Thank you very much guys. I read your advices very carefully and after that I have discussed with my friend. He is an old biker and has some experience.
My friend told me that he already check and all 4 pistons are running, he clean and inspect the carbs 2 times, including the diaphragm and all is in OK condition. Compresion were not done, maybe next step. I told him about the boots, he said are in good condition. I asked him to inspect the diaphragms one more time with a lot more attention, maybe a very small crack, difficult to observe.
In the 1st, 2nd and 3rd gear, the engine has power, but when he shifts to 4th gear and specialy to 5th gear, the bike cannot accelerate more, even going slover.
The cruise control were removed and I don't know if it were done correctly. Can be the cruise control the culprit ? or can have any influence ? as the cruise control has some electronic components ... maybe some wires disconnected or cutted ..
Thanks
Marcel