An ignition ignites the air/fuel mixture in the combustion chamber and although it sounds a relatively simple concept getting it right is extremely difficult. The mixture has to be ignited at exactly the right time in order to give the engine maximum power and in the engine this is measured in degrees of crank rotation before or after that piston hits top dead centre of its stroke. In most cases the mixture is ignited before the piston reaches the top and burns, expands and finally pushes down the piston.
Although this is taking place it is important to ensure that the mixture burns early. It takes time for the mixture to burn and time is something that engines have little of. This is because on high revs for example there is only a few hundredths of a second to burn the fuel. This is why ignition systems have been designed to burn the mixture early and happens as the pistons start on there down stroke.
When a piston is going through a down stroke and passing through the bore it increases the volume of the cylinder and reduce the pressure. This in turn reduces the effect of combustion. Most of the work is done in the early stages of the stroke and provides the power.
The fundamentals described above are created through the use of an ignition and connected spark plugs. Spark plugs as the name suggests create the spark using electricity. This ignites the mixture and starts the process above. Having said that the mixture does not always light due to one of many problems. These include poor compression rations and imbalanced fuel mixtures and goes back to the importance of striking the right balance.
Today ignitions are extremely effective and are generally electric. This gives much greater control and owners should check their spark plugs on a regular basis. Their only downside to modern ignitions is that they often can’t be prepared and have to be replaced. If you also looking at derestricting your moped you will also need to consider how your ignition will work. Consult an expert when doing this.