Kyriakos.Magdalis

After a long period of inactivity without proper storage, my Raptor 30 v2 TT engine won't start. So, here are the leads:
-Glow plug is new (R4) and the old one is still working (R8).
-The engine just once fired up, raced furiously (luckily the blades were already detached from the rotor) for three seconds and then died.
-The compression is observable, but maybe not strong enough (the flange proofness is questionable).
-The starter has more than enough RPM and the glow plug starter is always charged properly and makes the glow plugs glow yellow, as supposed to.
-The fuel is new, and has a 25% Nitro, which is more than enough.
-The history of the engine is just a litre of fuel.
-The piston shows signs of overheating from the past (dark browny color).
-The fuel runs towards the carb, but only when the muffler if clogged by hand.
-The carb and the interior of the engine is clean and free of residue.

Any ideas on what could go wrong?

Thanks in advance for your attention, people.