From the rule book:
30. Ignition System (Updated 12/14/20)
a. Unaltered B&S stock ignition part #555718 is mandatory. Only “GREEN” ignition module allowed. Maximum RPM: 6,150. Exception – Cadet Junior 206 class requires the use of unaltered B&S stock ignition part #555725 (BLACK in color). Maximum RPM: 4,150.
b. Coil or its position, other than air gap, may not be altered in any way. Coil mounting bolts must be stock and cannot be altered in any way to advance or retard timing. Attachment bolts and/or bolt holes may not be altered.
c. Spark plug: Only the AutoLite AR3910X spark plug UNALTERED in any way from the OEM (B&S service part number #84005196) is permitted. Spark plug must have the “AutoLite” and “AR3910X” identification on the insulator. NOTE: Technical Inspectors may, at their own discretion, at any time, visually inspect and retain a competitors spark plug and replace it with a new AutoLite AR3910X spark plug.
Sealing washer must be in place, unmodified from the factory.
Temperature thermocouple is permitted as long as sealing washer and/or cylinder heat shield with spark plug hole are not modified.