The Metralla is actually the street version for Bultacos . Very few of these made it to the US. I see no reason why you could not build a Sherpa into a cafe bike. If possible stay away from a fiberglass tank and go right to plastic and change over to a flattrack type seat with padding. The gear box will be your biggest obstacle as it is close ratio and will be pretty odd no matter how you gear it. Perhaps a Matador gear-set might work for you. Contact Hughes Bultaco, bultacomotorcycles.com and they can likely tell you all the pitfalls. For sure you want a Mikuni carb. The low pipe is available from several sources for flattrack. You will want to change the front brake at least. Try a Honda comstar cast wheel from the 80s/90s with a disc brake set-up. This sounds like a fun project
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