'The lot' means 'everything'. So, instead of picking and choosing your toppings and garnishes for your hamburger, you can simply ask for a hamburger with 'the lot'.
This is the contents of a typical Australian 'hamburger with the lot':
· Beef patty
· Cheese
· Grilled onion
· Beetroot
· Pineapple slice
· Fried egg [with soft yolk]
· Bacon
· Tomato slice
· Lettuce
· Pickle
· Tomato sauce [or barbecue sauce]
· Optional mayo and/or mustard
In your quote, the phrase is being used idiomatically. The young motorcyclist wasn't just caught for one single traffic offence, such a speeding, for example. Like a hamburger piled high with additional toppings, the boy had other infringements of the law on top of the basic offence - no helmet, no registration, no licence and underage. It's in image of things being piled on top of each other