Help narrow down a diagnosis

[BuzzBravado]

Trying to help my bosses son. He has a 2016 MT03 which has recently been causing him bother.

Twice now he has had to pull over on major roads as the the bike loses power. He describes it just like he has let go of the throttle. When it happens he pulls over pulls in the clutch and the bike just idles, if you try rev it nothing happens. Switches the bike off, leaves it 10 mins and it works again like nothing happened. Its not drive by wire as it has a proper throttle cable so he is definately opening the butterflies, so i cant think how it wont rev.

Yamaha suggested changing the TPS but they will only sell whole thottle body at £700 which is a lot for a young lad. The TPS idea makes sense to a degree.

Any ideas?

Edited by BuzzBravado on Monday 30th September 12:44

[gavgavgav]

-ve battery terminal loose? (its the cheapest answer and easiest to check)

[Jazoli]

Buy a used throttle body off ebay and swap the tps?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2...

Cheaper than 700 that's for sure.

[MK3 Dan]

Looking at those throttle bodies it does like it is drive by wire of sorts, like the R6's.

Whilst you have a throttle cable connected to the throttle bodies it just gives a reading to the sensor next to it. This is interpreted by the ECU and the motor on the other end actually opens the butterflies. This is why it will not rev even when twisting the throttle.

I would recommend fitting the replacement set of throttle bodies above.

[BuzzBravado]

I'll see if i can find a 2nd hand set in the UK. The ones JAzoli linked are actually mt09 bodies, and the others i can find are in USA.

https://www.ebay.co.uk/itm/2015-2016-Yamaha-Yzf-R3...

This is what the MT03 ones look like.

[Krikkit]

To be honest I'd pull the TPS off the bodies and see if you can find what model it is based on the serial numbers etc. You might find they're separately available for reasonable sums.

[BuzzBravado]

Could the TPS cause these symptoms if its not drive by wire, as in he can open the butterflies by cable? The MT09 bodies linked higher up do look drive by wire given the motor and lack of spindle, but MT03 (r3) bodies dont have the motor and have the spindle for the cable.

[Steve Bass]

BuzzBravado said:

Could the TPS cause these symptoms if its not drive by wire, as in he can open the butterflies by cable? The MT09 bodies linked higher up do look drive by wire given the motor and lack of spindle, but MT03 (r3) bodies dont have the motor and have the spindle for the cable.

If the TPS isn't reading the throttle plates being opened, it will not signal the ECU to add fuel in line with the additional air coming in. So whilst the throttle plate is opening, it won't be doing anything as no additional fuel or timing is being added. Hence it won't rev up when the TPS is lost. It also seems that the TPS reading is being lost by the ECU which sets the default to tick over fueling and timing when the bike glides to a halt when out & about.
A simple 1st step is to get some electrical contact cleaner and clean up the male & female sides of the contact pins. really get them cleaned especially the female side as even slight corrosion can cause the symptoms described.
If this doesn't resolve the problem, the TPS is easy enough to replace as a standalone item.

Good luck

[TommyBuoy]

Would a TPS error not throw and engine management light or limp mode. Did on my Ducati

Is it related to heat? When my TPS went it just went.

Like all intermittent faults, of you can replicate it you have a better chance of a true (e.i. correct) diagnosis

ETA - has Yamaha had it on a diagnosis kit? Also, it must only be out of warranty a little bit, could try speaking to Yamaha customer services

Edited by TommyBuoy on Monday 30th September 19:12

Edited by TommyBuoy on Monday 30th September 19:18

[poo at Paul's]

MK3 Dan said:

Looking at those throttle bodies it does like it is drive by wire of sorts, like the R6's.

Whilst you have a throttle cable connected to the throttle bodies it just gives a reading to the sensor next to it. This is interpreted by the ECU and the motor on the other end actually opens the butterflies. This is why it will not rev even when twisting the throttle.

I would recommend fitting the replacement set of throttle bodies above.

This. They are ride by wire, I think pretty much any newish bike is nowadays, needs to be to be Euro 4.

[Rubin215]

£700 for new throttle bodies which may or may not make a difference v's whatever his excess is if he just sets it on fire by the side of the road...

Sometimes the simplest solutions make the most sense...

[OnTheEdge]

poo at Paul's said:

This. They are ride by wire, I think pretty much any newish bike is nowadays, needs to be to be Euro 4.

The MT-03 throttle bodies use a conventional dual cable control, not drive by wire.

[BuzzBravado]

TommyBuoy said:

Would a TPS error not throw and engine management light or limp mode. Did on my Ducati

Is it related to heat? When my TPS went it just went.

Like all intermittent faults, of you can replicate it you have a better chance of a true (e.i. correct) diagnosis

ETA - has Yamaha had it on a diagnosis kit? Also, it must only be out of warranty a little bit, could try speaking to Yamaha customer services

I was surprised when he said no codes, and no EML. I dont think it is heat related as it happened one time as the engine was still warming up. I can see why heat could be part of it though, like a dry solder joint. He has tried to make the fault happen as we know intermittent faults are nigh on imposible to resolve via a 3rd party.

Our local Yamaha dealer in Edinburgh is beyond useless, always have been. More interested in selling assless chaps to thier Indian customers and good specialists are thin on the ground here. I was going to suggest a car auto spark.

Before trying to get a TPS i just wanted to check the general opinions on whether a faulty TPS could cause those symptoms. I've had bad TPS on cars before but the symptoms are usually bad running, poor idling. Wheras this runs fine, and when the fault happens it idles fines, albeit will only idle. Doesnt even cough.

[leighz]

intermittent fuel pump issue?

I'd be tempted to check the fuel pressure between pump and carbs/injectors