The type of oil used may be part of it.
Is it fouling plugs?The plug look black?
The ones you saw may or may not be stock. Possibly they removed the oil injection and run pre-mix??
Does the rider putt around or wide open throttle?
It's prolly fine tho, Smoke means oil, could be worse I'm thinking.
2000 GNC 5N\
2001 GNC 9N \ 40+ class
2004 GNC 9N /
2014 rock crusher "GO tortoise GO!"
2016 Byrd Rooster
Father of the "11" time National champion,and worlds fastest woman ATV racer
A few fast LT80's
250R~300cc's
300ex
350 Rancher
Kymco Mongoose
Survivor of the 12 Hours of ATV America 04 and 05