popped two engines in three weeks!!!

[Fish]

hey guys i have a nc30 i recently put in a second engine in cause the previous engine
had a bearing knock.
3 days after puting in the engine i pick up bearing knock so i send it back to
the workshop puts in another engine and after 3 days of which i only rode the bike 2 hours
the engine picks another big engine knock ,im lik WTF!!!!
is this a common prob ??? i thort these engines were bullet proof
bike is stock

[CRM]

Unlucky, they are tough engines. however your not buying engines from some wingnut that likes to wheelie are you ? thats a sure fire way to say tatty bye to your big ends very quickly