Tony Maico did have some 4 stroke experiments underway at one stage but nothing came of it to my knowledge. A number of home made conversions were on a website somewhere but I can't find them. I've got an idea that this bike is by someone called Viertak or something like that but to find out for sure I've passed on the photos to Ulrich my ex Maico factory mate in Germany. If anyone knows what the bike is, he will.