At highway speeds, all four plugs are light tan (one is a little lighter). Running around the neighbourhood, plugs 2 and 3 soot up quickly. Plugs 1 and 4 are a deepish tan. After 10 km of this kind of running, the bike will stutter and idle poorly.
Done so far (for this and other problems):
Checked sparks with new plug - colour is violet, spark is rather thin on all
Battery is 12.7v at rest, 14.5v on max charge
Carbs cleaned and synched
Fuel/ air mix is standard
Idle is 1,000 rpm
Swapped coils around - no change on #2 and #3 (secondary resistances are 12.65 k and 13.25k, both primaries are 2.9 ohm)
Cleaned and lubed advance mechanism
Corrected timing
Pulser generator gap adjusted; checked resistance (530k on both)
Switched spark units = no change
Any suggestions on what to check next?
