nc30 Brake Problems

[twistywizard]

We were out for a ride last Sunday, missus was riding the NC30. Part way along she pulled over with problems. The brake lever just went soft and touched the bar and offered little braking power. We managed to adjust it and it works and stops fine however needed to be pulled literally to the bar.

Obviously not right! It has been fine and recently had some Braided hoses from Graeme along with new pads and a complete bleed through with a vacuum bleeder! Anyone shed any light on what it may be? Knackered master cylinder perhaps?

Bad VFR

[The Hamster]

As far as I can see, there can only be two options here..

Air/Foreign Substance in your brake fluid making it go spongy...
or..
As you suggest, a Knackered Master cyclinder, which also wont help the other point above.


If all your hoses are fairly new and fine, your pads are ok, your caliper seals and pistons seem ok then there really is nothing else it could be!!!!




I would suggest bleeding clean fluid through the whole system, then draining it and re-bleeding more fresh fluid in just to be on the safe side. (I have a halfords trade card which means I get a litre of brake fluid for GBP 1.92p. Hardly making expensive to waste a bit here and there.)
If this doesnt solve your problem, its Master Cylinder Rebuild/Replace time im afraid.

[wullvfr]

as he said!!!!!

because you had new lines fitted recently and bled properly using the vacuum method then i would be inclined to say your m/c is goosed.

it's awfully quick for the lines to be full of air so badly that the lever becomes so spongy it's travelling all the way back to the bar.

im sure i have a m/c kicking about surplus to requirements..........£10 delivered.



wull

[twistywizard]

Cheers guys this is what I thought. I would be surprised if it was an air leak as it was literally instant. She did well to be honest we were going along at about 60-70mph when it happend she was surrounded by cars and only passed her test a month ago and only had a back brake to stop.

I will get it bled through again as it wont cost anything. If this yields no joy then I will take you up on that offer wull!

Would a master cylinder from a GSXR 750 K2 be any use? I have one hanging round from when I swapped to a Brembo. Wonder if it would be a half decent upgrade?

[Growler]

reading this with interest as I stripped the brakes off my project today. The bike had sat for almost 3 years untouched so you can imagine the state of the calipers etc. Before stripping down the lever was spongy and did come back virtually to bar. After stripping and rebuilding/ bleeding couldn't get any pressure worth speaking of in lever. I'm think master cylinders shot but wondered if there's any way of testing it to be sure? Tried putting finger over outlet where banjo bolts attach and squeezing lever. Little if any pressure to speak of? Is this normal? I had expected my finger to be pushed of with force as the lever was pulled? Thinkin of an over haul kit now for master cylinder on ebay but I surely only need the rubber seals and not the rest of the internals? Any advice would also be appreciated as I appear to have a very similar prob to twistswizard..

[Neosophist]

Another possible option that I don't think has been mentioned is that you have a leak somewhere which is letting air into the systme as the brakes are being used, maybe a loose banjo or knackered washer?

If you cabletie the brake lever on overnight have a look for weeping fluid from all of the joins (theres not many!) the next morning!

[twistywizard]

Another possible option that I don't think has been mentioned is that you have a leak somewhere which is letting air into the systme as the brakes are being used, maybe a loose banjo or knackered washer?

If you cabletie the brake lever on overnight have a look for weeping fluid from all of the joins (theres not many!) the next morning!

Did that yesterday no difference and leaks. No knackered washer EVERYTHING was brand new.

Will try a new Master Cylinder and go from there

[Le_Blur]

I had a very similar problem with my brakes. Having rebuilt both calipers (except for new pistons), rebuilt the master cylinder, installed braided lines, fitted new pads, and bled it until the cows came home the lever would still alternate between being totally locked out to being able to pull it back to the bar. A friend of mine who worked for Honda insisted the cheap and nasty aftermarket lever the bike came with was the problem. Turns out after replacing it, the aftermarket lever had a totally different pivot point and was not allowing itself to return fully. We also tried filing the aftermarket lever to insure it wasn't snagging in the clamp. Sounds wierd, but everything worked perfectly after changing it.