Its poorly

Went out on the s4 with the missus last Thursday as the whether was nice did around 60 miles with it running fine pulled in to a pub for a pint and crisps, an hour latter got back on the bike and it didn’t want to start, had to use the choke to get it running and now it wont hold a tick over. So whipped out the plugs which needed cleaning and set off for a test…it run ok for 5/6 miles and started running poor again and the s4 wouldn’t hold a tick over again? Pulled the plugs out again, noticed that they were quite black…so popped to the dealer who said that it was running rich and sold me some new plugs…put them in and the same happened…any clues to the problem and can you adjust the mixture, I see some adjuster screws in injector bodies, what are the standard settings…..?