Thank you for the fast replies, I would say its had no more than 5 hours run time. I keep my engine and car very clean ie, after run oil and clean the car after every run and i always use quality fuel.
This time i was out on the street, i have never raced or thrashed the engine.
The piston is now very tight in the sleeve.
I spoke to Kyosho and they say it is from over revving.
All the bearings seem to be ok.
Im now at the stage where im thinking of buying another engine such as Hpi or novarossi etc.