One spark plug black the other fine after 2 minutes

[Guest aageaage]

When I run my NC700X for 2 minutes the one spark plug gets black and the other i OK. There is at smell of gas and the smoke is white.

The dealer have meseured til data and they are equal in regard to the flow to both cylinders. The electrical system should also be fine.

No other dealer and workshop i Denmark have seen it before. Any idees?

 

NC700X 2012
65.000 km

 

Flemming

Edited October 18, 2016 by aageaage

[ted 5,744]

Swap the plugs around, does it still do it on the same cylinder?

[JanneB 15]

Could be coolant leaking into the cylinder. Broken head gasket?

[Guest bonekicker]

Yes swop the spark plugs around--don't jump to expensive conclusions --so did the dealer not sort the problem out for you??? thats his job surely?? perhaps not ??his job is to just to sell  the bike--sorry dealer for presuming that you may just care a little for your customer !!!! 

[Rocker66 34,476]

Yes swop the spark plugs around--don't jump to expensive conclusions --so did the dealer not sort the problem out for you??? thats his job surely?? perhaps not ??his job is to just to sell  the bike--sorry dealer for presuming that you may just care a little for your customer !!!! 

The bike is 4 years old with 65000km on the clock so probably not under warranty. Unless the owner asks the dealer to fix it and pay for it then it is not the dealers responsibility. They are not a charity

[Derek_Mac 1,404]

 How's the compression in each of the cylinders?

 

Edit: Also, is the plug that goes black actually black and wet?

Edited October 18, 2016 by Derek_Mac

[DaveM59 1,605]

Eliminate the obvious.

If you remove the 'good' plug cap, will the engine start on the 'dud' cylinder? If so then it's firing so the electrical part is OK and you need to look at mechanical stuff. It'll run like a pig but you should get some life from it. If it won't fire at all then put the lead back and...

Swap plugs.

Swap HT leads.

Swap coils.

If the fault stays on the same cylinder the item you changed is fine and you can leave it there. When the fault swaps cylinders you found the faulty part. 

If having swapped everything you can with no change in faulty cylinder then the fault is either mechanical such as head gasket, or the ECU isn't firing the coil on that cylinder. Then it may get expensive and harder to fault find.

Again don't go whipping heads off before checking compression and cylinder drain down and if that is OK then the problem is back electrical and harder to find without dedicated equipment.

Edited October 18, 2016 by DaveM59

[Guest aageaage]

OK! the dealer is actualy working on the problem and is also getting the dedicated equipment to test the ecu. He has spoken to all the other Honda dealers in Denmark about the symptoms and no one have seen the same. That is why I´m looking for answers outside the small market for bikes we have here in Denmark.
 

Honda in Denmark offers 5 years warranty - but of course thats dependent of how Nellemann see things. The rear wheel bearing was not included in that warranty. They broke down after 40.000 km. The swiches and the spedo was covered.

[Tex 36,817]

Could be coolant leaking into the cylinder. Broken head gasket?

 

Yes, the white smoke would lead me to suspect the same. I would definitely be doing compression tests and so on. Doesn't sound electrical to me.

[Guest aageaage]

Just to let You Know. After a long and disapointing waiting for an a solution to this problem from the danish importer of Honda MC, it seems that they have found at fault i the system (ignition/ HISS). I will let You know the exact facts later. I have been told that the cause is not mesuable, so they swop the parts from another machine in order to test if the assumption is/was right.

[trisaki 2,029]

Do you  know when the valve clerennes were last done if itso a 700 should be every 8000 miles if 750 every 16000 miles  first thing I would  check 

[Guest aageaage]

The dealer has done everything to solve the problem. Unfortunatly has the danish importer of Honda Motocycles Vilh, Nellemann told the dealer that neither Nellemann or Honda knows the solution. This was on 5th og december 2016. After I have confrontet Nellemann 26. februar 2017 a nice salesman did try to help.

The Serice Manager at Nellemann, Jesper Carlsen has taken the bike to Jutland after long time. Nellemann will change the  ECU as it seen that this solves the problem. Unfortunatly they do not have an ECU, the only one avaible has an ETA 10 of April 2017.

There is something rotten in the state of Honda Denmark!

Edited April 2, 2017 by aageaage

[Guest Mac750]

That's a shame, but glad the fault was identified eventually.  We have very good Honda dealers in the UK, we also have very bad ones. The trick is to find the good ones and name and shame the bad.  Honda UK (the importer) have helped some of the forum members and others like myself only got lip service, a roll of the dice. Hope you are back on the road soon .

Edited April 3, 2017 by Mac750

[Guest aageaage]

The machine will be delivered to me next week from the dealer who by experience Honda owners is considered the best Honda mecanic in Denmark. The symptoms are not measureable with the standard procedures and was detected by swoping ECU from a working NC 700 to mine.

 

Hope the information will be useful for other membres if ever the symptoms happens to them. 

Of all the bikes I have had, The NC 700 has given my most fun: (70.000 km i 3 small seasons. From Polar circle to middle of Portugal.

This Year it vil be 72 FIM Rally 2017 Sundsvall, Sweden.

Do please vist 74. FIM Rally Roskilde 2019 which is beeing planed by me and other motorcyclist.

74th FIM Rally Roskilde Denmark 2019

Happy Easter

 

 

 

[embee 7,288]

It's extremely rare for ECUs to fail these days, the manufacturing methods and quality control are such that build faults don't get through and in-use failure is almost unknown. Having said that, anything is possible.

 

As I've said before, by far the most common and likely problem is with connectors. When they swapped the ECU I wonder if they swapped it back for the "faulty" original one to check the problem returned, and preferably swapped the "faulty" one onto the donor bike for the "good" ECU? Does the fault move with the "faulty" ECU? Quite often simply disconnecting the plug/socket and refitting it will cure the problem, but of course if you just swap the ECU and leave it then it is concluded that the ECU must have been faulty. All rhetorical questions really, just good fault finding practice.

 

Whatever, as long as your problem is solved then that's all you are interested in.

[Tex 36,817]

I once had someone tell me (in a voice full of wonderment) that he had tried his 'faulty' ECU on a different car (Suzuki Vitarra) and it had worked perfectly. But it wouldn't work on his own car. And neither would the 'good' ECU from the second car. He asked me what his next move should be? I suggested a job behind the cheese counter at Sainsbury's.

 

Two minutes with a multi meter showed the crank sensor to be faulty (btw).

[Grumpy old man 4,682]

Arrrh. ...Give me a BSA bantam. K.I.S ( KEEP IT SIMPLE )

[Guest sykospain]

Last year I had the Crank Position Sensor go duff on my otherwise perfectly-reliable Skoda Fabia estate car.  The fault completely paralysed the vehicle and also totally confounded the local mechanic's workshop.  But the following day it was spotted immediately by the Skoda dealership, simply by plugging in the Diagnostic lead -  and the faulty sensor was immediately replaced at a cost of a hundred snoojits.

Edited April 16, 2017 by sykospain