Mielr said:
Luke chopped off the front of that Speederbike with his lightsaber, and that's what sent it spinning into the tree.

I see Gaffer has an avatar (finally)! ;-)

I was going to suggest that anyone who didn't have one should be disqualified! LOL!

That one is the last one where he cut the front off. So the whole sequence at least from depths of my memory is Chewy, Han(knocks the dude out at least), Luke(jump onto 2nd speeder), Luke (I'll take these 2... shoots at one, then the scout runs into a tree), Leia (hers speeds up to turbo knocks her off her bike, then he crashes into a stump) and finally Luke (on the ground with his lightsabre)