AVL 500 engine weak spots:
1. Sprag clutch prone to fail, probably the best-known thing to go wrong;
2. Big end failures, particularly on early models shipped to the UK. mostly down to the hardening failing on the crankpins. Can spray the inside of the engine with highly abrasive metal particles when it happens;
3. This is what Bilgemaster was probably thinking of, the feet can snap off the tappets, which for some reason were designed to have thinner spindles than the iron barrel engine tappets.
Still went ahead and bought another one last week, as a learner bike for my wife.
A.