The CDI unit is the most replaced innocent part in two-wheeler servicing. It gets swapped because it is easy to swap, sealed enough that nobody can prove it was fine, and cheap enough that trying is tempting. Half the time the real fault was elsewhere.
What it actually does. Capacitor discharge ignition stores charge from the magneto in a capacitor and dumps it through the ignition coil primary when the trigger pulse arrives, producing the spark. It also holds the ignition advance curve. It is a sealed potted assembly - there is nothing serviceable inside.
How genuine CDI failure presents. Classically: the bike starts cold and dies once hot, then restarts after twenty minutes. That thermal signature - works cold, fails hot, recovers on cooling - is the strongest single indicator, because it points at a component whose failure is temperature-dependent. Also common: a rev ceiling the engine will not pass, and a spark that is present but weak and yellow rather than blue and sharp.
What gets misdiagnosed as CDI failure. Before you order anything, check: the kill switch and ignition switch contacts (corroded contacts are extremely common in coastal Mumbai humidity), the magneto pickup coil resistance against spec, all earth points including the frame earth, the connector to the CDI itself for green corrosion or spread pins, and the ignition coil. A failing pickup coil produces symptoms almost indistinguishable from a failing CDI, and it is a different part number.
Buying the right unit. CDI units are not interchangeable across models even when the connector matches physically. The advance curve is model-specific, and fitting the wrong curve gives you an engine that pinks under load or feels flat - it will run, so nobody notices until there is damage. Order by the part code on the old unit, not by vehicle name.
On brand. This is a line where we push customers hard toward branded stock. Varroc, Spark Minda and Uno Minda CDI units are original equipment engineering. An unbranded CDI may work for a season and then fail intermittently, and intermittent electrical faults cost more in diagnostic labour than the part ever saved.
After fitting. Clean and dielectric-grease the connector, secure the harness so the unit is not hanging on its wires, and check the earth path. A large share of repeat CDI failures are actually connector and earth failures that keep destroying good units.
We stock Varroc, Spark Minda and Uno Minda CDI units across two-wheeler and three-wheeler applications. Send the code off the old unit and we will confirm stock the same working day.
The clearest sign is an engine that runs when cold, cuts out when hot, and restarts after cooling. Before replacing it, check the pickup coil, kill switch, earth points and connector - they produce very similar symptoms.
No. Even where the connector fits, the ignition advance curve is model-specific. The wrong curve can cause detonation under load. Always order by the part code on the original unit.
We stock it. Send the part code for same-working-day confirmation.
