Secondary coil resistance

2 replies to this topic
  • Strattos

Posted April 01, 2008 - 02:53 AM


For the past 12 months I've been fouling plugs. Sometimes two in two weeks, sometimes two in two months. Intermittent which I finally traced to the secondary ignition coil on my '02 WR426.

Instead of 9.5 - 14.3 k - ohms i was getting 22 at the plug cap. Testing the coil with the plug cap off (just the end of the wire on the lead) it read 11 k - ohms, which was in range.

The resistor inside the cap gave a 10 k - ohm reading, which appears to be the problem. However, i've just fitted a new cap (which has 5 k-ohm resistance) and i'm still getting a high reading, although it's only slightly higher 17 k-ohms from coil to cap. I know this is higher than the manual specifies, but would it hurt anything? Could running a dodgy cap for so long have hurt the coil and caused to give a higher resistance reading?

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  • Thumper_Bloke

Posted April 01, 2008 - 10:35 AM


If the 9.5k to 14.4k is what the book spec'd, then this is probably without the cap. The cap itself, you are correct, should be about 5k ohms. And yes, ignition coils do break-down internally after a while, the best way would be replace with a new one. Do you have one from another bike or a buddy that you can borrow?

  • Strattos

Posted April 01, 2008 - 01:15 PM


Thanks Thumper. Jeez you were right about the test being done WITHOUT the cap. I overlooked that when reading the manual. Unfortunately I don't have a mate with the same bike as mine. I might charge ahead with the new cap, which has half the resistance of the old one and see if I'm still fouling plugs.


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