Front Brake problems on 1999 Dominator

[Manx James]

Hello

I bought a 99 Dominator a couple of months back, It's been great until last week when the front brake just stopped working. The lever comes right the way into the bar with no resistance and no braking effect at all. The pads are ok, there is no sign of fluid leaking and the reservoir is full. I bled the system but it didn't fix it so I though that the problem must lie in the master cylinder. I replaced the piston and seals in the the master cylinder (nearly £50 !!! with P&P and VAT) but it still doesn't work. With a full reservoir and the brake pipe removed the fluid should squirt out when the lever is pulled, but nothing happens. I've checked and re-checked that everything is fitted correctly and yet it still doesn't work.

Does anyone have any ideas or had a similar problem in the past ?
James

[switch]

Try bleeding with a professional vacuum pump. You probably pulled in some air in the wrong place. Doesn't happen unless the gaskets in the master cylinder are worn or the cylinder is subjected to a direct shock.

The symptom for the above would be a lever that feels light as a feather with the brake not working at all.

[catteeclan]

Also if you've still got the rubber flexi pipes on, clamp it close to the master cylinder and see if the lever improves.

[allanmac]

I take it the piston that the lever pushes against is intact on the master cylinder?
Cheers allan

[pogo]

Hi.I had exactly the same problem with my FX 650. There is a tiny pinhole in the master cylinder which allow the next influx of fluid when the lever is being pulled.This gets blocked so that you can squirt out a little fluid when the bleed valve is open,but the reservoir doesn't refill quick enough for the next squirt.Make sense?
Take out the piston and seal again,and looking into the reservoir from the top,you will have to find the hole,and unblock it with some fine wire or air gun.
I was lucky that many years ago I had the same problem with a car,so had an idea of where to start looking for this problem.
I hope it sorts the problem out for you.
Pogo

[Manx James]

Thanks to all of you for your advice. I've tried everything you all suggested and a few other things. So far the bike has had
1 - new piston and seals fitted in the master cylinder
2 - brake hose

I eventually took the bike to a bike shop/garage (ex TT racer Paul Dedman in the IOM) who was confident that he could fix it. It cost me £100 and is no better. Dedman reckons that the master cylinder is worn, I can't see how this can be the case as the piston seals are rubber, there is nothing hard contacting the inside of the cylinder. He also reckoned that the brand new hose was in poor condition and that the front disk is badly worn - all of which is nonsense. Dedman also fitted new brake pads (not that there was anything wrong with the old ones) none of the advice or help has solved the brake problem.

I've clamped the hose and when I do this the brake lever is solid so I'm pretty sure that the lever/Master cylinder/ Piston/seals and hose are ok.

The last thing to change is the caliper - I'm reluctant to buy a new caliper without being sure that this is what the problem is.

Any help much appreciated

Frustrated and confused

James

[mad4it028]

clamp the hose near the caliper if it goes harder then the master cylinder and the hose are good leaves only the caliper

[Manx James]

That's what I thought, I've clamped it at the top and the bottom and it's solid.

Any one got a working caliper for sale ?

[switch]

Brembo. Bleh. Got a working Nissin brake setup laying around the workshop.

Now for the bad news.

The caliper and master cylinder for Nissin/Brembo brake setups isn't guaranteed to be compatible. I.e. you might need the whole system.

The brake pads are different. Not an issue as the pads on my setup were only used a short time before the camshaft gave out. Consider it a bonus, but remember to brake the pads in throughly in case you use them - this goes for any second hand pads.

Also, while the setup (cylinder + hose + caliper) does work (does so well, too) and doesn't leak at all, the lever's pretty spongy. If used, you might want to replace the existing orings in the caliper pistons and brake cylinder. I know for a fact that this improves the lever from fully spongy to fully stiff in one go. Repair kits go for like 20euro around here for each component and a braided hose goes for about 25e. With a front brake system going for 75e, that's 140e for a fully functional, good as new braking system. I don't really like hearing that you spent 100quid (~120e?) without even fixing the problem

...that and I'm half a continent away.



You could try ebay tough. I know of a few dealers in Germany that break dommies for parts; got a headlight, swingarm and other minor stuff from them (including a charging regulator that's better than my own).

[StumpyFingers]

It is possible that the Caliper has seized. I had one go and it stuck on.