I still have my K Rapid but it's been off the road for about a year now.   it failed an mot last September for emissions so Saturday I stripped down the carbs, checked the jets for crud and had a go at balancing the throttle butterflies.  The battery was dead so after overnight charging it was ready for action on Monday with new oil and filter too.

 

Started quickly after carb floats had filled and after some further fiddling with a rather cheap carb balancer, it idles much better than it use to and a short drive around the estate indicated it was running really quite well.   I even got the Gunsens colour tune spark plug gadget out to see what a couple of cylinders were running like.   Nice blue burn at idle and low revs with a bit of orange creeping in at higher revs.   I'm hoping that the mot emissions check at 2000rpm will be fine on the back of this.

 

This is all very well but the short drive around the houses identified I have no brakes to speak of.   Handbrake work fine and there was no evidence of fluid loss at any of the four corners and the master cylinder doesn't appear to be leaking (unlike the clutch master cylinder which I replaced last year). So after a prolonged lay up do I just need a simple bleed of the system with fresh fluid or is the master cylinder a potential problem.   There is no pedal pressure and it pretty much goes to the floor.  There is some retardation but when it takes several metres to stop at 10 mph, it's not going anywhere near an mot just yet. 

 

Any guidance appreciated.

 

 

It might just need bled but the seals on the master cylinders can go on them (like any old car) - so you don't lose fluid they just don't push any fluid round the system

I would make sure the cylinders in your rear drums aren't leaking also.

Clamp all the brake hoses. If the pedal is still poor there is most likely a fault with the master cylinder. If the pedal is good with the hoses clamped release each hose clamp one at a time to work out which corner your problem is at.

Thanks all for your advice.   Hoping the rear cylinders are OK as these are replaced about three years ago.  As brake bleeding is a bit of a faff for one person without an assistant,  it's gone to my local garage I use for mots and the like this morning for them to check things out.  I will report back.

Turns out the rear drum cylinders were seized.  Replaced and system bled, we now have brakes.  Mot on Monday.