Brake lever not returning properly

[florence]

My front brake is being annoying, the lever does not come all the way back when released.   The brake works well and does not at all feel spongey.  My question is whether or not it is worth trying to rebuild the master cylinder, are they serviceable and, if so, are the correct parts available to buy?

Failing that, which are the best aftermarket master cylinders available in people's experience?

[paulbaker1954]

I rebuilt my MS and its pretty easy - I used the DS kit as I wanted to keep the originality.

That said the kit is about the same price as their replacement Master Cylinder but as I said I wanted to maintain originality

https://www.davidsilverspares.co.uk/CB500K0-FOUR-1971/part_41503/

As to not returning properly I am no expert but I wonder if its due to the second TINY hole in the base of the master cylinder being blocked.

Here is a link to my post about this ages ago

http://www.sohc.co.uk/index.php/topic,9625.msg67666.html#msg67666


As a side note the internal circlip (no 18 in the picture) needs some very long nose thin pliers or ideally circlip pliers to get it out as it's well down in the bore

[paulbaker1954]

Have you checked to see if that small piece of rubber tube is still installed?

Hi Ken to what do you refer as I don't have said on mine I think

[florence]

Excellent, thanks, looks like I should get those parts.  The hole looks clear but I will check properly when I take it to pieces.

[paulbaker1954]

Excellent, thanks, looks like I should get those parts.  The hole looks clear but I will check properly when I take it to pieces.

I think if you squeeze lever you can see fluid bleeding back via that hole if its clear

Dumb ? have you checked to ensure nothing simple is causing the lever (rust/whatever) not to return and also lubricated the pivot

[Rob62]

Thats just a cushion to avoid metal to metal contact when the lever returns.. it wont affect the return of the lever. Most bikes don't have one. Its either a pivot/lubrication problem or the master cyl needs a refurb kit.

[florence]

Yes, I will look at the caliper first, I've rebuilt it a dozen times during the past 24 years, it's not designed for the British climate.  Failing that will rebuild the master cylinder.  It's still the original one, never been a problem before.

[florence]

Worth noting that today, I loosened the caliper with a view to taking it off to refurbish.  As sson as I undid the three retaining bolts the brake lever returned to its correct position.  After examination, it seems the caliper is fine, piston moves correctly etc.  I can only assume that when I changed the mudguard, recently, I must have forgotten to adjust the brake caliper upon reassembly.  Now I have put it together and adjusted the caliper correctly it all works fine.

I'm only mentioning this because it shows how important it is to make sure the brake is adjusted after making changes like this.  It's a school boy error and I should have known better.