Advice on cam chain

Right, Myself and someone else have attempted a big bore kit on my engine but it has had to be raised as the cb150 kit is slightly off and the piston hits the valves, I made a custom gasket to clear this, but the cam chain was under some tension. Having built the engine I went to test it, only to discover after 6min of running the chain snapped!

Annoyed to say the least but I thought it would happen, any idea's what can be done as the chain is being stretched by nearly 3mm each side which is a total stretch of 6mm to the chain in an oval shape.

As I don't think much more can really be done and the temptation of putting the whole engine in the bin has become beyond tempting.

Sorry to hear that :(

You could find out what pitch the chain is and find a new chain that is 2 links longer than your old one which would probably be the easiest solution at this point or get your piston machined down a little so the valves dont hit it, if you had enough patience you could probably just sand the piston down for hours and hours until it's the correct hight.