... 1.Small spark,safe BOSCH 91108 BSX 163-164 2-BS 163-164 ,dynastart carbon brush,starter carbon ... never appears scratch, rough, ablation and so on. (2) With a good flow properties and set to change ... original manufacturer's specification. Any more than a 2 degree variation in the setting can cause arcing, ... size of opening. BOSCH 91108 BSX 163-164 2-BS 163-164, dynastart carbon brush,starter carbon ...