Like Mike, I have a 13mm drain plug. I have been running my A5 Tomos almost 2000 miles and I'm still pretty happy with it. I change the tranny fluid every 600 miles and the bike runs great! I am very careful to check my chain tension and do the necessary adjustments if needed. My moped will do just over 30 mph and that keeps me happy. I guess I got one of the good A5 engines eh? (sorry, I'm Canadian eh). I am glad to read that your A5 is feeling better and I hoped it continues to do so.