I used a pto overrunning coupler on my big bike like this:
Over Riding Clutch 1-3/8 Female X 1-3/8 Male | Agri Supply
I had to modify it, and it has a little more "drag" when freewheeling than I'd like, but the price was right and it also is extreme overkill strength wise.
That clutch should be very smooth with very little friction. I bet you won't be able to tell a difference in the way it rides with the front chain on or off. However, you will notice some funky handlebar feedback when offroading and the front is actually pulling.