As mentioned above you dont need any parts for a HC overhaul.davethewheel wrote:i wouldn't mind having a go at serving the existing one as i'm sure it's probably just blocked up with crud, can anyone explain how to do this and are there any parts available that i will need
The job is very much like overhauling a carburettor : several small and delicate bits of which location and orientation must be closely observed.
Start job by a good external cleaning using a stiff brush with engine cleaner (or petrol).
You will soon discover that both rubber prtector caps are easy to remove. Leave the ball hook on the protruding axle. Its a swine to remove and the protector cap folds over nicely anyway.
Now the end membranes are revealed. Make a scratch mark on HC body to identfy the ballhook end
Carefully by working all around the circumference prise off the retainer rings from the rubber membranes
Then remove the exposed nut and washer and dismantle further from here, taking extreme care of the thin steel dishes - and note how everything fits.
When ready - pull away the piston axle by the ballhook.
If it binds then turn it side to side while pulling - using gentle violence.
The ballhook ended piston rod may be pitted at ends near the housing ends - making the piston stick in the bore. This is of no big concern as there is no sealing valve functon here. Only a surface helping the piston to slide squarely and precisely.
However if the piston rod is pitted at the middle section where the sealing valve function exist - you dont need go any further. Discard this HC !
Clean everything using cleaner/petrol then wipe/blow it dry and IMMEDIATELY immerse parts in a jar wth clean LHM.
If not - the parts wil start staining rather fast. (not the HC alu housing though)
With extreme care rub down any pitting on the end(s) of the piston rod to make it slide nicely (wet) in the bore.
There is a tiny special cap in an off center bore in the HC housing. The cap can be removed using a bolt matching the bore diameter and hacksawing a slit in the bolt end. This will reveal a bunch of tiny micro bore dishes with distance spacers that also needs cleaning.
Re-assembly is a rever...
The rubber protectors, membranes and membrane steel retainer rings are the only bits available as spares for the HC - all models.
The HC itself w/o the bracket etc. is available as spare for the BX.