Is there any reason why my petrol over flow pipe pisses out petrol for no apparent reason? its constant until turn petrol off???

Try tapping the side of the carb with a hammer or mallet. BUT GENTLY.

It's your float valve getting stuck. You will need to clean the carb out if it continues.

cheers mate, i'll give it a go tomorrow too dickie dark at min :) thankyou :) so glad i joined this site.

I had a bike what did that as far as I can remeber it was the foalts in the carb and the float valve that was sticking open and letting fuel out every were

I've heard people use a SMALL SPANNER to tap the carb, as knackered said.

It's more than likely that the fuel inlet valve will never have been changed, so it could well be worn, but yes initially, as has been suggested, a gentle tapping of the float bowl, though I tend to recommend the blunt end of a medium weight screw driver.
Mike

or just remove the carb, clean and check the jets, check float level there is a diy way if you google it then re-fit carb turn petrol on start engine no overflow problem jobs a goodun

agree with john above