Exup 1000

The link pipe between caliper sides on the Thunderace blue spot calipers is an airlock / high point in the hydraulics which can be a PITA if trying to bleed normally.
Pump/stop/bleed/pump/stop etc allows entrained air time to do the buoyant thing and rise back up into the link between cycles.
I ...

Stig wrote:wouldn't a thicker head gasket lower the compression?

Or thicker cyl base gasket ?
Check/adjust cam timing if you do either.

Use of the term "gel battery" is akin to calling a motorcycle a "motorbike"and so demonstrates small knowledge.

What you need to choose is a VRLA/AGM [Valve regulated/Absorbed glass mat] battery.

Please feel free to research but otherwise I have studied batteries as part of my employment and also ...

You are just showing off the fancy electrical machinery.
That job can be achieved with nothing more involved than a # 4 thrunging broach and an 2hz flogging peen driven by a half brick bludgeon
I do not exaggerate when I state that I have done this millions of times !

Download an O ring size chart and use verniers to approximate OD and ID and gauge groove width with drill bit shanks.

A kindly old bloke at your local bearing supplier may take you out to the stock shelves if approached politely, that worked for me.

Cost me buggerall and I ended up with many ...

Nobody here has ever before made such a mistake.
You should be deported to New Zealand where such things are normal

Proper hardchrome is different from standard plating and infinitely more durable.
A stone thrown up from the tyre of a vehicle in front will pit the std plating and see you chopping out fork seals, generally regardless of if you try to polish the pit out with diamond paper.
Good hardchrome is ...