the bike was wired into the coils, now I'm using the sender from the ECU. Does the TPS mod overcome this and how do I do the mod?

Regards

Gnrnr

Killerwhale · Post by **Killerwhale** » Sun Sep 30, 2007 9:34 am

gnrnr wrote:Hi all,

I've been searching the new site for a while on the TPS mod, and how to do it, without any success. I'm guessing the information i was after was held in the old site which appears to be dead.

Can anyone show me the way.

I have a TRX-850 motor mounted into my XTZ. I've just finished up doing some rewiring and now my tacho is playing up (goes to about 4,000 then holds to 3,000 for a couple of seconds then drops back to zero, rinse and repeat) when the ignition is switched on, and I understand that this is due to the TPS not being fitted. Previously the tacho on the bike was wired into the coils, now I'm using the sender from the ECU. Does the TPS mod overcome this and how do I do the mod?

Regards

Gnrnr

In the small contact connect the upper pin 1+2 to battery minuspole.
Pins are called GPS1+2

bobtrx · Post by **bobtrx** » Sun Sep 30, 2007 10:08 am

gnrnr go to TRX Mods + Upgrades page 2 , look down it to Head job page 2 there you will find tps with pics as given to me by trixynut

gnrnr · Post by **gnrnr** » Sun Sep 30, 2007 1:20 pm

Thanks guys for the help.

gnrnr · Post by **gnrnr** » Mon Oct 01, 2007 9:45 am

I got the picture and did a test with the wiring tonight. The tacho is still jumping about when the ignition is switched on, so the mod does not appear to be working as far as disabling the diagnotic funciton goes.

Is it possible that this is not working due to my bike having the 4NX ECU rather than the 4UN version?

Regards

Gnrnr

trixynut · Post by **trixynut** » Mon Oct 01, 2007 3:14 pm

Mate,
If you did the mod exactly as in the picture, this will definitely disable the diagnostic function on the tacho ("tacho needle jumping around") and set the igntion at full advance and raise the rev limiter.

If it's not working, either you've not quite done it right or it's something else i.e. you need the 4UN eurpoean version as you said.

Try it with the TPS connector removed: the bit that connects the TPS to the carb: black fryingpanshaped thing?

Dave.

gnrnr · Post by **gnrnr** » Tue Oct 02, 2007 12:25 am

trixynut wrote:Mate,

Try it with the TPS connector removed: the bit that connects the TPS to the carb: black fryingpanshaped thing?

Dave.

Dave,

There is no TPS wiring with the bike (the person I bought it off never connected the TPS, even though the carbs have the TSP fitted to them). I connected the GPS1 and 2 pins to earth. The SS pin was already dropped to earth to bypass the side stand switch. The SPD (speedo), VCC and VTA connectors were left open circuit. I wonder if the ECU is looking for the speedo as this is one of the speed restricted ECU's. As it is not fitted to a TRX, there is no way it will ever be connected to a TRX speedo.

I'd prefer to wire in the TPS, can you show me what colour wire goes where at the TPS end of the wiring? The Haynes Manual is very poor in that regard.

Previously the tacho was just wired straight into the coil wires, and I suspect the previous owner never saw the tacho moving around. If I have to i can get the tacho working by doing that again, but that still leaves an ECU in some sort of error mode. I have always had problems with it breaking down at about 6,000 rpm (I think it was actually dropping onto one cylinder), which is why I started rewiring it, only to learn that it has a speed restricted ECU fitted. The wreckers want over $400 for a replacement 4UN second hand one, but i'm not willing to do that without testing it first.

Thanks

Steve

devlin · Post by **devlin** » Tue Oct 02, 2007 1:40 am

Try this...... http://trx850.motomaniac.net/forum/viewtopic.php?t=595 .....last page

trixynut · Post by **trixynut** » Tue Oct 02, 2007 10:19 am

Do the standard xtz carbs have a TPS connection (I think they do). If they do, then the standard wiring on your xtz will have somewhere the tps wires needed to connect the tps to the carbs, if thats the route you want to go down. The bypass mod makes the tps wiring redundant.

You could try a 4nu unit off another trx if you can find one thats close by where you live I suppose, before you buy one.

Sounds like you're better off trying to put it all back to standard maybe: if the xtz carbs have a tps connection as the trx ones do, this should be reasonably straightforward (or as straightforward as any bike electrical loom matter ever is!)

gnrnr · Post by **gnrnr** » Tue Oct 02, 2007 12:29 pm

I've spent way too long looking at that part of the Haynes manual

The XTZ does not have TPS fitted normally. My bike is fitted with the TRX carb though. I looked through the manual tonight that Devlin linked to (thanks) and I may have a faulty ECU, connecting the TPS up will confirm this. I'm going to rewire the TPS in correctly later this week and see if the problem persists (if so I'll see me Doctor:)

Thanks all for your help.

Steve

wicky · Post by **wicky** » Tue Oct 02, 2007 12:33 pm

as far as i am aware standard XTZ 750 carbs (and TDM's from 1991-1995) do not have any form of TPS fitted.

TonyDevil · Post by **TonyDevil** » Tue Oct 02, 2007 3:05 pm

wicky wrote:as far as i am aware standard XTZ 750 carbs (and TDM's from 1991-1995) do not have any form of TPS fitted.

correct, the TPS was only fitted on the 270degree engine models, 4TX,4UN onwards etc

Sp!ke · Post by **Sp!ke** » Tue Oct 02, 2007 3:56 pm

The XTZ has no TPS locator on the carbs, its blanked off with no internal mechanism.

The XTZ doesnt have the loom for the TPS or the ECU either (the TRX has about 7 extra cables). So if it doesnt work then its probable that you need to double check the new wiring loom you created.

I've gone this route also with anXTZ but used TRX carbs and wired up the TPS so it works as I wanted to retain the powercurve.

Have you been to http://supertenere.proboards20.com ?

gnrnr · Post by **gnrnr** » Wed Oct 03, 2007 1:02 am

Sp!ke wrote:The XTZ has no TPS locator on the carbs, its blanked off with no internal mechanism.

The XTZ doesnt have the loom for the TPS or the ECU either (the TRX has about 7 extra cables). So if it doesnt work then its probable that you need to double check the new wiring loom you created.

I've gone this route also with anXTZ but used TRX carbs and wired up the TPS so it works as I wanted to retain the powercurve.

Have you been to http://supertenere.proboards20.com ?

Hi Sp!ke,

I've actually discussed your mods with you on the Suuper Ten boards. Obvioulsy I'm not to memorable

I didn't do the original conversion to this bike, I'm just trying to tidy up the loom. For reasons unknown the guy that did the original installation never hooked in the TPS, so there is no wiring in the loom for that. He had the tacho wired into the coil leads from the ECU as per the XTZ wiring. I have finally wired in the Tacho to the correct output from the ECU and am just trying to sort out the ECU so that it does not generate the error codes any more. I've tried the TPS mod which should disable the error reporting (since I don't have the TPS connected), but that did not seem to work. I'll have another look tomorrow night as I now have the service manual whcih shows me the correct pin wiring for the TPS. I'll hook that up and see if the error code goes away. If not I'll look at gettign another ECU as the manual suggest that if the TPS is OK and the loom iteslf is OK (not broken) then the ECU is at fault.

I'd prefer the TPS to be connected as this should improve the lower RPM running of the motor, which is good when off road.

What gearing are you running on yours Sp!ke.

Thanks all.

Steve

gnrnr · Post by **gnrnr** » Wed Oct 03, 2007 1:02 am

Sp!ke wrote:The XTZ has no TPS locator on the carbs, its blanked off with no internal mechanism.

The XTZ doesnt have the loom for the TPS or the ECU either (the TRX has about 7 extra cables). So if it doesnt work then its probable that you need to double check the new wiring loom you created.

I've gone this route also with anXTZ but used TRX carbs and wired up the TPS so it works as I wanted to retain the powercurve.

Have you been to http://supertenere.proboards20.com ?

Hi Sp!ke,

I've actually discussed your mods with you on the Suuper Ten boards. Obvioulsy I'm not to memorable

I didn't do the original conversion to this bike, I'm just trying to tidy up the loom. For reasons unknown the guy that did the original installation never hooked in the TPS, so there is no wiring in the loom for that. He had the tacho wired into the coil leads from the ECU as per the XTZ wiring. I have finally wired in the Tacho to the correct output from the ECU and am just trying to sort out the ECU so that it does not generate the error codes any more. I've tried the TPS mod which should disable the error reporting (since I don't have the TPS connected), but that did not seem to work. I'll have another look tomorrow night as I now have the service manual whcih shows me the correct pin wiring for the TPS. I'll hook that up and see if the error code goes away. If not I'll look at gettign another ECU as the manual suggest that if the TPS is OK and the loom iteslf is OK (not broken) then the ECU is at fault.

I'd prefer the TPS to be connected as this should improve the lower RPM running of the motor, which is good when off road.

What gearing are you running on yours Sp!ke.

Thanks all.

Steve

Yamaha TRX850 Enthusiasts Forum

TPS Mod

TPS Mod

Re: TPS Mod