OK.....
I had a fiddle with things, made up new fuel lines, set fuel levels and went for a short squirt....goes great, I am going to Kilcoy tomorrow so more after that.
it seems that the fuel in the airbox resulted from a leak in the fuel line....
Using the XJR 1200 settings I have set the fuel level at 5mm below....
The float level measurement varied wildly to achieve this 5mm...I haven't ever measured the fuel levels before - I guess I have been lucky as the machine never had a problem before these BS36 units
Thanks Xtian for urging me to do so....
I havent changed the jets or needles but I suspect I may raise the needles tomorrow after a run...
thanks for the advice fellows...