You can slowly turn the crank without retarding the spark..I don't know what the rpm needs to be to retard it..If you turn the crank slowly back and forth it will spark several times..I used to time the engines with a non syncro igntion first, but found out that slow turning will not trigger the retard function..RC.....
Myself, Silent Spark, and C&H buy the syncro board from the same place.We all use different igniton circuits .Don't know what the other systems (Pro Spark and early Air Hobbies) use..The 3W and DA sensors will not trigger other systems....Reichmuth, now sold by D&B, is also different....