Certainly something mechanical inside that cylinder, either a valve(s) failure to seat as you mention, hole in the piston, broken wrist pin or something similar. It is possible althugh probably unlikely, that a valve has a piece of carbon or other debris under the seat. At any rate, I doubt this is repairable without taking the engine apart, and I do not believe that can happen until the engine is removed from the bike. Sorry to hear this piece of news....
I do not know if you can make it work out financially but now that these bikes have been around for quite a while, there is always the possibility of finding a good or even great condition engine in a bike that was wrecked. ? Not sure what that would cost you in Venezuela, and I am not sure it would be cost- effective given the large amount of labor that it would take to swap engines.
The very best of luck going forward though either with that bike or if not, then hopefully with a nice replacement bike at a reasonable price.
Brian
Edited to fix country the OP actually lives in.
As you can see in the picture (No.1), cylinder one has not admission at all.
That look as a valve problem, but then i decided to clean the
gas bump. After that, the bike was much better (No.2) .
I did the same test, two hours after and the problem persist
with the same cilynder (No.3).
Definitly, IMO the bike has a stuck or burnt valve.