This is a Honda-clone 50cc engine, they're very cool 4-stroke engines. 4 speed with manual clutch, just like a regular bike.
I added an electric motor (brushless) originally with 6kW, 8072 size, now 7kW 80100 size. The motor is the black part below the engine, with wires going to it. It always runs with the ICE-engine, it's connected via a timing belt onto the crankshaft.
(I know, this is unfortunately not able to really go fully electric, because it's always turning the engine) If you take the spark plug out, you can go electric for a few km, but it's intended for acceleration boosts.
The battery is made of high-discharge (45C+) Lipos. It's as small as possible to just provide the 7000W, since it is charged again immediately. It's around 190Wh.
Other than that...on the picture you can see a 120mm water radiator for the electric motor, which I added (the 6kW motor was air cooled). The controller is a VESC (200-300A @16S), but it's only pushing around 100A.
There's an ESP32 microcontroller for the control, I have all the data like temps, currents, voltage etc. on my phone via Bluetooth, and I can change power and charging settings, very similar to any electric motorcycle app.
DerKrawallkeks