RGM brake mod - bleeding difficulties

Try leaning the bike on it's side stand with the bars turned to the left so that the master cylinder is the highest part of the brake system. With the master cylinder cap removed and the bleed nipple closed squeeze the brake lever and release slowly or try quickly depressing the lever over a short stroke and releasing and you should see air bubbles appearing from the two holes in the bottom of the reservoir. Continue until air ceases to appear and the lever is firm. Works every time for me.

Myself and a friend both had this problem with an RGM resleeve, and another friend had it with the Andover Norton mastercylinder. Between us we wasted days of our lives trying to bleed these brakes, and found the ONLY way to do it is to buy a large hypodermic syringe (available from e bay for a few quid ) and pump the fluid up from the bleed nipple.

I guess this happens because the air bubbles which want to float up are now moving in the same direction as the fluid.

I seem to remember it also helped if the pistons are pushed right back, as there is then less air in the hydraulic space.

I have also had the same problem with the Andover Norton system. Found that the same method as Simon used worked fine but beware that it can splurt fluid out and so cover the tank etc. just in case. I found that the lever never had such a stop/go firm feel as before, perhaps not surprising with the smaller bore, and of course there is more travel, however it gives excellent braking (it is combined with a pre-fittedcheap! Norvil disc/caliper).

The instruction sheet that should have come with our (Andover Norton's) brake kit says you need to use a suction system- as used for cars, available at every garage if you don't have one- to get the air out of the system.

The braided steel brakeline has a smaller bore than a conventional one, and air bubbles tend to be trapped inside it and do not rise up as they do in conventional systems.

Unfortunately there were no instructions with my Andover Norton brake kit, but fitting was easy. I have a suction system which I connected to the bleed nipple but did not succeed in bleeding it properly. However the 'pump the lever' system finished the job and the result was excellent.

Joe - in view of what has been said about Grimcea in another thread, can you say whether or not master cylinders are still being made available, and also replacement seals?

Andrew

After spending days trying to bleed our RGM resleeved cylinders with no sucsess, we phoned RGM to tell them anout the problem. We had to send the cylinders back to RGM for him to alter them, but I dont know what was altered.

So perhaps you should phone RGM for some advice.

It was after the alteration we had to bleed by back filling. And as I said, we tried everything befor we resorted to back filling. Both of us have bled hundreds of brakes successfully in the past.

The whole experience put me off the conversion, and I dont really trust it any more and I dread having to bleed it again.

I must say though that the brake does work well, it can almost lock the wheel with a firm squeeze. There no sponginess at the lever. The brake starts to bit almost as soon as I move the lever.

I will probably move to the Andover Norton master cylinder at some time.

Joe - in view of what has been said about Grimcea in another thread, can you say whether or not master cylinders are still being made available, and also replacement seals?

Richard, all I can say is we still got master cylinders, seal kits, and replacement levers. I guess we will find out about Grimeca shortly, when we re-order master cylinders. As far as I know Grimeca exists. It is not uncommon for Italian companies to be put in the care of a liquidator- I guess MV Augusta got several cabinets full with paperwork about the various liquidations in their commercial career, not to mention Ducati...

I saw the story about Grimeca not being there anymore as the lame excuse of some supplier who lost interest in the Grimeca products.

Hi Andrew, when I fitted the RGM sleeved master cylinder I had great difficulty obtaining a good brake lever pressure. After hours of pumping, the brake eventually firmed up fairly well. Some years later I fitted a new Grimeca calliper and it bled perfectly after a few pumps of the lever and works brilliantly now. So, I guessed the old original "fist" Lockheed calliper was to blame and had been on its last legs and worn out. Back when I had a T140 I finally managed to bleed the brake only after I`d fitted a new rear master cylinder. In extreme cases , I guess that even pipes or hoses within the entire system could allow air to seep in .

Cheers

Chris

I have used the RGM conversion for many years and recently decided to change the seals and piston. It was worn on all sides (flats) but it had not failed me so I figured it was worth rebuilding. Mine is the older glued in sleeve and there were traces of epoxy in the caliper! Too small to cause a problem but still! I mentioned it to Roger at RGM. I also bled the system this time using a syringe via the bleed nipple and it does work but I finished off with the old wives method of clamping the lever to the bar overnight. Brake is better than ever.

The rear brake caliper on some old airhead BMWs were notoriously difficult to bleed. I had one such bike, a 1981 R100RT, and found no problem bleeding it in the conventional manner ie pumping the brake pedal and opening and shutting the bleed nipple. Itworked because Iunboltedthe caliper, removed it from the disc and put a piece of wood between the pads, then raised the caliper above the height of the master cylinder. A similar method could be usedfor the Commando front brake; rather more awkward to do and would be best done with the help of an assistant.

When any master cylinder is first set up the start point for the pistonis most important.It is setby adjusting a screw on the lever for example or the screw and plunger on the RGM conversion. The instructions invariably make this very clear, but if it is difficult to comprehend then it is perhaps missed. If set correctly, when you first move the lever then 1 to 2 mm of piston movement will eject fluid from the hole back into the reservoir before the piston closes that hole and carries on to feed fluid down the hose. If no fluid comes out because the hole is already closed then you will never prime the system and air bubbles will never flow up and out. If fluid keeps coming out for too much piston travel then you are wasting lever movement (and with the RGM small bore piston you need all the lever movement).

Pressurising the calliper with a pumped system or a syringe is the best way. Brake bleeding the old fashioned way is ALWAYS difficult, until you get the knack and follow a system. I can get it to work.1) Pull in the lever STEADILY (only after the small hole is closed) with the bleed nipple open a quarter turn, with a length of clear plastic tube to observe the bubbles. 2) At end of travel lightly close the nipple, now release the lever VERY SLOWLY taking 10-15 seconds. 3) Pump down perhaps a whole reservoir of fluid (top it up) and you will see the outflow become mostly bubble free. 4) Tighten the nipple, pull the lever back with fat rubber bands or a piece of inner tube, go away and leave it like that all night. Air bubbles will slowly migrate up the brake hose and out of that small hole; angle the handlebars to help this. 5) Next day you might have a firm lever, or if not just repeat a few pumps and rubber band again. Sometimes I have taken the calliper off and rotated it (with hose still affixed) while pumping to give air an easy escape.

Problem solved everyone!!!!

I used a 50ml syringe, filled with fluid. Strap a receptacle under the reservoir on the bar. Connect syringe to bleed nipple and squeeze carefully. The overspill is caught in the container. Repeat again. Job done.

I will say there is a lot of travel on the lever but it seems to nip up the wheel very well. Should be able to road test soon so will update you all then.

Andy

Previously andrew_orr wrote:

My master cylinder has been adapted with the reduced cylinder supplied by RGM. A local engineering company did the drilling and tapping. I fitted the new bore myself. All seemed to go together OK. I kept everything scrupulously clean! On reassembling the brake system on the bike it was time to bleed it through. Trouble.

I get a pathetic dribble of fluid from the bleed nipple and the fluid seems very aerated. I'm using a bleed kit with oneway valve to help. Before I strip everything, is there something I'm missing or doing wrong? I can hear the piston going in and out and a few bubbles appear in the reservoir. If I disconnect the brake hose fluid will siphon down from the reservoir to the end of the hose ok.

Any ideas?

Thanks everyone.

Andy

andy,, i like other people have had problems,after wasting hours

trying to bleed the system i sent it back to rgm [i think he altered the piston length ]i then had a brake but not a lot better than before/i then used a master cyl from a hinkley triumph and

only half a dozen pumps on the lever the brake was better than ever

Drill/tap out the caliper and fit a larger bleed nipple, simples!

Just a small point and sorry if its been done, you need to make sure the piston returns fully to bleed it. I have had to grind a bit off the lever to ensure the piston returns fully out. Not just limited to Nortons, one of the common issues when bleeding an awkward brake.

I've done all the standing upside down with the master cylinder balancing on my right leg at 110 degrees, usually comes down to something basic.

Just my tuppence worth

Its great to be back...........

Hi Andy

I gave up trying to bleed the system after fitting the RGM resleeved master cylinder and bought their Grimeca calliper. Including this in the system it bled up after a few pumps of the brake lever and has been brilliant since.My original ("the fist", is it known as?) Lockheed calliper had always given me bleeding problems so I was glad to get rid of the bleeder ! The RGM resleeved m/cyl works fine on my bike.

Cheers

Chris