So I searched this one in the KTM threads:
O-ring chain vs. Non o-ring for KTM Dual Sport and found nothing. I've been running non o rings for years, just because when we used to road race back in the 80's the o-ring just meant more drag. My mechanic - Tom Houseworth (of yamaha fame) said:"you don't need the o-rings, they create too much drag". Well those words echo in my head every time ...