Engine drain
We first did several races to allow the oil to heat up and be more fluid. Then we unscrewed the drain plug which we connected with a hose to a tank (can)

It took about 45 minutes for the oil to completely evacuate

refitting the drain plug, opening the filler cover, filling with the appropriate oil

we did several races so that the engine soaked up the new oil well

we noticed that the old oil was filled with iron filings

then we did some conclusive tests, restart ok