I ordered parts on internet to fix the engine (new carb jet, gaskets), fortunately I had another piston and cylinder, but I had to clean it. As the moped was temporary not functioning, I took advantage to clean it deeply.
The carb, cleaned with gasoline
I used the same brass jet from a propane blowtorch to fill the choke hole. I just soldered on the small hole with tin solder.
The piston, in very good shape once the carbon removed (soaked in gasoline for 2 days, it came apart easily).
Fresh piston rings.
I also had to adjust the gap of the piston ring. 0.2mm is perfect.
Using a needle file to slowly approach the desired gap.
Test with a thickness gauge, 0.1 should pass easy, 0.2 should pass with a little bit of resistance, and 0.3 shouldn't pass.
The two rings with the same gap.
The rings are set in place.
Rear sprocket cleaned!
I flushed the crankcase several times with gasoline to remove all the brass dust, I moved the connecting rod in case particles were trapped inside the bearings
I checked with a small flashlight, perfect. (the green liquid is 2 stroke oil) I used rubber bands to
secure the connecting to avoid shocks to the aluminium case.
The engine is now waiting for his reassembly, I should receive the gaskets in a couple of days.
See ya and sorry for my English, pretty sure I made a lot of mistakes ;)