Complete Dyna-S kit dual fire with single coil. The required mechanical advance unit must be purchased separately. Note: Difference between Single & Dual Fire: - Dual Fire - This is the way the earlier, pre-Twin Cam, engines work. A single coil is used and both spark plugs fire simultaneously. This is the simplest system. The 'wasted' spark is sometimes said to be horsepower robbing. - Single Fire - This is the way the stock 00-up Twin Cam / M8 engines work. Two separate coils will fire the spark plugs independently and only the spark plug of the cylinder that is on compression stroke will be fired. It is said that these engines vibrate less and can improve power. The effects will become more pronounced with hotter cams and higher RPM. Note: For the single fire kit see 902527.

Fits: > 70-99 Big Twin models (excl. Twin Cam) and 71-03 XL Sportster