How can I test my CL77 coils?

geosar · Post by **geosar** » Tue Dec 07, 2010 11:02 pm

I have searched the website and apologize if this has been covered. How can I test my 40+ year old coils to determine whether they need to be replaced or not.

Thank you in advance.

George in Arizona

davomoto · Post by **davomoto** » Wed Dec 08, 2010 9:22 am

George, one way to do it is: Hook up coils, condenser, and points plate as it would be assembled on the bike. Get power to the positive side of both coils. Put spark pugs in the caps, and open and close each set of points, and you should get spark. there may be an easier way to do it, but this has worked for me in the past.

Davo

FluteTears · Post by **FluteTears** » Wed Dec 08, 2010 9:30 am

I have used this method as a guide:

How to test an ignition coil
This testing procedure is valid for just about any automotive coil. Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all of the wires to the coil disconnected.
You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil is defective.
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You can also rest an ignition by using a volt meter.There should be a little over 12 volts pulse, or a dip and peak in the meter needle, rather than a steady 12 volts, at the output,while cranking the engine.
A Multimeter can also be used to check coil resistance, short or open. Other coil-related calculations can be found at www.calculatoredge.com
I don't know about these people voltmeters but mine has 9v volts installed . That coil can produce 20kv at 100 mw now that would bother me a bit. So now how can we check this coil safely well start by shorting the output and check the primary for continuity that is all on a normal meter 0.75 is just plain wishfully thinking. The secondary can be checked by adding a split load of 1000:1 so you can check the voltage when a small 1.25v battery is connected and disconnected. if the load is proper then this voltage should give you the ratio of the transformer why it is called a coil i don't know. maybe because both primary and secondary are tie together at one point. note to see it for longer time add a diode and capacitor on the divider

Read more: http://wiki.answers.com/Q/How_do_you_te ... z17Wx4XS9k

geosar · Post by **geosar** » Wed Dec 08, 2010 10:09 am

Thank you for the quick responses. I need to get a battery and will give it a try.

teazer · Post by **teazer** » Fri Dec 10, 2010 12:50 am

I must have misunderstood something in that last post. Primary resistance is usually around 5 ohms on points type ignitions, 3 on race systems and down to 0.5 ohms on modern digital systems.

On an old bike I'd expect to see 4 to 7 ohms on the primary ie across teh two low tension connections