Many owners of Alpha or Delta mopeds want to do a bit of tuning, not just on the outside but, as they say, "at heart" — that is, to somehow improve how the moped performs and boost its acceleration and speed. It's no coincidence that the word "tuning" means "setting up". And that setting up is what we'll talk about. You don't always feel like digging into the engine and replacing the moped's cylinder and piston kit, because there's nothing wrong with it. The moped starts well and rides decently too, for its size, as they say. You don't want to take apart a well-run-in piston kit. And then we remember that, apart from engine displacement, speed and acceleration don't depend on the cylinder and piston assembly alone. Things like the carburetor and the ignition, or more precisely the CDI unit, are far from the least important parts. So let's talk about the CDI unit.
For the engine to have good throttle response, and to run at all, the air-fuel mixture must be ignited at a certain moment, roughly 2.5–3 mm before the piston reaches top dead center. This is exactly what the stock CDI unit is designed for. With this advance, the optimal engine speed is in the mid range, roughly from 2 to 5 thousand rpm. At these revs the engine delivers maximum torque and fuel economy.
As the revs rise, the engine sounds like it's straining to the limit: it keeps gaining revs, but noticeably more weakly, until it hits the 8 thousand mark. And fuel consumption at these revs far exceeds the claimed 2 L/100 km. The explanation is simple: at such revs the mixture needs to be ignited even earlier, for example 4 mm before TDC, otherwise it simply doesn't have time to burn completely, so the combustion energy isn't fully taken up by the piston and simply flies out the exhaust through the already open exhaust valve.
On the other hand, if the advance is permanently set that early, the engine will run unevenly at idle and mid revs, overheat and possibly backfire into the carburetor. That's why you need a so-called ignition advance module, a device that varies the ignition timing. More precisely, you need a CDI unit with such an advance module built in. These CDI units are called sport, tuning and so on. But there are no such CDI units for Alpha mopeds, or they are very rare.
So some owners of these mopeds, who have some know-how and a circuit diagram, build such a CDI unit themselves. But what if you know nothing about electronics? You can take a tuning CDI unit for a 4T Chinese scooter; luckily, there are plenty of them, in many different models. Connecting it will take some work, but otherwise they fit perfectly, because the generators on these scooters put out the same parameters as the generator of an Alpha or Delta moped.
In use, this CDI unit has performed well: the engine revs up more eagerly, accelerates harder, and the CDI doesn't get hot. All in all, it's a good fit for light tuning, so if you want, you can just resolder the connector and you're done.