My old '72 Kawasaki F9 Bighorn dirt bike used surface gap plugs.
It also had a CDI ignition system that put out 50KV as well.
Typical 18KV ignition system just isn't hot enough to keep the plugs from fouling.
A surface gap plug is about the coldest plug you can get.
The CDI system on my F9 put out such a hot spark that I never fouled a plug, even when the nut on my primary gear backed out and milled a hole in the case, allowing gear oil to get sucked into the carb (2-stroke, rotary valve engine).
It would just wear out the plugs internally over time.
When checking the ignition system, it was never a problem viewing the spark.
On an 18KV system, you had to block sunlight to see the spark.
On that 50KV system, it was like looking at a welding arc. It snapped and crackled it was so hot. And if you got your hand too close, it would bite big time and hurt like a bitch.