Topic: Cb550 front disc brake

[Anthub]

Sent from my iPhone using Tapatalk

[Anthub]

Okay... so today I’ve swapped the forks round and the caliper is now at the front... I’ve bled the system like crazy and when checking the bleed hose by shining a light through it I could see what can best be described as a wisp of bubbles, so fine they kind of looked like smoke coming from the bleed nipple, pretty much on every squeeze.
On checking the brakes, pretty much nothing has changed!! I can still nearly get the lever to the grip and can still rock the bike forwards with full front brake.
Even though the caliper piston is very clean, with no evidence of leaking fluid, could air get past the seal? Is it worth rebuilding the caliper?


Sent from my iPhone using Tapatalk

[Stev-o]

Doesn't surprise me that there is no improvement as you didnt technically change anything.
How old is the caliper seal?  Still thinking the issue is the MC...

[Anthub]

Well I did put the caliper back in its correct position which should have helped with bleeding.... apparently.
Don’t know about the caliper seal as I’ve only had the bike a couple of months.
On a positive note, I’m not getting bubbles in the master cylinder now and the lever has firmed up a bit (not much but definitely a bit better)


Sent from my iPhone using Tapatalk

[TwoTired]

I've noticed that the bubbles stay large until the fluid is under pressure.  Then they get tiny.  Tiny bubbles rise sooo slowly.  Far slower than large bubbles.
So, when I bleed , I make every effort to hardly apply any pressure to the system until the large bubbles stop popping out of the master bleed hole.
I'll use quarter strokes on the lever, wait 15 secs. And repeat untill the big bubbles stop. Then I'll apply just a little pressure and wait, then try quarter strokes again, watching for bubbles.  If I ever see tiny bubbles, I know that it wiil take overnight for these to rise to the top.  Next morning, quarter strokes usually get the rest of the bubbles, and I get a hard lever.  For overnight, I make sure the fluid system is arranged so buble can't get trapped lower than the master cylinder.

I have bled the whole system without ever cracking the caliper bleeder, and gotten a rock hard lever.  But, that does take some patience.

Cheers,

[scottly]

Remove the adjuster screw and spring.
With your fingers wrapped around the rotor, press the caliper firmly with your thumbs.
This will push the piston into the caliper, forcing any air up and into the MC through the tiny bleed hole.

[Anthub]

Cheers guys ... appreciated


Sent from my iPhone using Tapatalk

[strynboen]

you can take the marster off the bike  and hold it over somthing to take the fluid...then hold a finger for the end..as a return valve..press the handel and let the air sqveeze thrugh ,,as you pump...after 4-5 pump the marster is total airfree..and then Mount it on the bike..and carefull start to pump..

have you thekked that the pump piston goes the vhole vay back in the marster..have see sone vho hang..så it missed the last hole konnekted to the resuair..that maked it not get direkt kontakt to the beholder..so it not filled the bore..and it pumped just air

[Anthub]

Thanks.. I’ll bear that in mind....
Scottly, I tried your suggestion this morning re compressing the pad against the rotor and although I didn’t get any bubbles in the reservoir, I did notice that when pushing the pad back onto the rotor using the lever, there was no movement of the pad until I got past the half way point with the lever... That took me back to something I alluded to way back in this discussion that the brake lever may not be correct for the bike and therefore not producing enough levering force. Looking at images of stock levers, there does appear to be a slightly different profile!! For the sake of £5, I’ve ordered a new lever... Here’s a photo of the one from my bike and below that, a one taken from an image on eBay


Sent from my iPhone using Tapatalk

[Anthub]

Sent from my iPhone using Tapatalk

[Anthub]

Sent from my iPhone using Tapatalk

[strynboen]

do you have a fev milimeter slup/free.. in the handel..so you are shure the piston goes komplet back..and opens for the fluid...up in the tank..so fluid goes dovn and air goes up.

..think the free back travel is more importment then the forvard push..it normaly not so kritical..so dont think a handel can do so large different..but try it aut..

[Anthub]

Sorted!!!!
I have carried out pretty much all of the advice given and have finally got rid of all the bubbles.
I was however still able to pull the lever to the grip but I fitted the lever this evening that I ordered through eBay and the difference to the pressure was much greater due to its different profile... The front wheel will now not  move when the lever is fully applied.. Thanks to all of you for taking the time to give me all the excellent advice


Sent from my iPhone using Tapatalk

[CBGhia]

Are you still able to pull the brake lever back the the grip, now that the new one is installed?

[Anthub]

Nope!! About 20mm away


Sent from my iPhone using Tapatalk

[Stev-o]

Good to hear...

[strynboen]

then on to the battery Loose voltage,, and rattel cam thain..and leaking kaburettors..and all the normal issues on cb 550...

[Anthub]

... I fixed my rattly cam chain last week... Sounds like a dream now


Sent from my iPhone using Tapatalk

[strynboen]

one less to go for...one day it all Works fine..and you bay an othet vrack to start all over...Again..

[Anthub]

... thanks again for your advice ... even going to the effort of doing a video


Sent from my iPhone using Tapatalk