Duane....the original ABC engine was a Super Tigre .15 CL speed engine so naturally it wasn't throttled
ST developed the ABC to avoid the problems encountered with the (then) normal cast iron piston if the engine went slightly lean during a run. As I said in my earlier post, I do a very careful slow warm up with my Rossi 45 and even though it's probably only got about 20 hours of run time there's still a lovely nip. For what it's worth, none of my CL engines (cold start at full throttle) have any nip now.