'72 R60/5 Ignition Coil Resistance Help Needed

[jsbrusso]

Hi all,
I am starting to restore a '72 R60/5 SWB. I'm in the process of pulling it apart now and got to the coils so decided to check the resistance on both of them. My Clymer manual says primary resistance should be (For Bikes with Single Plug Coils) .67-.77 ohms. Secondary resistance should be 3.7-5.3 K ohms.
So both my coils are a good bit higher at: 1.0 primary, and 6.6K secondary resistance. In other words, resistance in my coils is about 25% higher than it should be.
I checked both coils, with two different multimeters and got the same results. Anybody out there know if this is reason for concern? Thanks gang!

 

[20774]

I typically don't test individual resistances unless I think there might be a problem. If the ignition is installed on the bike...yours might not be...I measure the resistance from one spark plug cap to the other plug cap. For some of the later bikes, say /6 and /7, the reading cap-to-cap is usually about 20-22K ohms...essentially being 5K for each spark plug cap and 5K for each coil. For the early /5s...not sure if the '72 is in that group...the spark plug caps were only 1K ohms...making a cap-to-cap reading of around 12-14K ohms.

If you get higher readings than that...and you might...then be sure all the connections are clean. A higher resistance might make for a weaker spark.

 

[jsbrusso]

Thanks very much for that. The plug wires are toast, so they will get replaced anyway, but thanks for giving me a new method of testing system resistance cap to cap. Never would of thought of doing that.
John