+1^^^ Take off the front cover(i know it's not a joy) and replace the chain tensioner and guide ASAP cos that's what could happen:
as you see the colour matches with your bit
Thanks guys. The material looks a match, but I'm having difficulty visualizing which bit of the tensioner would have this shape. It seems too narrow and only the one face appears sheared (in this pic, facing up).
I'll maybe get the part in my hand and it'll make sense. Don't look forward to opening the whole thing up. Wonder how much I'll see with just the cover off. I guess that's where I'll start.
Even if you see something from above you'll end up removing the front cover anyway to replace them cos you can't let it there since it started to disintegrate and while you are already there you should replace them both, what i posted is the guide but there is the tensioner there too which can't be in better shape
that's how they look:
So what's involved in getting the front cover off? Does sump need taking off? How much disassembly needed round the top end? How much of a b*gger is the crank pulley?