Thanks , I did hear.Go to the source with a long dowel or ready rod etc. between the engine case and your ear to check noise/engine rpm relationship.Well, in practice this happens, but when recording with increased RPM, the noise of the discharge increases (mufler), suppresses the TUC TUC TUC ... and it is not very clear.
In the video I forced a low RPM in order to make the TUC TUC TUC clearer ... did you notice?