Tracy, During the time I worked for Kawasaki, (early 70s to 80s) there was a tremendous change in
the style of ignitions used on two cycles. The real culprit was sealing the engines and making
them pump better, but that is another story. Early ignitions were CDI using a power hungry DC to
DC step up converter to charge the capacitor. Single spark system was used with "surface gap"
spark plugs. The ceramic insulator and shell were the same depth the electrode was a bulls eye in
the center. The reasoning was the CDI could fire through anything and wouldn't foul. WRONG! The
problem found by many was the carbon would build up and a track would form, the spark would follow
the track and not fire the mixture. Conventional plugs with a LARGE gap were then tried, and even
with a .075 in gap they would build a carbon whisker from electrode to side wire, same problem.

The solution was better oiling and cylinder sealing, they then used an electronic ignition, (not
CDI) with greater success. The problem seen with high levels of TEL in 100LL is lead trace fouling
the same problem we saw in early CDI. Yamaha racing department had an advisory on using 100LL in
the race engines mentioning the problem of lead fouling. If you run a low compression engine with
a rich mixture of 100LL you will have tracking fouling or whisker fouling unless you run real hot
plugs. Even then you can have problems. By 1975 several Japanese manufacturers were recommending
ELF unleaded race gas for their two cycles. High octane with less fouling resulted. I hope we see
100 unleaded some time soon.
Bill Jepson

 
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