I just got a 3 year old QLink XF200 with 24 miles on it, but many of the screws were very loose so I did a full tightening around the bike. Then, when tightening this particular screw the screw head broke free from the screw thread.

When I pulled the screw out it had a spring held in place by a center rod from the screw head. This obviously created a major issue when making the screw hollow on the threaded part by sacrificing the strength of the screw.

I used a little American engineering to duct tape this screw back on, and the bike worked fine, as nobody I have talked to can figure out what the hell a flimsy screw on that part of the engine actually does. Does anyone have a clue as to:

A) What damage this could have done to the bike?
B) What this screw part actually does?
C) How I can either fix or replace the part?

Thanks a bunch guys -- been having fun on this bike -- best 400 dollars I've ever spent.