[TR] TR3A plugs #3 and #4 running colder

[Rick]

I did a plug check on my TR3A today. While the front two plugs looked great
(light tan insulators), # 3 was much darker and #4 was sooty. Plugs are NGK
BP6HS. I seem to remember a discussion here a year or so ago concerning #4
running cooler than the other cylinders. I checked the archives, but no
cigar. Anyone remember this discussion? I'm planning to lean out the rear
carb a few flats (HS6s), but I'd rather do it with a bit more information.
Car runs fine, with only 800 miles since the rebuild.

 

Rick in Seattle

1960 TR3A

1970 BSA 441 Victor Special

1972 Norton 750 Commando Combat

1975 Norton 850 Commando Mk3