engine misfires or dies under 3000rpm

[wagonweel]

Temporarily mounting something like this might tell you a lot ?

https://www.amazon.co.uk/XCSOURCE-Motorcycle-Waterproof-Digital-Voltmeter/dp/B01NAK5ENF

Looks like a good option to continue to use occasionally after this issue is fixed!

[wagonweel]

Ok, had a chance to do a test on the battery and this is the result:
Ignition off 12.9v
On 12.5
Starting dropped to 10.68 before recovering

Running 13.7 then once revs drop to idle 13.69
13.7 @ 3000rpm

After 10 mins idling 13.67
Fan cuts in 13.42
Fan off 13.57
Fan on 13.41
Off 13.55
On 13.40/38
Off 13.55/4

All up about 20mins idling.
Also, as an Australian model the headlights cannot be switched off (can umplug but illegal to ride like that)

Should have some time to check the other things mentioned(stator, rectifier readings) over the next few days.

Thanks again for all the responses

[SB]

The readings suggest that the battery and charging system are working correctly but it would still be interesting to know what the voltage  reading are when the problem occurs.

[Tarwdu]

My money would be on the rectifier.  Intermittent misfiring suggests the alternator putting AC into the system, especially when the rectifier gets hot.
A typical sign would be a cooked battery making you think the battery is at fault. Check battery electrolyte to see if its been boiling.
Its worth checking the rectifier connector block which may be corroded causing a high resistance.
Gareth.

[wagonweel]

My money would be on the rectifier.  Intermittent misfiring suggests the alternator putting AC into the system, especially when the rectifier gets hot.
A typical sign would be a cooked battery making you think the battery is at fault. Check battery electrolyte to see if its been boiling.
Its worth checking the rectifier connector block which may be corroded causing a high resistance.
Gareth.

Was running a voltmeter off the battery and charge stayed the same when it started to play up. The connecyor block looks fine

[wagonweel]

Ok, so the voltage stays between 13.6/7 and even when it starts to misfire/die.

What I have now noticed (didn't have my earplugs in) was there was that buzzing/radio static type noise whenever the bike stared to misfire. That is the same noise made after the ignition is turned on and thethe fuel pump does it's initial prime. Further, after I parked it the last time, when I turned tge ignition on tge fuel pump made that buzzing/static type noise only ... not the priming noise. So, I am thinking either the fuel pumo is on the way out, or there is a blockage and the pump is struggling or both.

Again, when the bike is hot, low speeds with lots of stop/starting and it first showed up after a tight turn and then quick stop.

Leaning towards fuel starvation?

It has been a long spell of hot weather here. Apart from 2 days ago, there hasn't been one ride since early August below 30°C with many 38-40+. Hard on electronics but also rubber piping I guess

[cristi-mic]

It should be fairly easy to do a fuel pressure check-up. Since your electric system is perfectly OK, the fuel pump is the only possible culprit. Stop changing parts like crazy....

[wagonweel]

Here is the latest.

I had a fuel pressure test done and told it was good/fine. However, the bike was running normally at the time.
The mechanic fitted a small light so I could see if the power to the fuel pump was cutting in/out when the issue occurs.
He also said the valve/flap (see part #3 https://www.bike-parts-honda.com/pieces-honda-detail-5696-13MBT3S1-XL1000V5-2005-F__1900-XL+1000+VARADERO.html ) isn't opening as it should around 5000rpm and put a small bypass for me to try when the misfire starts. Could this possibly point to an issue with the ecu?

Anyway, a few things I have noticed:
-After I park when it has been playing up it stinks of fuel/petrol. 
-Also the last time it started it's nonsense I wasn't wearing my earplugs and could hear the fuel pump making a strange buzzing sound as the engine was hunting/trying to stall.  This is the same noise it makes when the ignition is turned on right after the pump primes (sometime at the same time) but only after/when the bike has been playing up.

Next stop I'll have the fuel pump removed (nope the first thing I thought the mechanics would do) and check the contact points .... perhaps that buzzin/static sound that coincides with the misfiring is the contact points for the pump?   

We finally have lower temperatures here and the bike ran fine on an hour and half hwy run with a short section of slow moving traffic. Fingers crossed I can nurse it for the next 3 days as I'm relying on it at a big event. After that back to the shop again.

[SB]

There have been very few problems reported with the FI fuel pump so I'm not sure how it works.

The Honda manual says the pump output pressure should be between 320-370 kPa (46-53 psi) so it's clearly different from the Carb model and I don't think it has contacts and works the same way !

Looking at your most recent description of the symptoms I'm beginning to wonder if the problem is the fuel pump supplying too much pressure (not switching off) when the engine gets warm.

This could cause the engine to run rich and cause the stalling, smell of fuel and buzzing noise.

The Honda manual contradicts itself re the wiring of the "Fuel cut off relay". The fuel system section shows this simply being driven by the "bank angle sensor" but the wiring diagram section shows the "Fuel cut off relay" driven by the ECU so it may be that there are no contacts in the fuel pump and the ECU controls it.

The next time the problem occurs leave the engine running, pop off the seat and remove the fuel cut off relay. The pump should stop and there should be enough residual pressure in the system to allow the engine to continue running for a short time. As the pressure decays the engine should start running normally again before eventually stopping as the pressure drops below 320 kPA (46 psi.)

If this works it could indicate a faulty ECU or a faulty sensor (MAP, TP ?? ).  If there is a faulty sensor or ECU I would expect to see a fault code displayed by the MIL blinking when the ignition is turned on.

[wagonweel]

Ok, more confused now 😀

I will try to find the fuel cutoff relay mentioned next time it plays up....  see what happens and report back.

The latest is bike didn't want to start, eventually did but stopped then ran rough just like when playing up, butbut it has never done this from startup before. I was reading on another forum the exact same symptoms (rough running, stalling, fuel pump making a buzzing sound a few seconds into priming and smelling really petroly when you stop) and their fix was a fuel pressure regulator replacement (different bike).  I was wondering if there is a fuel pressure regulator that is supplying too much fuel (when playing up) but this wouldn't be noticed as much at higher rpm as it would be using more.


 It does seem to backfire on deceleration lower revs.

[SB]

I think it's clear that your problem is caused by incorrect fuel supply.
It's not clear to me what is most likely to be causing that as I don't know how the fuel pump is controlled. There is no separate fuel pressure regulator but there may be one within the fuel pump.

Your problem could be the fuel pump or it could be a problem with the map or throttle position sensor (or even the ECU).

[cristi-mic]

Again, my bet is on the fuel pump. There are NO points that wear out or other relays, only a small (kind of) filter and the pressure regulator is integrated in the pump.
Taking the pump assembly apart is something you could do by yourself. The pump inside is easy to replace, look for a model  SIDAT 70077 or BOSCH 79106.
The fact that it runs well sometimes basically eliminates all parts but the fuel supply. And the noise of the fuel pump is quite clear about the problem. There should be a slight buzz for 2-3 second when you turn the key, then the pump stops and later is impossible to hear because of the (awful) engine noise.

[mhenawy]

thats an interesting problem.
i suspect the rectifier but any updates from the owner ?

[Captain Scooby]

I have one permanently mounted. Always have. You know before you even throw a leg over whether or not it's going to start.
But back to the intermittent running. I'm stunned no one has tested the fuel pump for pressure. Wouldn't that be the logical approach?

[Captain Scooby]

Every bike should have one. Mine is permanently mounted.
Test the fuel pump pressure.