Dear Bill,

Again, thanks for your reply and for the advise. Just out of curiosity and for the sake of learning, I have always broken engines both ringed and ABC type by running them rich (4 stroking) for the first 2 tanks or so (more than 2 tanks if engine hesitates to run lean) and then alternating between lean and rich until it holds lean steadily ... you mention that this could damage an ABC type engine? can you please explain how this might cause damage?

Have a nice day and thanks again for taking the time to answer my questions [8D]