9 The stock two-terminal ignition coil (left) is what’s known as a dual-fire ignition coil. Daytona Twin Tec’s three-terminal single-fire ignition coil (right) eliminates backfire and enhances idle quality. The single-fire ignition uses separate coil windings and electronics to fire each spark plug independently. Spark firing occurs only on the compression stroke. With a dual-fire coil, when the rear cylinder is fired on the compression stroke, the front cylinder is on the exhaust stroke. But when the front cylinder is fired on the compression stroke, the rear cylinder is already on the intake stroke. Under some conditions, a combustible mixture may exist in the rear cylinder at this point and the wasted spark causes a backfire through the carburetor. It was highly recommended that I use Daytona Twin Tec’s ignition setup to compensate for the performance engine mods and Mikuni carburetor.