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1979 cCB750f spark problems

Ian L

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Hi, first post,my bike has a good spark on cylinder 1 but very weak spark at cylinder 4 ( same coil ) also cylinder 2 good spark cylinder 3 very weak spark again same coil , any ideas would be appreciated. I tried a newer spark plug that I know works and still the same,made sure the ht wire was firmly in the coil in the two weak spark plugs. I had the carbs cleaned last year so both cylinders having the same problem at the same time this year is a bit of a stretch.I have a multimeter but not sure what to check. Thanks in advance for any help or is more information needed. Ian
 
Probably bad coils. The problem is that each one of the pair requires the other one working to BOTH get a good spark, impossible any other way except one half of a coil being bad.

A test for that would be to swap the 1and 4 plug wires to opposite coil pins of the SAME coil, and the same with 2 and 3 to their coil, if the weak side switches then coil the issue.
 
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