I have now discovered that the light (1.2kg) yellow sealed Motobatt MBTX4U batteries, that I used with no problem at all on my B class carb. bikes last year, do not have the output to start & run the A class bike with the extra draw.
Therefore I have, perfect for B class bikes:
1 x brand new in the box Motobatt MBTX4U battery (one week old) - £20 1 x only done two race meetings Motobatt MBTX4U battery - £15
Hard lessons learnt from a number of years racing, has resulted in a general rule that I am allowed to touch the bike and spanners, however, NOT at the same time...
As "we" are building up a Guzzi for the Classic TT now, and "we" will need to work out how to do 120 odd miles without a charging system... I have already robbed the ridiculously expensive Lithium Shorai battery that has the weight of a gnats nob off the Guzzi racer and onto my 620, I am an idiot...