Boom furling system maintenance

[Yoya]

Hello everyone
There's a loud sqweek sound coming from somewhere inside the mast when raising the main which is furled on the boom on my 1979 Conway. Not sure if this is the sound of the furling boom mechanism or a sheave inside the mast or what.
How can I lubricate the boom fuller, which has no accessible parts outside of the mast, except for the handle sit on the mast forward side.
I like the boom furling system and would like to keep it working and in good shape
Thank you!