My LED circuit stops working after a bit
The dynamo produces 6v (nominal), the rectifiers drop 1.2V (2 x 0.6V) leaving 4.8V for the LED which exceeds the maximum rating. Its not a particularly good idea to run the LED at its maximum current especially if the supply could vary (as in a dynamo output). So choose a safer 'operating' current, say 300mA, which is below the maximum for the LED and dynamo.

 

This gives a value of resistance needed as    1.8V/0.3 = 6 ohms

The power rating for this resistor should be   0.3^2 * 6 = 0.54W - so use a 1W resistor to keep it cool.