After 10 minutes riding, it gave out a tat tat at noise then it lost power and would not start again. When I try to turn the engine it gives a clanking mechanical noise. It has done only 12000 miles. There is oil in the engine. Can anyone suggest anything. Thanks

only an engine strip will tell i'm afraid

Take the plug out, do you have compression?

Take the head off is there a piston and what does it look like?

Take the barrel off is there a con rod?

You can work it out from there on your own I expect.

No simple answer other than what AIRHEAD suggests, your just gonna have to get your hands dirty/oily.

P.S. not taking the piss, this is just the wonderful world of motorcycling.