I own a Strida 5.0 that I bought a few years back in Japan. It is a lightweight folding bicycle that, despite its single speed and unusual riding position, I find quite enjoyable to ride. I've taken to riding it up and down the Monon Trail.
The other day I began hearing a tic-tic-tic. The following day it became louder; I could feel it through the pedals. Concerned there could be damage inside the crankcase, I took it to a bike shop. They hadn't seen such a machine; there are apparently no Strida dealers in Indiana. They suggested hitting the drive belt with some WD-40, which had solved trouble on another belt-drive bicycle; they pointed out the belt seemed slack.
Back home I tried to tighten the belt, but the tightening mechanism won't budge, and I don't want to force it. In looking through StridaForum.com, however, I read of some similar trouble. That got me looking at my Strida's snubber. The snubber, which prevents the belt slipping of the rear wheel's freewheel gear, had a bunch of crud on it. After scraping that off, the noise has vanished!
I do need to buy a torque wrench and some fine grade lubricating oil for the bike. Buying a metal freewheel is something else I should do, but my plastic one looks good right now.