Thanks for your informative reply Andy.

Carried out a leak down test and it wouldn’t hold any pressure at all. Switched the pump from left to right and still the same. Now suspecting my seal has gone.

Watched some Japanese videos on you tube where they pour a mixture of fuel and 2T oil into the left reed inlet or down the left crankcase with the cylinder off to check if it seeps to the other side?

Any issues with doing that?