The plot thickens.
Plugs 1 and 2 are OK. They have brown deposit after a run or after idling.
Colourtune shows a blue flame
at idle.
Plugs 3 and 4 have yellow deposit (not tan) after a run. Colourtune tune shows
yellow flame at idle and plugs become sooty.
So, cylinders 3 and 4 are rich at idle but lean when cruising. This doesn't
make sense to me.
I checked for air leaks at carb/manifold and manifold/block but everything is
fine. Also, no cracks in manifold.
I can't see how the ignition could cause this. Re-checked valve clearances and
everything OK. Disassembled carbs - everything appears OK. All I can think of
is maybe the water ways are blocked around 3 and 4, causing localised
overheating, or is that too stupid.
Adrian, driving a Toyota in sunny NC
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