Yamaha TRX850 Enthusiasts Forum

I've now got my TRX motor into my XTZ and apart from a couple of minor issues like the rather severe clutch it seems to be running ok(ish).

One question I have is how one adjusts the TPS. I stuck it on so it works without the rev counter freaking out but I'm pretty sure there is a more scientific way of setting it up correctly. The bike runs ok as it is but its far from perfect, with quite some degree of hesitation at about 4.5k once past that it suddenly kicks in and off she roars.

Sp!ke wrote:I've now got my TRX motor into my XTZ and apart from a couple of minor issues like the rather severe clutch it seems to be running ok(ish).

One question I have is how one adjusts the TPS. I stuck it on so it works without the rev counter freaking out but I'm pretty sure there is a more scientific way of setting it up correctly. The bike runs ok as it is but its far from perfect, with quite some degree of hesitation at about 4.5k once past that it suddenly kicks in and off she roars.

I THINK it was....ignition on....yank the TPS contact out....put it in again....read the tacho....when at 4000 rpm it´s just right....ignition off/on again.

This is taken out of memory.....someone with a haynes might check it out!

Killerwhale wrote:
I THINK it was....ignition on....yank the TPS contact out....put it in again....read the tacho....when at 4000 rpm it´s just right....ignition off/on again.

This is taken out of memory.....someone with a haynes might check it out!

That's correct. The Yamaha manual states:

Turn the main switch to "ON"
Disconnect the TPS (Throttle position sensor) coupler
Reconnect the TPS (Throttle position sensor) coupler
[Machine goes into TPS adjustment mode.]
Loosen the adjustment screws (Needs a tamperproof torx screwdriver if I recall correctly)
Adjust the TPS Position
[When the angle is correct6 the tacho reads 4000 rpm, When the angle is too wide it reads 8000 rpm , when the angle is too narrow it reads 1000 rpm]
Tighten screws.
If I recall correctly it's pretty binary when adjusting, ie it's right or wrong.

You can download the Yamaha Manual from the downloads section btw.

TPS advances or retards the ignition according to the position of the throttle: full open gives full advance and vice versa so set up is important and could account for the flat spot then surge characteristics.

Burty is right re: setup, all done with bike NOT running, but ignition swhtch on.

Or, go for the TPS override mod to set at full advance all the time, but benefit might be limited with standerd carbs.

Dave.

The tacho leaps about only when its incorrectly set doesnt it?

Ah well I obviously read it wrong. I'll have a bash at it over the weekend.

Must admit, this bike is begining to be rather silly in a fun kinda way. Jeesh its loud too !!

Yep, only leaps about if it's incorrectly set OR if it's not working i.e. disconnected wire somewhere, so it thinks it's unplugged.

It's well worth it Sp!ke. My XTZ has the TRX motor in it and is the best thing ever. I'm just finishing up a re-furb (new rings and valve stem seals).

Mine doesn't have the TPS leads in at all, but I'm planning to fix that too.

When the revs get up over about 6,000 the bike seems to loose spark or drop ont one cyclinder.

Not sure if this is coil or tacho related yet, but is definiatly electrical. The tacho goes spastic when it plays up.