NC750SD power loss and mpg drop

[Grumpy old man 4,670]

27 minutes ago, Steve Case said:

Excuse me for ignorance, I will chastise myself later. But there is only one intake port and one throttle body, is that correct?

 

Which along with the fact the gent said he changed the filters rules out fueling surely?

I automatically thought he meant the 2 oil filters in the DCT bike.🤔

[Steve Case 939]

'I automatically thought he meant the 2 oil filters in the DCT bike.🤔'

 

Nil points, take yourself outside and give yourself a stern talking to!!

[Jamesc 3,640]

Apart from fuel filter, the service manual says for 'poor performance/poor economy':

 

*Check fuel system (e.g. including fuel pump, pressure regulator, MAP sensor, injectors..);

*Check air filter;

*Check ignition system.

 

So there's a whole raft of things it could be. Sorry I'm not narrowing down any, but the only way is to go through all possibilities methodically or spend time at the dealers (if Tallinn is anything like my local dealers, I would not put much hope in that option)

Edited September 24, 2021 by Jamesco

[Steve Case 939]

surely any of those things going faulty on the fuel system would ping up a MiL warning lamp. They are either working or they are failing cannot be both.

[Steve Case 939]

pressure regulator?

[Jamesc 3,640]

You'd think so Steve, but maybe the offender is not quite buggered enough yet to flag up the fault light...

 

Pressure regular part of the fuel pump assembly

 

To test that you could run a hose to a container and prime the fuel pump to measure how much comes out, and/or hook a pressure gauge up & take for a ride...although needs the correct equipment to hook into fuel system

Edited September 24, 2021 by Jamesco

[Steve Case 939]

Ah fuel pressure I understand.

 

But its one throttle body so a fuel problem would affect both cylinders, and I am assuming from whats been said before it was a misfire on a cylinder or were both cylinders playing up equally?

[Jamesc 3,640]

I think whatever it is, it's on both cylinders Steve - saying that only cos both plugs fouled

[SteveThackery 3,090]

This discussion illustrates the difficulties with diagnosis-by-Internet.  All anyone can offer is suggestions.  What it really needs is someone to actually diagnose it.  The difficulty is that intermittent faults are a total sod to diagnose at the best of times.

 

The reported sudden loss of power (but not complete stoppage, note), combined with increased vibration, made me suspect (and still suspect) that it is dropping down to one cylinder.  I might be completely wrong, of course, but it seems to me like the best fit for the reported symptoms.

 

The plugs are reported as "light coloured soot" and then "the electrodes are black with soot".  That does suggest a slightly rich mixture, but in my experience I've never known soot actually stop a plug from firing.  Wetness, yes, but not soot.  Others may have different experiences.

 

IF it is dropping down to one cylinder, it seems most likely to be an ignition problem, as the fuel system is common to both.  In the absence of actual diagnosis, it would seem logical to swap out the plugs, plug caps, leads, and coils, in that order.

 

FI systems can, in theory, compensate for blocked air filters because they measure the mass of air entering the cylinders and meter the fuel accordingly.  However, most motorcycles don't use mass air flow sensors; they infer the air mass from the throttle opening, intake absolute pressure and engine rpm.  As a result of this imperfect system I suppose it is possible that a blocked air filter could cause a rich mixture.

 

In this unsatisfactory situation, where a remote diagnosis isn't feasible, I would begin by fitting a new air filter, new plugs and new plug caps.  Then I would ride it around to see what it's like.

[Jamesc 3,640]

Very true @SteveThackery, my comments are just guess work from a distance. As I write this I'm working remotely from Tbilisi 😆

 

I notice that the American forum had some similar threads 'loss of power in 6th gear', diagnosis was "small engine" 😆🤔

Edited September 26, 2021 by Jamesco

[Grumpy old man 4,670]

Any news/updates on this?

[Marti 4]

39 minutes ago, Grumpy old man said:

Any news/updates on this?

 

Yes. Sorry for the delay, I've been to work.

There have been some developements.

First I'd like to thank you all. Your thoughts have guided me to keep searching for the ghost in the machine. 

Long story short:

Changed the air filter again - nothing.

Then I measured the primary and secondary resistance of ignition coils as suggested in another topic somewhere. They seemed ok, at least they were equal on both sides (if I managed to measure it right).

But then I bought a new battery because the old one had some difficulty starting on cold mornings and didn't keep the voltage so good anymore. 

And it cured the problem for a while. However, the machine still seemed a bit sensitive. Fuel consumption remained high for longer than normal after accelerating until it dropped again.

But yesterday I got caught in the rain and the ghost came back. (The ignition caps were dry inside, I checked). So I let the battery charge for the night.

Today there was some odd smell when idling coming from the center or back of the bike. A bit like burning oil and wires or something electric under heavy load. Ride home was a bit better than on worst days but not as good as just after changing the battery. 

Since its the end of the riding season here and the technician cannot be reached before the end of the month I plan to go through all the wire connections next. 

But what do you think? Could it be something with the charging system?

 

[davebike 943]

I would be look at charging voltage may not be the cause but a worry 

I would get a cheap volt meter block and add it where you can see it may tell a tale

Oh compair it with a know good multimeter as there £4 on that auction site and some are not that good !

ANother way is an app fro Andrid like Torque  a Honda to OBD2 adaptor and a OBD2 / bluetooth unit  Now you can moniter lots of real time info via you phone also read / clear fault codes

Edited October 4, 2021 by davebike

[jeremyr62 2,537]

I didn't realise the NC had an OBD2 port. Where does that live then?

I have a Bluetooth unit already for the car (OBDLink LX).

[Xactly 5,335]

2 minutes ago, jeremyr62 said:

I didn't realise the NC had an OBD2 port. Where does that live then?

I have a Bluetooth unit already for the car (OBDLink LX).

I think he means there’s an adaptor (Honda to OBD2) then use OBD2 to Bluetooth. Similar to Fiat 3 pin to OBD2 as available for some Moto Guzzis.

[jeremyr62 2,537]

I wanted to know where the actual socket is on the bike?? 

[Slowboy 20,345]

1 hour ago, jeremyr62 said:

I wanted to know where the actual socket is on the bike?? 

On my 700 it was a red plug behind the battery access panel in the Frunk.

[davebike 943]

Port is a red plug on top of the LSH of the battery  You need an adaptor to conbert to OBD2 socket but the software is compatable

My bike NC750X and MSX125 grom both have them fitted and Every Android device with bluetooth works well

I other adaptors at work for other makes only Hassle is nO adaptor and of course BMW nees a GS911 interface dongle £££

 

[Grumpy old man 4,670]

30 minutes ago, davebike said:

Port is a red plug on top of the LSH of the battery  You need an adaptor to conbert to OBD2 socket but the software is compatable

My bike NC750X and MSX125 grom both have them fitted and Every Android device with bluetooth works well

I other adaptors at work for other makes only Hassle is nO adaptor and of course BMW nees a GS911 interface dongle £££

 

Vroom! Something just went right over my head. Not your fault Dave I'm a technophobe.

[Jamesc 3,640]

On the American forum that thread I mentioned above with 'loss of power in 6th gear' was resolved by replacement of throttle body + the MAP / TP sensor unit

 

That would not explain any burning smell though @Marti, I hope it is just the smell of rain water on hot exhaust or similar

 

[Xactly 5,335]

7 hours ago, jeremyr62 said:

I wanted to know where the actual socket is on the bike?? 

Then ask that!

[jeremyr62 2,537]

1 hour ago, Xactly said:

Then ask that!

I thought I did. 

[Slowboy 20,345]

1 hour ago, jeremyr62 said:

I thought I did. 

So did I. 😉

[Marti 4]

4 hours ago, Jamesco said:

On the American forum that thread I mentioned above with 'loss of power in 6th gear' was resolved by replacement of throttle body + the MAP / TP sensor unit

 

That would not explain any burning smell though @Marti, I hope it is just the smell of rain water on hot exhaust or similar

 

Well yes. It could have been some water. Anyhow I haven't found any burnt connections so far. 

And for some reason I can't access the American forum (some firewall nonsense).

But conserning changing important parts, it feels like without proper diagnostics next, this could turn out to become a needlessly expensive hobby. The NC is simple enough to to do some basic maintenance by oneself, but I'm afraid this is starting to get a bit out of my league. The problem almost dissappearing after new battery and then returning again still puzzles me.

Wanted to do a valve clearance check but couldn't find the right feeler gauge from local car shops. They all have only 0.05mm steps. NC needed some 0.17mm and 0.28mm or smthg if I remember correctly. 

I guess my only option is to play with the multimeter some more until I get to see a technician.

[davebike 943]

To set 0.17   0.15 is loose 0.20 will not go !