They should do what they do in the GP and have a clock on the centre showing how much of the 2 mins is left, if a rider isn't ready, he's out. It works brilliantly in the GP, a few riders got excluded once and it never happened again. Generally speedway is run in such a slap dash way that (perhaps it should be renamed to this, slapdashway) that the 2 mins can easily end up being 3, yes I have timed it in the past (anorak!)