B100L ignition

[gps]

I am experiencing very little spark on the lower coil wire and am wondering if there is a way to test the coil or should I dig deeper and check under the flywheel. The top plug has good spark and when I put that plug on the lower coil wire the spark is barely visible. Any suggestions? Thanks in advance for all that respond. Cheers GPS

 

[jgmo]

The coil fires both wires simultaneously in what is called a "maverick" or waste spark configuration. So, if there is sufficient spark on either plug wire, the components that fire the coil (exciter coil, CDI, points, etc..) are probably ok.

The shop manual says to measure the resistance of the coil using an ohmmeter. It says to put one of the meter probes in the #1 spark plug end and the other probe in the #2 spark plug end. The book gives a specification of 8 ohms plus or minus 20%.

However, we have established here, among some members, and through "empirical" testing of known good coils that the resistance should be somewhere in the neighborhood of 31 ohms.

Something else to consider is the spark timing. If the spark timing is 'biased" for a hotter spark in one cylinder it might naturally cause a weaker spark to occur in the other so checking the timing would be in order here.

 

[william_m]

The same was happening to our motors (with a million hours on them) was the cam belt would stretch as little as 1/2 tooth and cause the bottom plug to waste away.