I have just found it in the Qualcast website for download as a .pdf see...
http://www.qualcast.co.uk/manuals/classicpetrol.html
Mark Foweraker, October 2010
www.Fixya.com/Suffolk+Punch+Parts Free Manuals and Support Information about Suffolk Punch Parts
Barry..., February 2010
If this is the black engine with the green covers, the jet adjustment screw is horizontally fixed into the side of the carburettor. Turn it fully in then back out 3/4 of a turn. Also make sure the air cleaner is clean.