BINGO! I removed and cleanned out my spark plugs, the falures reduced arround 70%, because I still had some high octanage fuel in the tank. The best to do is spend all the high octanage gas first, and than install brand new spark plugs, or make a very good cleanning on it with a sandpaper number 280 or 600, or even an stailess steel brush.
I'll change mine for iridium later.
To remove the spark plugs it's necessary to remove the fuel tank. Be carefull on this procedure. It is not necessary to drain out the fuel, but how less fuel, the better, because will reduce the tank weight. You'll have a little gas leakage, arround 10ml, when disconnect the tube that brings the gas to the injectors, so put some tow under the plug before disconnect it.
The spark plugs tool is 16mm size and has to be long, because it goes inside the engine head arround 12cm.
I'm not a mechanical, so I can not blame myself for any mistake during this procedure.
If you don't feel comfortable to make it by yourself, please bring the bike for any good service center.
Zachie69, thank you.
Good job for who will try this at home.