Hi all!

I am stumbling with diagnosing an old Honda AC-CDI (G300 engine late 70 early 80, which has 3 connectors two go to a coil beneath the flywheel and one to the kill switch. The ignition coil seems to be build in the CDI, as the output is the sparkplug wire.

If you scroll a bit down you see the CDI-Unit:

https://www.jackssmallengines.com/j...00001-to-g300-1457696/c-d-i-unit-exciter-coil

Has anyone some hint how to go about diagnosing. After cleaning the coil (under flywheel), I get a small reading on a cheapo voltmeter, set to AC.

Thx for reading

 

If you are trying to measure output to plug with a "cheapo voltmeter" you have probably
fried the voltmeter, they are not meant to handle 10's of KV from ignition systems.

Regards, Dana.

 

If you are trying to measure output to plug with a "cheapo voltmeter" you have probably
fried the voltmeter, they are not meant to handle 10's of KV from ignition systems.

Regards, Dana.

Hi Dana!

No I have not tried to measure the ignition coil (which is inside the CDI) output. I have measured the coil generating the AC for the AC-CDI, which might be in the terms of 12-60 V or so (sadly no specs online?), though there is no battery and alike, just a pull starter.

 

The exciter coil will be low voltage at cranking speed. I doubt its a CDI unit, as CDI units have a HV exciter & a separate trigger coil. The coil most likely is driven by a transistor ignition module. To measure the Exciter coil voltage at crank use the circuit below, it wont be very high.

 

Hi Daryl!

Many thanks for the "Peak Voltage Adaptor" circuit. Have to get my hands on the parts and will reply asap.

It seems a pretty old AC-CDI, it says on the flywheel cover "HONDA CDI", strange enough it has no pick-up connector. Perhaps it calculates the ignition moment out of the received AC pulse(s)?

Mike

 

You can get a KV diode out of a microwave oven at the dump, but its a "crappy" diode.
Large Vforward. If my memory serves me I think you can get HV caps out of PC SMPS
at the dump as well.

I get laptops at dump that people throw because they are so compromised by malware
and no longer function real time. I once restored 13 systems from dump and gave
them to a church for distribution to families that could not afford one. Then dump
shut off all reclamation. Idiots. Lots of good stuff at the dump.


Regards, Dana.