Hey,
Just if somebody was in the same point as me. This is the code that I'm currently using.
The template is in Category Articles -> entry. Find:
{record->truncated()|raw}
Replace with:
{{$real_truncated_text=substr($record->truncated(),0,700);}}{$real_truncated_text|raw}
Warning! This is working for me and for my structure with a sidebar. If you are not using a sidebar, maybe you have to increment the 700 to your desired chars number.