westwood t1600 won't start?

The fuel hose on my T1600 was leaking, so I changed it. In order to get to the clip in the front, I had to undo all the screws holding the big black thing on the top with the spinny thing. I could then lift it about an inch to give me access.
However after putting it all together, guess what, I turn the key, the red light comes on and nothing else happens. What have I done wrong?

Iain
June 2009