F@$*in Brakes! - Convert

I have now tried every way to bleed this front brake, to no avail. When I squeeze the lever I sometimes see little air bubbles coming up from the hole in the bottom of the reservoir. I have pumped and pumped to see if they will stop, but no good. I just drained the pipe and retried back bleeding with the syringe but still no good, even though it all seemed to work ok. Tried with two different self bleeding pipes, still no good.I earlier bled the linked brakes with absolutely no problems. Is my master cylinder naff? I have replaced seals. I have checked all joints, seriously hacked off now. The Bellagio is sold, so I need the Convert on the road NOW!!It worked ok before I changed the brake pipe!

best thing to do is tie the lever to the bars with something and walk way for a fews hours or pref over night.If youve got the fluid airated you wont get any where fastalso move the caliper round to get the air from behind the pistons and up the pipes

All fresh fluid, but these bubbles still persist when you squeeze the lever to pressure and then release. It is almost there but just won’t lose these bubbles.I am now looking for a new master cylinder!

i would leave it for few hours to settle before the wallet comes out

Think I had this on the Bee-Em, also Brembo brakes, needed new M/C piston and o/h kit to stop the bubbles. Same as you, persistent fine bubbles coming up into the reservoir from the central hole. Suspect may be the outer seal letting air in on release of lever, but just a wild guess.

I had similar problems with my linked system and tried a rebuild kit for the master cylinder which was better but not good enough. A new master cylinder fixed it and the system bled in no time at all and in the time-honoured conventional way. This was after putting in new pads front and back plus new braided stainless steel hoses. It seems that once you disturb it for any reason, it brings out the worst in it, finding any slight fault where it seemed to be ok before. I found that if everything is working spot on and as it should, it will bleed no problem at all.

There you go, if it won’t bleed, must be summink up somewhere. I have had ‘aggro’ with rear M/C’s before, so I wouldn’t be at all surprised. It’s a “PS15” isn’t it?

I reckon it’s got to be the outer seal, even though it is new. I’ve bled it with the syringe so many times, till there was no air coming up, only to find bubbles from the master cylinder when I depress and release the lever.There are two holes visible at the bottom of the reservoir, the bubbles come from the one nearest the lever end.The spurt from the other.

Sorry we’re talking about front aren’t we, how did I get onto rear? PS12 then? Is looking that way isn’t it?

Don’t worry about a few bubbles if the lever is nice and firm. Any tiny bits of air will work there way out of the system.

The lever has too much travel before it firms up. There is pressure there but I have no confidence in it and its next outing is for its mot.Mike, I mentioned that I bled the rear cylinder/ linked brakes earlier and that went according to plan - no problems.

The ONLY thing is air at the nipples , my V1000 comes within mms of the bars always has, you can adjust the grub screw in the lever .

That is the only thing I have not changed GB. Perhaps they’re next, but again, they were fine before!

I remember! So what the blinking flip I was on about the rear for I’ve no idea Going prematurely senile

Try pumping the lever a god few times, it may well firm up as the caliper pistons settle into place

Wot he said, plus pads if they be brand new. Also I’ve found rust on the discs can push the pistons back and make the result very spongy. Pushing them back and pumping up a couple of times usually solves this.


Had this on a s/h spada many years ago, (not yours NW), turned out the seals in the MC were back to front, they have a fine lip which should be placed inward or outwards to prevent air entering, not sure which as it was a long time ago, worth a check. G.

This is the trouble with diagnosing from a distance

The seals etc usually come ready assembled on a new piston nowadays so it is virtully impossible to get it round the wrong way. (Assuming Luigi in the factory was concentrating that day.) There is also a sheet of instructions in 100 different languages telling you how to fit it.

Mine came pre assembled, but as you say they might have been assembled incorrectly.