Pigford wrote:I did have a 180 shim - but lent it out a few years back and not seen it since

If tips of valves need trimming - I believe its a max of 0.3mm
Piggy you are spot on the money
If you still are too tight then you'll have to have new seat fitted

This must only be performed by a really good engineer, as a bodger could write off the head and they are no longer plentiful!
Ralph Ferrand
Z1000A1 (1977), Z1300A5 (1983), Z900A4 (1976) GPZ1100 Unitrak (1983)(project), RD250B (1975)(project), ZRX1200R (2005) DT175MX (1981) YZF R6 (1999)
http://www.bikerstoolbox.co.uk