Plug colours

[Ruairidh Dunford]

I like to run D21 plugs in L/C heads.

[Roger]

Hello Martin,
I have been focused on the carburetor as that is what I had replaced, this prevented me from looking "outside the box" as you suggested I checked the distributer cap and found a tracking mark from No.3 lead across the surface of the cap.
I replaced this with a good cap and new leads and  went for a run today. when I stopped to check all the plugs were the same colour as photos below of No. 3 and 4. This may not be perfected yet but at least it has sorted No. 3 plug, thank you again for pointing me in the right direction. Thank you to all the other replies even those that got me worried about broken rings and sticky valves etc. I had visions of major strip down.

Roger


  plug.jpg (Size: 93.58 KB / Downloads: 235)
  plug3.jpg (Size: 88.78 KB / Downloads: 235)

[Ian Williams]

If its a new engine I would suggest the rings are not completely bedded in and its burning a small amount of oil still. Only seriously oily engines show wet black soot.

[Roger]

Ian,
Yes the engine has covered just under 500 miles since rebuild, the oil consumption is very little and I am changing the oil frequently.

Roger

[Roger]

Hi,

This is just a follow up to show the mixture results using a Coloutune device.
I borrowed this from a friend and would like opinions on the results, as I have not used one before.
My apologies for the quality of the video. Here is the link Colourtune

Roger

[John Cornforth]

Hi Roger

I have used a Colortune in the past on my Seven (HC head, 14mm plugs).  The blue colour with occasional white flashes looks like what I would expect for a correct mixture.

The occasional missing flash when idling is also normal, in my experience.

During this test the engine won't be loaded much, except briefly whilst the heavy flywheel is sped up.  But in any case, the device is aimed at users setting idling mixture, with the assumption that the carb is correctly jetted/needled for higher revs and throttle openings.

[Roger]

Thank you for your reply John, I am pleased that you confirmed my own thoughts on the results shown.
It was not so keen to work on No.2 plug I then tried it on No3 plug where it worked ok.
Maybe the engine was hotter by then. I may try again after a run to warm things up to normal temperatures. I was using an adapter from 14mm to 18 mm on a LC head. I have also have an AN needle.

Roger