Overhauling front master cylinder...

Dee · Post by **Dee** » Wed Oct 04, 2006 10:57 am

...Is what I may well be spending Sunday doing (weather depending), at the same time as replacing the old knackered brake lines with braided stainless.

I'm a fairly competent mechanic, but I've never overhauled the master cylinder before (the kit looks straightforward enough), so I'd appreciate it if anyone has any tips/things to look out for.

Cheers, y'all.

Post by **phuk72** » Wed Oct 04, 2006 11:40 am

why does it need an overhaul?

Dee · Post by **Dee** » Wed Oct 04, 2006 3:20 pm

Where do I start?!

The front brake is utter crap; very spongy indeed, but having checked several times there's definitely no air in the system. It seems to be an intermittent problem, too - more often than not the front brake is awful - I can bring the lever practically into the bar. Sometimes, however, the brake is great (for about 2 squeezes of the lever before going back to normal).

Also, despite the brake fluid being changed, dirt is appearing in the clean fluid in the reservoir when I pull the brake lever.

To be honest, I was just going to swap the hoses out for the braided stainless, but the other half suggested that my master cylinder might be a bit knackered too, so I've picked up an overhaul kit.

jpe · Post by **jpe** » Wed Oct 04, 2006 3:39 pm

Dee wrote:It seems to be an intermittent problem, too - more often than not the front brake is awful - I can bring the lever practically into the bar. Sometimes, however, the brake is great (for about 2 squeezes of the lever before going back to normal).

I made the swap to braided lines on my t-rex and suddely it developed similar problems to what you're telling us. The brake would work for short braking, say on the track or hard braking on the motorway. In town doing "teddybear" braking, squeezing the lever for longer period than 2 sec it would start to sink towards the handle.

U could then hold it to the bar with no braking at all after say 10 sec,

but releasing it and squeeze again and it would brake. For the first 2 sec's...

Turned out the head cylinder couldn't keep the pressure up and the fluid leaked back to the reservoir after the first initial squeeze.

I simply swapped to R1 bluespots complete with head cylinder at that point...

Dee · Post by **Dee** » Wed Oct 04, 2006 3:49 pm

I simply swapped to R1 bluespots

To be honest, that's my next purchase (when I can afford it)

Post by **phuk72** » Wed Oct 04, 2006 7:39 pm

Have fun!

Blue spots and braided hoses are the way to go (and an R6 mc makes a load of difference as well)