Honda Activa: Diagnosing & replacing a faulty CDI unit

With fitment of the new CDI unit, my Activa requires just half a self to start and it’s performance has improved a lot.

BHPian anjanc_2007 recently shared this with other enthusiasts.

The CDI unit of an Activa:-

This unit works seamlessly and silently without showing its fangs for years and years ( OE factory fitted CDI unit has lasted me for two decades since 2003). But after it reaches a certain age in many cases it creates niggles and the user is perplexed as to whether the fault is with the spark plug, ignition coil or elsewhere. The first components be suspected are the spark plug or the carburettor. Thereafter if there’s no current supply, the spark plug becomes the prime suspect.

The CDI issue has very distinctive symptoms and can be very easily diagnosed to target its malfunctioning if such issues are faced. An Activs with a malfunctioning CDI unit refuses to start at the start of the day of use. Despite usage of all tricks in the book scooter doesn’t start. At times many selfs and at least 40-50 kicks could be required for the engine to fire to life. And then the most important fact is that the machine runs flawlessly throughout the day just requiring a self to get started. And again after resting for 12 plus or more hours, the same symptoms are observed. Sometimes, the user gets fed up in the morning and leaves the Activa back, taking some other mode of transport.

The OE factory fitted CDI unit

The OE factory fitted old (left) seen on its flip side and the aftermarket new Nippon India made CDI units side by side (new one costs Rs 690/-). Even the old rubber fastener had decayed after two decades and is now replaced. But if a replacement of the CDI unit is needed, its advisable to carry the fitted unit as sample to the spares shop, as the company had changed the CDI type during its model life.

“The old order changeth ushering in the new” – the new CDI unit is fitted

Another way of making the old CDI unit is to hit its body a number of times with the plastic head of a screw driver. But we must never hit it so hard so as to damage its plastic enclosure box.

With fitment of the new CDI unit, my Activa requires just half a self to start and it’s performance has improved a lot. The enhanced electric supply due to the new CDI unit fitment enhances the spark intensity and also results in better combustion of the air-petrol vapour mix supplied to the engine.

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