Product DescriptionHow to distinguish AC fired or DC fired CDI box
1. In the GY6 6-plug set-up, you have AC if you have 3-wires going into the 4-plug side and you have 2-wires going into the 2-plug side. On the other hand, you have DC if you have the larger CDI box, 3 or 4 wires going into the 4-plug side and only 1 wire going into the 2-plug side

2. In general, the DC CDI's tend to be larger in size than the AC ones.For example ,the common AC fired CDI box is length 66 x width 38 x height 23 mm or length 58 x width 33 x height 23 mm ,but common DC fired CDI box is larger than AC fired cdi box in size ,such as length 75 x width 42 x height 23 mm or length 96 x width 55 x height 24 mm .Certainly this size is only for your common original CDI Box reference,don't include the racing cdi box size ,please note

3. Another test is if the headlights turn on without the engine running, (with just the key on), it is a DC system. In the AC system the headlight requires the engine to be running. Another indication is, if the engine will only run with a battery it is DC. If it will run without a battery, it is a AC system