The real reason they take the key is to secure a bargaining tool. The policeman will tell his victim that their key will only be returned after they have attended a court case. This is generally a bluff designed to create a panic payment. Beat the policeman to the punch. As soon as you are pulled over take the key out of the ignition and place it in your pocket. Policemen in Bali have the eyesight of predators. They are always watching for wallets brimming with tourist dollars and euro's. Anyone riding a scooter should always carry a small amount of cash separate pocket. They should then pull this money out while telling the policeman it is the only cash they possess. You can’t give what you don’t have.
Make sure that the cash you have for fines is in small denominations. And be visible handing it over. The policeman won’t want to be seen counting the money. And it is easy to fool them into thinking that they are receiving a larger amount than they are actually getting. It is always wise to be polite to any policeman that stops you in Bali. Indonesians do not like to lose face. And policemen in Bali expect to be treated with a certain level of respect. Address a Balinese policeman as Pak or sir and always smile. It will go a long way to reducing your fine. If you are pulled over you may be threatened with court, a large fine or confiscation of the vehicle. It is important to remember that in Bali most problems can be solved with the transference of cash. Remain calm, non-confrontational and remember it’s all about the money. (50.000rp will be enough.)
You will see a number of locals riding without helmets. If you are a tourist in Bali the same rules do not apply. Policemen in Bali love nothing more than pulling over tourists without helmets. Policemen in Bali do not move around a lot. And Bali has a rabbit warren of small roads that lead to the place you are heading. Make a mental note of where the police are stationed. Then use the back roads and alleys to get to your destination.
Solve all problems by purchasing an international driver’s license in your home country. They are not expensive and they are recognized. An international driver’s license will save you a great deal of hassle and cash. And remember, use always a helmet!