The Ilford Sporti six that I got this already exposed film from, I put a roll of HP5+ through it and got nothing out of it. So I put it on a shelf. And then I realized whilst tinkering with the newer Sporti 4 what a dramatic effect a wee bit of WD40 could have. So I got it off the shelf and began tinkering.
It's a bit less primitive than the other Sportis, and most of the shutter mechanism cannot be got at because it's moulded into the bakelite lens housing. However, I managed to dab some WD40 onto the back of the shutter, and it trickled down and stopped it from sticking open - which it had been doing. However, it still stick open when the camera's upside down, which enabled me to clean the inside of the lens (with a damp low fibre cloth on the handle end of a paintbrush.
Test roll's in now. We'll see.