The flasher unit works on the principle of a bi-metlaic strip. That is, the current passing through it to light the front and rear lamps and the green indicator lamp in the speedometer (2 x 10w + 5w) causes the strip to heat up and bend away from it's contact. When it cools down it re-makes its conbtact and the cycle starts again. That's what causes the clicking sound.
If you don't match the flasher unit and bulbs then you wont get the correct flash rate.
I have upgraded my lamps to brighter 20w bulbs for front and back with a matched flasher unit.
Sometimes, it pays to advertise.
REgards
TT