I have a first generation Strida. The belt spools off the rear pulley. I turned the belt around thinking that if it was due to the belt, that it would spool the other way, but it didn’t. Now I’m thinking the pulleys are misaligned. Is there an adjustment for that? What else could it be?
I have no direct experience of this problem, and I don’t have a Mark 1 strida, but it occurs to me that maybe the belt is too loose if this can happen. A properly adjusted belt will tend to stay where it is in my opinion.
If the belt is tensioned correctly, is everything running true? Could the BB have slewed around in some way? I know the earlier generations of Stridas had BB carriers that were bolted onto the frame. This is just like a blind man guessing, but it’s the sort of thing I would look for if it was mine. Upturn the bike so the wheels are up in the air and pedal the bike by hand and try and get a sense of what it is that makes the belt try to walk off the pulley. Then you may get a clue as to how to put it right. It seems to me that a properly adjusted, straight running belt should stay where it is.
If its a Strida1 the rear pulley has 2 flanges (one each side) but the Front pulley has only one … and the belt tries to ‘run up hill’ towards it. As commented above, the belt tension is important not too much and not too little as in manual and tips.
So, if the belt is spooling off sideways on the REAR pulley is the outer flange missing ?
This outer flange is a press/bonded fit to the pulley - but if badly worn it may have worked loose - if so … epoxy or superglue back. Look after that early rear pulley as they are pretty rare now.