I believe that in my part of the woods the four wheelers will spook game whether or no they continue running.
I observed a pair of big toms in a hollow about 300 yards below me a couple of years ago. I was sitting in a treestand about 50 yards from a four wheeler trail. I watched the toms feeding and loafing in the hollow for about an hour and a half. All of a sudden two four wheelers came along the trail and I watched to see what the turkeys would do. They could not see the four wheelers and were about 350 yards away, but they turned and trotted the opposite way! I have also observed this with deer; not always but enough to convince me that the four wheelers will spook deer. Some of the hunters on adjacent property use them quite frequently, and my neighbor uses his all of the time on the farm. I prefer to walk in and have had deer cross my path only a few minutes after getting into my stand. If you are scent free and walk quietly into your stand the deer will calm down. Most of the deer I see after daylight were several hundred yards away when I get on stand and could not possibly know I'm there unless they see or smell me.