ETZ leaking Brake Master Cylinder.

[Puffs]

Note the construction is different, but to me those washers look like copper.

[nice2day]

Great info as usual Puffs, yep they do look like copper. Dowty washers are steel on the outer circumference.
I think I'll give it a try then as long as I actually do have a tight fitting copper washer...Will report back when done (in a few days). So I will get back to the seller and accept the unit as long as it doesn't leak. Having said that I still would like to see other similar replica units to make sure NONE of them have the "cone" type seal as I am still suspicious the one I have has simply been drilled too deep and removed the bottom sealing cone shape.
Much obliged Puffs.

Les

[Blurredman]

The original has the angled connection internally. This is what the pipe normally buts up against- There is therefore space between the end of the hex connection and the master cylinder/caliper.

This is the way hydraulics should work, it's one of the reason we flare the ends of the pipe/cables- Not only does it stop the pipe simply coming out (if it is a pipe) from the connection fitting but it also acts as the seal itself- Crushing down between the pipe connector and the cone shape as you put it in the caliper/master cylinder.


I wouldn't see why just using copper washers would be a problem.. Been used for decades for such appliances- I don't like Dowdy, they always seem like the cheaper produced and supplied alternative.

[nice2day]

Hi Blurredman. I've done some very quick calculations. For any given tightening torque on the hose fitting (when using the spanner to do it up) the pressure exerted on the cone end of the hose is about 10x more than the face of the copper washer. The very small area of the cone creates a very powerful seal whereas the large surface area of the washer "dilutes" any given pressure as the pressure from tightening is spread over a much larger area. The hydraulic pressure of the oil when braking pressure can be up to 1,000 PSI (70 bar). It takes a very good seal to hold that pressure.

The DOWTY seal is a very clever invention. The steel outer ring does not do the actual sealing but acts as a circular "cage" to surround and hold a rubber seal in place which can then act as a sort of O ring. As you would know the more pressure applied to an O ring the more it is pushed into the crevices of its containment and the more it seals. The steel ring of the Dowty seal which looks like a washer is the containment device but the rubber inner does the sealing...These are superseding most other washers on hydraulic installations.

PS...Another reason for the superiority of a Dowty seal is that the fixing bolt or threaded fitting can potentially* be torqued up properly against a near incompressible steel ring. Tightening a steel bolt against a copper washer squashes the copper and never really creates the same tightness which can lead to the slackening off of the bolt or fitting in the longer term. *However if the thread is cut in aluminium the full tightening force is likely not to be fully achieved.

Les

[Puffs]

When reading this I thought '1000psi - you must be joking' but some estimating supports it. Maybe even higher.

Those copper rings seal over just a narrow rim, which doesn't have a very big area either. Width about 1.7mm, ID =10mm --> about 29mm². Anyway, it works & is a common way of doing things, also in cars.

Btw, the Nissin on the YZ (no pic) has an attachment similar to what you would get on the ETZ.

[DAVID THOMPSON]

i polish those copper rings on 3000 grit paper and re use them..
buying new ones where i live will make you go bankrupt in short time
dave

[parrbd]

I fitted a second hand master cylinder from a Suzuki DR650 wreck. I had to make up a new hose but they are supposed to be changed from time to time. Works really well and the quality is excellent.

[DAVID THOMPSON]

newer kaw 650 has a lot of hardware that fits a lot of bikes and a dealer with kymco scooters

also looks like a good parts source

dave

[Puffs]

Ta for your edit Les. I love to learn things & hear of techniques I don't yet know, and I didn't actually know those Dowty bonded seals. That's interesting, so I looked them up. They quote a standard temperature range of only -25 to +100℃, up to +200°C for the PTFE version, and that might actually be a bit of a problem for brake callipers? More info: http://www.potterassoc.com/pdf/bonded_s ... _chart.pdf, https://www.tss.trelleborg.com/en/produ ... onded-seal (Dowty developed them, but apparently they were taken over by Trelleborg).

For DOT4 the dry boiling point is 230°C, and I once had a calliper lock on me because of boiling. Under long braking, going down a mountain in a spirited fashion (think Stelvio or Timmelsjoch), brakes can definitely get quite hot and 100°C is too low a limit, and even 200°C is on the low side. Maybe for that reason I only saw those copper rings in brakes?
Another reason might be the OD, which is relatively bigger than with copper washers (typically 16mm OD for a 10mm ID).

David, I'm not sure I could buy 3000 grid here, but I'd guess a bit courser would do too.

[Guesi]

On my Triumph repair manual it is written that a copper gasket can be re-used by heating it up until it gets red
Then let it cool down.

Maybe this is a better way for your copper rings...

[dave47]

My current etz has a copper washer fitted by the previous owner but it should not really be there. It does not leak but I think he might have glued the threads as well, making it a permanent fixture. I cannot unfasten it without risking breaking the alloy. He also forced a Yamaha mirror into the MZ boss and glued that in as well. Also on the clutch side so the lever pin cannot be removed.
Anyway Blurredman is right. The hose should be screwed fully home without a washer leaving a small gap, same as at the caliper end. There is no washer listed in the parts book
Its a bit of a long shot but are you sure the hose fitting is not too short - I assume its a new aftermarket item. The insert should be 13mm long.
re: doughty washers. At a factory where I worked a few years ago, the setter used one to fix a persistent oil leak where a hydraulic hose entered a machine. I do not know if this was good practice or a desperate bodge, but it worked.

[Kruh]

On my Triumph repair manual it is written that a copper gasket can be re-used by heating it up until it gets red
Then let it cool down.

Maybe this is a better way for your copper rings...

Aka annealing.
Did the same with my oild drain washer. I bought a set of copper washer, installed it and it was leaking slightly after a ride. Replaced it two time, with the same result. Even though they were brand new washers...
But after annealing the washer, no issues.

[Puffs]

Thanks, a good reminder from you both!

[nice2day]

In reply to Dave 47

Its a bit of a long shot but are you sure the hose fitting is not too short

Hi Dave the fitting on the hose is standard. As discussed above and shown on the photos I entered here (although difficult to photograph clearly) the threaded hole in effect has no bottom to it...it goes all the way down and through to the cylinder section. With my original round tank version the thread is about 12mm deep and at the bottom is cone shaped with just a very small hole about 2-3mm in diameter. When you screw in the hose fitting, the end of it butts up to this and with further tightening hard it seals. As the new one has no bottom in effect it screws all the way in till the fitting itself meets the master cylinder boss so the only way to seal it is with a washer.

I contacted the seller and with his very tardy reply tells me that "ALL the new ones are the same"....Well maybe they are but I have no way of checking if he is simply selling me a faulty one as I cannot see any other new ones for comparison. I sort of believe him and will probably accept the item and now waiting for some Dowty washers to be sent to me. I was going to use copper ones but having used them before on other jobs, I know Dowty seals are very effective. Maybe as Puffs says, using them at high temperatures might be of some concern but at the master cylinder end, high temperatures are not going to occur unless my bike catches fire.

Hope you have the picture now Dave?

PS: If you buy any Dowty Seals, generally speaking you should buy the "Self Centering" versions. This ensures the washer is fitted concentrically to the the bolt as you tighten it. These type are identified by the fact they have a wider amount of the rubber seal (smaller hole) compared to the original basic type.

Les

[nice2day]

Update: I have fitted the Dowty seal and refitted the cylinder and brake fluid. Not one molecule of leaking fluid has appeared after giving many full pressure squeezes on the lever so I am happy and confident of long term reliability at this connection. As regards the pump itself, well only time will tell but I have to say it's very nicely made and finished with an actuating lever pivot to piston mechanism that appears to have a bellows protection and so better than the original.

If anyone buys this type of new "replica" master cylinder and wants the Dowty seal the size is 1/8 BSP

Les

PS...Not many owners realise that "bleeding" the front brake system is not required as long as the brake caliper piston on the inner (left side...the one with the bleed nipple) has been bled previously and is thus completely full of oil. Unlike cars there is a vertical rise all the way from the right side caliper to the master cylinder, which means any air bubbles rise upwards into the master cylinder automatically if left for a while especially if you leave the bike canted over with handlebars sloping down to the left. After a a few hours just slowly operate the brake lever and the air then finishes its journey out to the atmosphere. By the way do NOT hold in the brake lever overnight this does not work...the brake needs to be at rest to uncover the pump inlet hole.

Les