Sprocket cover blown off (!)
Out for a (spirited) ride with a good friend today. Heading up some back-roads and I heard and felt a grinding, almost as if the footrest had touched down. (I'm pretty good, but was nowhere near that lean angle.)
Stopped to check, nothing untoward.
Very spirited ride back home, motorway 'speeds', came off into the city, friend waving his arms. Smoke pouring from the front sprocket area, stopped, and the old chain oil set merrily on fire!!!
Took it gingerly home, no sign of any distress, no funny noises, smooth as you like..... curious and curioser!
Got home to take a proper look. Plastic sprocket cover hanging loose, the speedo drive plastic that fits on the sprocket bolt melted, closer look, all the alloy surrounding the sprocket from top bolt to where it comes close to the case casting gone!
Absolutely no chain damage, (brand new DID), anally tensioned to perfection, lubed to within an inch of its life.
ALL I can think is that a stone or some or detritus was picked up by the chain and carried into the sprocket area, to jam solid and crack the alloy.
So, I'm left with a bit of a gap in front of the sprocket, I'd leave it, but the engine will get splattered with chain lube, time to make up a shield and find a way of mounting it securely.
So, there you go. If there is one lesson to learn its that if a chain does snap, it WILL clear off your crank-case so look after your chain!