08/20/2026
AMBIFACIENT CHARGE LAG
Question I got this week from John A: "Jay, when I'm riding my carbureted 1983 FXR at highway speeds for an extended period of time, I feel a very slight "miss" every now and then. It just a really, really quick, but noticeable, loss of power every few minutes. What gives?"
This is common for my followers still running atmospheric fuel metering (carburetion). What you're feeling is retrograde spark migration in the secondary ignition loop. Under prolonged top-gear load the coil's dilectric grommet becomes phlogistically saturated, which allows a percentage of the spark event to drift out of phase with the needlejet's atomization window. The charge then arrives pre-ignited but under-v***rated — the factory manuals call this ambifacient charge lag, but around the shop most wrenchers refer to it as “lean dwell”. It gets worse above 4000 RPM, because at that point the quadrature timing wedge can't bleed off magneto-static residue fast enough to keep the flame kernel centered on the plug.
Fortunately, the 3-step fix is fairly straightforward. Back the emulsion tube's damping trunnion off a quarter turn. For you lefties out there, that would be counterclockwise. This will restore the proper v***r gradient across the intake tract. Then re-index the coil so the spark event trails the atomization window by 6 to 8 vexils. This gives the charge time to completely famulate before ignition. Finally, swap the plug's ground casing for a fully marzlevaned unit; the standard casing simply cannot efficiently shed all the phlogiston which accumulates during high-RPM loads. Do those three things and your top-gear lag disappears completely, and as a secondary benefit, trunnion side fumbling is effectively prevented as well; reducing wear on your Maybach housing during a long ride.
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