Huscvarna 6020 max thread/needle size

[Nj732]

I'm looking at a Huscvarna 6020 for 150 OBO. The bobbin bird nests when the guy tries to sew, I have no idea how to sew neither does he. Does anyone know what the max thread size is and the needle size is for this machine? I am going to be attempting to sew upholstery vinyl/leather with it. this seems to do all right with about 6 layers of vinyl which would be a seam and piping if I decide to put piping on the motorcycle seat I want to make. I couldn't find the chat if there is one so I figured id ask here. im going to look at it this afternoon so any help would be appreciated!