Nc30 front master cylinder help please

[fgrant111]

Hi I'm hoping for a bit of advice/ help. I have an issue where my front brakes are binding I have read several of the post on the site and tried most of what has been said to sort the issue but to no avail.
Could some one please tell me how many holes there should be in the cylinder at the point in which the fluid enters from Union of the reservoir?
Just for a bit more info I have done the calliper seals and rebuild the master cylinder which I though was the issue because it had a large amount of crystallised fluid in it. When i rebuilt it i actually fitted the seal nearest the spring the wrong way round however the break was working but wound go soft/ spongy every so often so I took it apart again and noticed the seal so swapped t round, put it back together and now I have the binding issue again.
Hope this is enough info and help would be really appreciated?

[CMSMJ1]

Welcome :)

The usual binding issues we see are caused by aftermarket levers that do not release completely and so get the system all hot and bothered.

So, chekc the levers if they are not the originals

ref the insides of the m/c - dunno I'm afraid! You can get he workshop manuals up in the top right of the forum - doc library. have a look see through that.

[fgrant111]

Thanks CMSM

It not lever thats causing the issue and I have the Haynes manual but that isn't specific enough about the cylinder but I will have a look through the docs u suggested and see if that helps

[Neosophist]

have you overfilled it?

if its too full you can get pressure keepignthebrake on

[fgrant111]

Don't think overfilling is the issue even when I removed only the reservoir there was still to much pressure in the system which leads me to believe it is a problem with a blockage of the holes in the m/c that alow fluid to drain back to the res. I cleaned up one hole and it looks like there could be a second right next to it but to be honest it shred to tell if its just completely blocked or is not actually a hole, can anyone shed some light on this. I'll take it to bit again tonight and try to get some photos up.

[avinitboys]

I had a binding issue awhile ago that took me ages to solve. Did all the usual stuff and then resorted to another set of calipers and spare master cylinder. Still the problem persisted.
It turned out to be the banjo bolt that Hel supplied with my new lines that wasn't quite machined properly. It was seemingly letting fluid one way (under pressure from the master cylinder) and very slowly letting it back overnight. This was made worse the first time I applied the brakes and set a slight bind on the disc. Fluid got hotter and hotter till eventually it would almost seize the wheel! Couldn't for the life of me work out why the following day all seemed well!
Simply changing the banjo bolt cured the problem.
Have you recently put lines on or changed something?

[fgrant111]

That's interesting I'm inclined to say thats probably not the fault due to the fast that the break was operating (although not perfectly) when the m/c piston seal was the incorrect way round, then when I changed it to the correct way the problem appeared again. Also the break was working find then I left the bike to sit for about 2 years and that's when I first had issues and I have not changed the banjo but have cleaned it thoroughly.
Avinitboys From ur experience can u remember if there are two holes in the m/c where the fluid enters from the res. I know It the same question again but i only have one and one that looks like it could/should be a hole so if that is the case then it would make sence that it in not allowing the pressure out of the system when the lever is released due to the blockage. I'm about to take it apart again so pics to follow.

[fgrant111]

Here's a pic of what I'm talking about. By the look of it there should be a small hole on the left where it looks like a small countersunk hole. I would think that this should release the pressure from the m/c but I'm not sure, any thoughts?



Sorry That's the bike in question, here's the mc

[V4beermonster]

Common fault with master cylinders more than likely the tiny hole is blocked it's the relief hole use a fine needle to try and clear it. Fluid will spert out when it's clear

[fgrant111]

Thanks beermonster that was the confirmation I was looking for. So after a safety pin and 2 tiny drill bits I have a hole again. Put the cylinder back together gave the brake a good test then went for a wee run and it seems to be working well! I'll take it out at the weekend, got the MOT booked anyway, and see how it goes before I breath too easy. Thanks very much for all the help.

I case anyone is interested this is the pic after making the hole