Can anyone post some pictures on how the seat is mounted on the 1980 TL320? 

Here's some pics for you.

Is it metal or plastic tank. the fitting of them is different. my 180 is metal, but yours could have been altered.

My tank is plastic.

My bike is a later 1980, has plastic tank and Betor forks.

should be like the pictures above then.

  Here is what I have. Looks like I have everything except the rubber straps in the back. I'm not sure what mounts the seat/tank to the hole in the frame. I know the rod with the rubber washer goes through it but what holds it? Thanks 

In my picture above, the second one, I show the sprung loaded, sliding latch from below. Looks like its missing on your frame.

At the top the spring and at the bottom the tab to operate it. Not really as clear as it could be.

  Is this on a bracket that screws to the frame or is it welded? Can you post another picture? Thanks 

I will have to get the straps.

Edited July 11, 20179 yr by dozerash

Here you go.

looks like you have a bracket that the spring catch slides into welded to your frame. Mine doesn't look like it ever had anything welded to it.

All three of mine are the same. Maybe yours had a metal tank originally. The fixings for those are different. Don't ask me how they differ as I have never seen one to be able to compare.

  I got a hold of Martin from Motoswm and he said my bike probably originally had a metal tank. 

 I probably can make something to work.