Rear Brake has no pressure

[westy66]

Hi Everyone,

My rear brake doesn't seem to want to work no matter how much I bleed it!

It's almost as if the seals have gone in the piston attached to the rear brake lever/pedal.

Does anyone have a diagram or has anyone come across this before?

Thanks,

Westy

[fallenmikethebike]

I would have thought if the seals had expired in the master cylinder , you would see fluid leaking back past the seals ,and onto the pivot /adjuster .
Do you have the means to reverse bleed the system? this sometimes gives a pedal where other means have failed .
Is it that you cannot get any pressure at the pedal at all ?
I personally do not like those self bleed kits , and much prefer the old manual process of pedal down , open valve /then close valve / then pedal up ,with fluid going into a clear jar ,ABOVE the height of the slave and master cylinders , ect ect .
What led to current situation of no brake pressure ?

[westy66]

I was out on the trail and eventually the back brake stopped working - i can see no leaks at all!

If I pump the pedal I can get a bit of pressure but by applying a nominal amount of force the lever slowly goes down and reaches its full travel. It seems like something is leaking past the piston inside the master cylinder.

I'd love a diagram if anyone has one.

Can I buy a seal kit from Leisuretrail?

Westy

[fallenmikethebike]

It could be seal , or a scratched bore in the master cylinder, only a strip down will reveal the answer .
If you are going to pull the system apart you may ,with a decent vernier be able to source the relevant seals from an on line store [ weemoto ] ect. LT will almost certainly have them in stock if you can't be 'rsed to measure and source them .
Sorry i don't have diagram in my limited workshop manual that shows the master cylinder .
They are generally self explanatory when pulled apart , push rod , cir clip , seal and block .
New washer's are always a good idea , when rebuilding .

[pmac]

Hi Westy
My CRM had a similar problem when I got it, no pressure at caliper, and no sign of leaks. When I took it apart I found the plunger in the master cylinder had stuck in the brake on position at the top of the cylinder, so it would not pump any fluid to the caliper, but the brake lever would still return, because of the springs on the lever and brake light switch.
It was quite easy to repair, on the back of the master cylinder there is an angled plastic nipple that goes to the fluid reservoir. This is held on by a circlip, if you remove this you can see into the cylinder without taking the whole thing apart, you can then free up the plunger through the hole, and hopfully this will cure the problem, you will then have to put it back together and bleed it.
Hope this helps

pmac.

[westy66]

Thanks for all the help guys, I just phoned LT and the seal kit is £46 !!!!

I think I'll try pmac's suggestion first.

[keithl8187]

Thanks for all the help guys, I just phoned LT and the seal kit is £46 !!!!

I think I'll try pmac's suggestion first.

Let us know how you get on westy66.

I have a similar problem but with brake fluid leaking from master cylinder. Stripped it and the seals are split. Couldn't believe the £46 quid LT want for the seal kit, although it does contain piston, seals, spring, circlip etc.

Looks like I'll be searching local bike shops for something that fits, unless there's somebody out there who already knows what else will fit.

If I find a cheap solution I'll post it.

Thanks, Keith

[Furnuts]

just replace the entire master cylinder with one off a cr 250 i imagine it cant be that hard of a fit

[knackeredMk1]

CR, XR, CRF,......................... Just be careful and look before you buy. Most off road bikes use the same Nissin mastercylinder with/without fluid reservoir built in.

My project has one built in - from a CRF450.

[westy66]

Hi Chaps,

I've managed to find one off an AR that (as you might expect) fits.

The £46 for a seal kit is too steep really, otherwise I would have bought the kit - my fix cost £20 + p&p for the whole lot.

If the kit is the same as the XR, CR or another Honda why do LT continue to mark them up so much. it just makes me suspicious next time I ask for a price from them - shame really as they seem quite decent chaps!

No one likes being taken for a mug do they!

[westy66]

If LT put sensible mark ups on the bits they'd probably sell twice as much than before and might pick up XR and CR users as well. Mind you lower margins and twice the effort .... maybe not!

[knackeredMk1]

I suspect if you asked for a genuine Honda seal kit for a CR or XR it would cost pretty much the same from a Honda dealer. Exception might be Lings or David Silver Spares who are volume spares dealers.

[keithl8187]

Sorted

Local bike shop BJ Bikes at Doctors Piece in Willenhall have replacement sets including piston, seals, spring, circlip and dust cover for just £17.50. They don't sell bikes but have spares for just about anything.

Fitted a treat in about 10 mins.

Keith