Topic: Coil Testing ?

[rddcw]

Trying to methodically check and adjust all mechanicals on my 74' CB 750 K4. Just completed refurbishing my Carbs. With the gas tank off, like to check the coils, spark plug wires and caps.

Is there a way to check these with a volt-ohm meter ? How would you test them and what would be the procedure ?

[Flyin900]

Yes there is a test for the primary and secondary coil measurements of each coil.
If you have a service manual or download one from this site it will outline the procedures.
There is also a high voltage test that requires testing the ability of the spark to jump a specific gap that will require more than a volt/ohm meter. Not totally necessary if the other specs on the coils are within specified tolerances.
If the coils pass the tests it is a good idea to replace the plug caps on the wire ends with new NGK caps for a fresh connection to your plugs. Just be aware that the new caps use a 5K ohm resistor in each cap and any new NGK plugs with the R designation also have a 5K ohm resistance built into each plug. If the bike needs D8EA plugs stick to those and not a DR8EA plug as an option.
When replacing the caps cut the old spark plug wires back 1/4" or so, depending on your extra wire length to expose fresh copper wire to the new cap, since usually the copper wire is corroded and not a solid conductor on the old wire /cap connection end.

[mrbreeze]

I use an old Chevy points distributor to check coils. Besides the dist. you just need a 12 volt battery, a plug & plug wire, and a couple of jumper wires. A vise comes in handy also.

[mystic_1]

Yup, test resistance between the small wires on the coil.  Should be around 5 ohms.

Remove spark plug caps and test resistance between plug wires, should be, IIRC, like 15k ohms.

Hondaman has a few things to say about the caps in this recent post:

http://forums.sohc4.net/index.php/topic,154074.msg1761975.html#msg1761975


Another test is to pull out a spark plug, plug it back into the spark plug cap, and then ground the threads to the engine block.  Now crank the engine with the kill switch ON and you should see spark.  (may want to shut off gas and drain float bowls for this test).

hth
mystic_1

[Don R]

Study hard and you'll pass.

[martin99]

This is the method I follow. Ignore the Dyna part (unless you've got a Dyna of course)

http://forums.sohc4.net/index.php/topic,17711.msg184209.html#msg184209

[rddcw]

Found an article on the Forum by Flybox1 on testing the coils and spark plug wires. With my Volt-ohm meter I tested the coils right at 5 ohms apiece.  Read between 18 and 19Kohms at the spark wire caps ( 1&4 and 2&3 ). The spark plugs caps individually read right at 5Kohms each. So looks like everything is good