|Leaking Marchesini wheels
I fixed my front wheel on my 1100 Sport that was leaking air through a porous spot in the casting. Here is what I did...
Since the leak had grown over time, mainly since the last tire change, I dismounted the tire to have a look inside for signs of wheel failure. I didn't find any, or any real reason to explain why the leak had gotten worse, except that maybe some of the paint on the inside of the wheel had been rubbed off, although this wasn't obvious. There was a somewhat porous looking spot in the area of the leak, just inboard of the rib on the bead area that is supposed to retain the tire if it loses pressure. I sanded it with 120 grit down to bare metal and applied a thin coat of JB Weld. Presto - no more leak.