MKE FE wrote:
Coast to the shoulder and check the plugs are a light tan. Black is too rich, white is too lean.
Yes, that is the way we used to do it in "the bad old days." I'm reluctant to defend that position now.
If the engine is stock and in the condition reflecting the tolerances of the original era I would probably say it's okay if the color was a tad
darker tan. I doubt that the engine would stumble at stoplights, and climbing to higher elevations might lean the motor out anyway.
With modern tolerances, or in a rebuilt motor with more modern NOS parts, I'd be really careful. I'm not even sure that oil pumps of that era worked to the demands of the loads in the 1970s, much less today. I've found that everything is hotter and leaner. And if I miss my questimate I might even make things dangerously lean.
There are so many modern variables. Like sparkplugs, and more efficient ignition systems with hotter and fatter sparks.
And let's face it, when we were kids we used to run the bikes, stop for a beer and then rub our fingers inside the tailpipe. Then all of our buddies--none of which were mechanics--would comment on the 'color' and then have another beer...