Ok, here is the latest news about my GMS. Today I did more testing with ethanol and caster oil as lubricant. I was getting good result and after about 10 mins, the engine stopped with a clicking sound. I noticed compression was lost so I know something went wrong. Tool the engine apart and noticed the piston ring broke. Luckily no damage to cylinder. The broken piece ended up in the crank area.

Question to those expert, what could have caused the ring to break? Not enough lubricant or ????

Borna