Bleeding Brakes - Η αφαίμαξη πεδών

I always like to adjust the levers and seats and things on a motorcycle to suit me, just like when I install an IKEA kitchen to suit me, people with vertically challenging  inferiority syndrome (viz about 99% of the population), cannot reach into the wall cupboards to stash the Tesco pasta bowls.

So when I investigated my K75 for rear brake lever adjustment I discovered that the reason the lever was touching the ground was due to a master cylinder gone to toast.  Whilst the new cylinder was fitted easily enough, bleeding the hydraulic circuit and set up proved more of a challenge, notwithstanding the contradictory and somewhat inadequate information provided in the budding motorcycle mechanics staple bed time reading recipe books of Nigella Haynes and Jamie Clymer.

This heep of shite is the old master cylinder viewed from where the reservoir feed came in - I was trying to figure out how much adjustment I could make to the push rod without blocking the fluid feed port.  I made a wrong assertion initially - I thought that the big hole was the feed hole and I could not understand how fluid entered the hydraulic circuit because that big hole seemed to be in the wrong location compared to the piston.  Obviously the technical literature was useless and wrong.

This is the piston that pushes the hydraulic fluid through the hydraulic circuit when the rod is pushed by the movement of the brake pedal - it is pushed from the left to the right against the return spring (required in a disc brake circuit to relieve pressure when the rod is not pushed anymore).  Hydraulic fluid in virtually incompressible and transmits the applied force through pressure to the brake pads (that provide friction and hence braking effect) .  Air is very compressible and if present in the hydraulic circuit renders the system unable to transmit force as all the work is done compressing the air .  That rubber cup seal on the right is quite clever as it disguises the presence of a one way valve formed by a washer and three small holes drilled in the back of the piston.  This allows pressure to be equalised on both sides of the piston on its return stroke

Here are my tomato plants with fruit - these were irradiated briefly with light from my HID headlamp.

According to this my brake cylinder needed to have  a fluid inlet port (to allow fluid to enter the system to compensate for brake pad wear and the phases of the moon) and a compensating port (for compensating?). It does not seem to show that clever three holed one way valve effort that I discovered during my exhaustive strip down analysis. The feed hole inthe old cylinder turned out to be covered in class A crud and is 0.1mm diameter, very hard to see, compared to the mistaken compensating port diameter of 1.5mm.

My other ride is boxer powered by means of  two well proportioned jugs sticking out either side.

The fraudulently named Eezi-bleed -  a pressure bleeding system that did not  purge all the air from my K75's devilish rear brake hydraulic circuit.

The newly acquired vacuum bleeding system in action - bleeding can be fun especially..

..when a little bubble appears from the ABS unit.

Epilogue:  if at first you fail rush out and buy more tools.  Bananas are a natural source of goodness and I'm going on a tour of Southern Greece tomorrow with "boxer power". It turns out that the Engineer who designed the master cylinder adapted the design from a sequencing valve used in the peroxide secondary pump fuel line in the V2 rocket that comes into play during the rocket motor start up sequence.

======================================================================================

************************************NEWSFLASH***************************************

Further to the kind expressions of care conveyed by my worthy correspondents, I have trawled through the attic and found an  efficacious present given to me by Mrs Nikos during our early courtship.  The only hitch is that this inflatable banana protection sheath (IBS) was scaled for the Japanese market.