Tsdz2 clonking noise

Hi,
I have a bike with Tsdz2 engine that I have been using happily for 2 years. Now it just started making noise. It is some sort of "clonking" noise that comes about 10 times each revolution of the pedals (when pedaling rapidly the "clonk" repeats at a hi rate and when pedaling slower it repeats at slower rate). Also the noise appears only after while, when I have been riding for about 2-3 kilometers the noise starts and stays until i stop riding. The next time I use the bike again it is free from noise the first 2-3 kilometers then it starts.

Anybody know what is causing the noise and what to do to repair it?

Thanks

Sorry I have nothing specific to add, but first stop should be checking everything is tight. This weekend I thought something bad was happening to mine - a new clunk when starting, stopping, and to some extent during pedaling.

I found that my lockring had come loose (and I don't use the anti-rotation clamp, but instead just have the motor shell braced against the frame).

Anyway, I hope it was something that simple for you.