Brembo front brake, no lever pressure

[Jay GTI]

I was moving my bike around on the weekend and noticed the front brake has completely lost pressure. I can pull the leaver all the way to the bar without any resistance. No obvious signs of fluid leak and a quick check of the reservoir shows it's still full of fluid, which is clear.

I have yet to try a quick bleed to see if air has got in the lines somehow, but if anyone else has any pointers I'd appreciate it.

Interestingly there was no issues on the last ride, all was working as it should.

[Dogboy900]

I am no expert but does it regain pressure if you pump the lever?
If it does I would suggest air in the system.
If it still has no pressure you have a major leak somewhere.

Thats about as much help as I can be sorry.

[Jay GTI]

I am no expert but does it regain pressure if you pump the lever?
If it does I would suggest air in the system.
If it still has no pressure you have a major leak somewhere.

Thats about as much help as I can be sorry.

No, pumping the lever does nothing and there's no leak externally. I'm thinking an internal seal has gone, but usually that is shown up with dark or cloudy fluid in the reservoir.

[imdying]

Does it have braided lines?

Do you see fluid squirting back up into the reservoir during the lever stroke?

[bogan]

Pistons moving at all?

[Jay GTI]

Braided hose, but haven't checked if there's any movement of fluid in the reservoir when pumping, will do tonight.

The caliper pistons don't move at all, that is the odd thing, there is absolutely no pressure in the system at all, yet it was all working perfectly last ride.

[mossy1200]

Small hole at bottom of fluid bowl has blockage so its not pushing fluid with the plunger.

[Jay GTI]

Small hole at bottom of fluid bowl has blockage so its not pushing fluid with the plunger.

Ah that would make a great deal of sense... cool, will empty, clean, fill and bleed, see if that works.

[imdying]

It's a very small hole, find some fuse wire. There are probably two there, so check them both (one is larger; the small one is very small indeed).

[Jay GTI]

Couldn't easily get to the hole, as there's a mesh cover over it, so before I started draining the fluid I gave the pistons a squeeze by pushing hard on the side of the calliper, lots of bubbles in the reservoir and pressure back.

Been reading up about KTM/Brembo front brakes and it's a common problem, a popular workaround is to stick a CRF450 master cylinder on instead of the Brembo one. The calliper squeeze is also recommended as the best method of removing the air bubbles, as normal bleeding generally doesn't work.

[jellywrestler]

Couldn't easily get to the hole, as there's a mesh cover over it, so before I started draining the fluid I gave the pistons a squeeze by pushing hard on the side of the calliper, lots of bubbles in the reservoir and pressure back.

Been reading up about KTM/Brembo front brakes and it's a common problem, a popular workaround is to stick a CRF450 master cylinder on instead of the Brembo one. The calliper squeeze is also recommended as the best method of removing the air bubbles, as normal bleeding generally doesn't work.

the shit that blocked the hole is still in the fluid, repost when it's back so we can have some more entertainment, and tell you it's a good idea to flush the fluid out and put some new stufff in there

[mossy1200]

the shit that blocked the hole is still in the fluid, repost when it's back so we can have some more entertainment, and tell you it's a good idea to flush the fluid out and put some new stufff in there

+1 the squeeze moved the blockage away from the hole. It will want to go back again just when you really want to stop.

[Jay GTI]

Yes yes, I am an idiot but not that much of an idiot, I will be doing a flush and proper bleed as a matter of course on the weekend. I don't trust it as it is, for the reasons you state and I really don't want to barrel into a tight corner and discover it's suddenly returned.

I was just surprised at how much air came out from the calliper squeeze method, as that was definitely contributing to the lack of pressure. As said, it's a known, common issue with the Brembos.

[Shadykiwi]

Its happened to my 2013 350SFX bout 3 times, I also have a mate riding the EXC250 same thing couple times. Usually it happens if the bike has not been used for a couple weeks. Generally I open cylinder give the lever a few pulls and see if any bubbles come up, then loosen the caliper bleeder and release any air down there. This tends to fix the issue but it can take some time for the pressure to build back up. My mate cable tied the lever fully closed over night, same deal next day pressure slowly came back. I'm sure there is a legit reason for this happening and I have fully flushed the oil out before with same thing occurring but I have never had any loss of brakes once pressure is back.

[grantnz]

the shit that blocked the hole is still in the fluid, repost when it's back so we can have some more entertainment, and tell you it's a good idea to flush the fluid out and put some new stuff in there

It happens with new bikes though, with new fluid. ( A mates' Panigale ,Brembo top and bottom) My new MV has Brembos' below and Nissin reservoirs.

[Yorkshire Pudding]

I have just bought a KTM 640 adventure 2004, been in a shed for 7 years, no pressure at the front brake, same as you said, I can see the small hole, so I will clean blow out etc. before I looked in this forum I did try to bleed, vacuum method by pulling the fluid from the master to the bleed nipple, I got clean air free fluid, but still nothing at the lever. I will stick it back together tonight and try to bleed again.