Motorcycle Exhaust design-diy?

[ssray]

How hard is it? any links?
It would be downpipes and a collector for a largish twin with a off the shelf end can
Cheers
Ray

[ssray]

Prefer for free, its only an cheap bike but being a twin it could be doable.

http://www.ojzengineering.co.uk/page.php have off the shelf bends