I have this same problem. Only leaks when bike is turned off after a run out. I reckon it's the petrol left over in the hose that's leaking out and not petrol from the tap. With the bike running/ vacuum on, I think the petrol wont have a chance to sit and weep out whereas it would with the bike off. Also, it only seems to leak a similar amount everytime and the tap doesn't leak with the hose off. I reckon it's just my fuel hose not sealed around the nipple properly.

Should be one of those pain in the arse tight butterfly clips on it. I always get cut to ribbons on the edge of the tank trying to get the bloody things to move!

Well I been having a closer inspection and the diaphragm does have a very small nick in the first seal. I will report back when the kit is fitted and up and running.

Well RO kit arrived and fitted. Just need to fit to bike and run it up. when I removed the complete diagram the last diaphragm has a tear in it where it fits into the ali holder. No wonder it was leaking.