So installed new exhaust and down pipe to my 125 virago, however the jubilee type clip used to secure the downpipe to filter box does absolutely nothing it seems, exhaust gasses still come out the gaps and can't see why it would make a seal, any ideas what I can use or do, I've pushed the downpipe in as far as it can go and seems almost too narrow to make a decent seal.

The female section normally is a tight fit, or has slots/sawcuts down the length, so that when the clip is tightened, the cuts close up onto the male section. Its also typical I believe, to use an exhaust paste to tkae up any gaps/space between the two mating sections. Fit the paste before mating the sections, then tighten up the clip. The paste normally hardens off when the system gets hot, and seals the two sections

Paste sounds good I'll give that a go, cheers