5-Pin AC CDI Box for Chinese 50cc–125cc Engines

5-Pin AC CDI Compatibility Guide

This brand-new 5-pin AC CDI ignition box is a replacement for Chinese 50cc, 70cc, 90cc, 110cc and 125cc 4-stroke engines used in ATVs, quads, dirt bikes, go karts and mini pocket bikes — including models like the 3125B, 3125R and 3125XR8. It controls ignition timing and fires the coil so the engine runs smoothly.

CDIs are not universal. They differ by AC or DC type, pin count, plug shape and timing. Bring in your existing CDI (or ignition coil) and we will match it to the right one before you buy.

Specifications

• Type: AC CDI (powered by the stator, not the battery)
• Connector: 5-pin — one green square plug with 5 male pins
• Engine: Chinese 50cc, 70cc, 90cc, 110cc and 125cc 4-stroke
• Size: 64 mm x 37 mm x 21 mm (2.5″ x 1.5″ x 0.8″)
• Condition: Brand new

Compatible Vehicles

• ATVs & Quads: Most Chinese 50cc–125cc ATVs with a 5-pin AC CDI, including 3125B and 3125R models
• Dirt Bikes & Pit Bikes: Chinese 50cc–125cc dirt bikes, including 3125XR8 and similar models
• Go Karts: Select Chinese 50cc–125cc go karts
• Mini & Pocket Bikes: Select Chinese mini and pocket bikes

Fitment varies by year and model, so always compare against your original CDI.

Which CDI Do I Have?

• GY6 50cc–150cc scooters & ATVs: 6 pins in two plugs — one 4-pin and one 2-pin. See the GY6 50cc–150cc AC CDI →
• CG 125cc–250cc ATVs, dirt bikes & go karts: 6 pins in square plug housings. See the CG 125cc–250cc 6-Pin AC CDI →
• Chinese 50cc–125cc ATVs, dirt bikes & pocket bikes: 5 pins in one green square plug. (This page)

Still not sure? Bring in your old CDI and we will match it for you.

Signs Your CDI Is Going Bad

• No spark, even with a good spark plug and coil.
• The engine cuts out once it warms up, then restarts after cooling down.
• Misfiring, backfiring or popping under throttle.
• The engine will not rev past a certain point.
• Hard starting that gets worse over time.

No spark can also come from the stator, ignition coil, kill switch or wiring. Bring your ATV, dirt bike or go kart in and our service department will find the real cause — basic diagnostics are free.

5-Pin AC CDI FAQ

Is a 5-pin CDI the same as a 6-pin CDI?
No. The plug layouts and wiring are different, so they are not interchangeable. Count the pins on your old CDI — if it has six, see our 6-pin AC CDI for CG 125cc–250cc engines.

What is the difference between an AC and a DC CDI?
An AC CDI is powered by the stator, while a DC CDI runs off the battery. They are not interchangeable — using the wrong type can keep your engine from running. Bring in your old CDI so we can confirm which one you need.

Will this fit my 110cc ATV?
It fits most Chinese 50cc–125cc ATVs that use a 5-pin AC CDI with a green square plug, but not every model. Bring in your existing CDI and we will compare them side by side.

Do you have it in stock?
We keep CDIs in stock at 2916 S Santa Fe Ave, Los Angeles. Call (323) 588-6634 to confirm before you come in.

Can you replace it for me?
Yes. Our service department works on Chinese ATVs, dirt bikes and go karts every day. Call (323) 588-6634 to book an appointment.