I thought riding with the enrichner full on (principally) could foul the plugs.
Over the years, I've done it for an hour or so (eventually, you notice the bike's lost some power), never all day.
My plugs seemed fine (I never pulled any to look). Probably burned off any carbon.
For a long time now, one of my (every time) checklist items is to make sure I didn't leave it on (again).
I've also been known to ride away with the gas OFF. Lots of fuel in the lines, but soon enough she stumbles (and you smack your forehead and reach down and switch it ON). That's on the checklist too.
