I believe that it is all in the way that you hunt that counts.
The person in my opinion with the closest real answer would be Jrbsr.
Now in my own defense, I don't physically own a four wheeler, but I do own a pick up truck. Where I hunt, which isn't very far off the road - due to limitations from a couple of automobile accidents, I park the truck within sight of my tree stand and I have had some success in the past couple of years.
But the thing that helps me is that there is a natural gas well directly below my tree stand and there is someone that maintains the gas well on a weekly basis and someone that comes from time to time to empty the brine tank beside the gas well. So between the township road, which might get 5 automobiles a day and the gas well that might get two vehicles a week, and not many people has actually shot at these deer to spook them, they don't pay an automobile any mind as long as it is moving and not stopping.
I have hunted turkeys and small game there in the past and have seen deer standing on a ridge not 100 yards from the gas well - watching the gas well attendant do his work. I'm sure that with their natural attraction to salt that if the brine truck driver spills a little salt water on the ground that they will come down and lick it up. I have seen deer that will walk over to a gas well brine tank and lick the salt off the pipes - on a leaky tank.
My advice is to get there two hours before you can legally hunt.
Give the game plenty of time to get used to you driving back to your stand and remain motionless on your stand before it gets light outside and you will be ok. Deer can see you and your four wheeler even better in the dark then they can in the light. The headlight will always give you away. Deer can see in the dark just as well as they can during the day time. So parking it a distance away from your tree stand - just to keep the smell away and then having to walk 1/4 of a mile isn't going to make that much of a difference to them one way or the other. After a while, they will associate the sound of your four wheeler to a hunter in the woods and they will be more cautious when they approach that area.
So basically when you ride to your stand - you are training the deer to know when you are going to be there. Deer don't look up, they look out. So just because you don't see them looking up at you when you are sitting in your tree stand doesn't necessarily mean that they don't know that you are there. It just means that they are willing to tolerate you - just like the deer I was telling you about that goes down to the gas well to look for a little salt after the truck driver leaves. Truck noise - gas well man, truck noise - a little salt on the ground. Four Wheeler noise- hunter.