Tom,


I think that Wilbur's advice to give the carb a good cleaning is good.
From your description of tight space around the carb, I suspect that you'll
need to dismount the carb to do this. You can spray carb cleaner around ,
maybe it will work.
Many of the posters here live in the US and won't be able to advise you
on the composition of gas in your province. Ask some locals.

Dave M.