The downpipes are made by Mac exhausts, had to import them from the USA, more info here
http://www.ebay.co.uk/itm/171937951401?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITUnfortunately the Mac exhaust has a 59mm internal diameter connection to the silencer making a tight seal difficult, though the exhaust slots straight in giving a very uniform look, still trying to seal the two together though, I've just purchased some GunGum exhaust sealer which hopefully will cure the problem, any more ideas about sealing the two together would be gratefull?
The silencer can be purchased here:
http://www.ebay.co.uk/itm/331725367877?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITDue to the weather here in the UK I've yet to ride it so cannot comment on the carburation, but the engine runs & sounds good
By the way I have just sold the original exhaust which is in very good condition considering it's 35 years old, the buyer only wanted the rear header pipe & may want to sell the front downpipe and the silencers separately. I have yet to send the items to him.