Sooty Spark Plugs

[dizzyrascal]

Hi

Re Sooty Spark Plugs

Can anyone please point me in the right direction, I have an 1100 which has just reached 60.000 and runs really well.

I have just undertaken a service and all is well with the exception of the spark plug colour, both plugs have sooty black deposits and not the nice tan colour that is normally found. I have to say that when I last removed the plugs they were darker then before but not as bad as they are now.

As i say bike runs well no problem setting up the fuelling with balancer and valves all at correct gap, but obviously something is not right. I thought originally that the bike is running to rich and started to think around what would cause this however doing a bit of a search I have come across the suggestions that this could be caused by the coil not operating correctly.

With this in mind I have decided to consult the oracle ( this forum ) I am sure that someone will have seen this before and hopefully point me in the right direction, there are no other symptoms but now that i know that things are not right I want to find a solution.

Thanks in advance

 

[MattW]

Has the fuel consumption worsened?

One thing that could cause your sooty plugs is the CO2 potentiometer possibly failing or having had its adjustment changed although this is unlikely to appreciably worsen the fuel consumption as it only affects low rpm fuelling.

 

[littleredrooster]

The only thing the colour of the plugs tells you relates to the last half-dozen turns of the motor. So if the last thing you did was to start the bike up from cold, run it for half-a-minute on choke, then the plugs would be dark.

The only true reading is to do a 'plug-chop'; with the engine at operating temperature, keep it accelerating under load for more than just a few seconds and kill the engine, coasting to a stop. Then look at the plugs and see what colour they are.

 

[uncle dick]

The only thing the colour of the plugs tells you relates to the last half-dozen turns of the motor. So if the last thing you did was to start the bike up from cold, run it for half-a-minute on choke, then the plugs would be dark.

The only true reading is to do a 'plug-chop'; with the engine at operating temperature, keep it accelerating under load for more than just a few seconds and kill the engine, coasting to a stop. Then look at the plugs and see what colour they are.

What he said really. With fuel injection etc. the engine cutting is not as important as it once was, so just take for a decent ride - say 3 or 4 miles on an A road - then stop and whip 'em out. Anywhere from mid brown to fag ash grey is fine.

 

[dizzyrascal]

Spark Plug Colour

Hi

Thanks for the replies I will try the test and remove the plugs as recommended, should have mentioned that my bike is fitted with a Lambda Sensor therefore could this be a possible cause if it is malfunctioning.

I was out on the bike yesterday and it is running great idles smoothly at 1000 rpm, the acceleration is nice and crisp and cruises nicely at 80 - 85 without any vibes. If i did not carry out my own servicing and had just paid the money to the garage i would be a happy bunny and oblivious to the colour of the spark plugs because I would not have seen them.

i have not noticed any change to the petrol consumption but having said all of this I would like to know what has changed to affect the condition of the plugs between the 6000 mile service intervals, up to about 12000 miles ago they were always the desired tan colour.