I've had the head off mine 4 or 5 time , with out pulling the motor.
If there is not enough room then get the dremel out with a sanding drum on it ( or simular) . You will have to leave the center bolt in the top cover while you get wiggle it off, you will see what I'm refering to when you get to it. Just doin't be supprised that one of them woin't come out till you move the top half way off.
I have even un-screwed the long bolts (head bolts) with a pair of vice-grips and then removed the cylinder itself.