Chain keeps falling off
I have a bike with only a back derailleur and the chain keeps falling off.
At first I noticed this happening almost every time I shifted to the lowest or the highest gear even though I had taken my time making sure I had adjusted everything correctly. So I bit the bullet and adjusted the mechanism so that I cannot shift to either of those two gears. But it still happens sometimes that I'll be cycling, not even changing gears, and the chain will just fall off the front sprocket.
This isn't the kind of bike where I can move the wheel back to tighten the chain and I don't think I need to remove a link either because it actually looks pretty tight already.
What could be the cause? Should I take some pics?