Have overfilled reserve tank with coolant, should I siphon some off or is it ok to leave about the upper level ?
About the upper level or way over it? Ideally somewhere between the 2 marks,siphon some out to be safe.
Should be measured when bikes level. Think 2cm over when on stand would be more if it was level. Not sure exactly what would happen if you left it but I guess the chance of hot fluid squirting out is best avoided.
Would take a bit out, last thing you want is coolant coming out of the overflow pipe mid turn and going over your tyre