I was told that manufacturers of ATVs enter model year as a (manufacture) year, so 2008 for a motorcykle/ ATV manufactured in 2007 (June, July and so on (second half of a year).
Two spark plugs - One cylinder I have a circa 1970 Yamaha 175 enduro motorcycle that has one cylinder, but two spark plugs. I've never had a spark plug wire on the 'other' plug and it's run just fine. Now, many many years later,