Great and interesting intro Steve
The RD club are a great bunch, I go on their rallys...ahhh a 250B I had one of those back in the day...fantastic bikes they are too!
...Paul
Greetings vish
The older ones may have a carb, its a blue/grey looking thing behind the cylinder. No idea what an injector looks like ...sorry, never had a new enough bike !
yeah I would cut a suitable disc from metal and screw it on the back with exhaust paste between that and the exhaust
http://cgi.ebay.co.uk/Holts-Gun-Gum-Paste-EXHAUST-REPAIR-200g-/160350398928