Got the feeling that it was about time the Yamaha got its annnual bath and polish.
So I stripped it down completely, left the chassis and slides to soak in a large bowl of hot soapy water for a couple of hours and set to cleaning up the valves and water keys.
Not finished yet, but I'd brushed through the tubes and done with the water so I emptied the bowl. I don't normally get too much gunge coming out, but on this occasion one of the scoops came up with a rather impressive but quite dead bush cricket.
Could have been worse I suppose. I wouldn't want to find the remains of one of our resident wall geckos in there.