Bleeding brakes (CB1100A non-ABS)

[tod.branko_imp]

Ever since I've changed my brake pads I feel like my brake lever is a bit harder than it used to be, and there is a certain buzzing sound, very faint when under pressure, regardless of how hard I press of how fast I was going, it doesn't change, it's always the same, but it's there. I am thinking I should bleed the brakes even though the fluid looks very clear. I've consulted the manual, it seems pretty straight forward, just like on any motorcycle I've ever had a pleasure of bleeding before, I just wanted to ask if anyone has done it and if there is anything specific I should pay attention to.
In the meantime I'll also swap the new pads I put in the rear because (even though I said they produce no sound and actually work) I found that after a while they've become "wooden" the work fine for low speed modulation but at anything over 20km/h, they feel non-existent and I really need to slam on them to get any feedback. I have a new set of EBC pads so they will slide in just right.
I think I'll also try and clean the pistons, something I've never done but always wanted to, if anyone has done it, also, some pointers are appreciated.

I'll make sure I do a photo story for the "how to" section.

'14 CB1100 STD 5 speed

[max]

I'll get the ball rolling by suggesting to take the calipers off the front one at a time with the old fluid inside.
If the handle feels harder it may need grease in the right place?
and the master piston should move light and free when not building against pressure.

Please measure the amount of freeplay and full pull in the handle and compare the measurement after the job is completed to verify the expulsion of any air, it can be a tiny amount that softens the feel of the handle

Once the calipers are off a piece of 6 mm plywood should fit in between the pistons once the pads have been removed, this will stop the pistons "leave home" whilst they are extended to meet the plywood and the ply can then be removed.

this gives a safe way to clean and inspect the pistons, change the pads,push the pistons home to expel the old fluid, re-mount the caliper and repeat on the other side.

Once cleaned open the bleed nipple and drain the old fluid under gravity with the pistons still retracted, it would be a shame to push the old fluid back into the calipers.

once the new fluid is in the system you can close the nipples, build up pressure and set the new pads, at this time there should not be any air in the system but if bubbles emerge from beneath the stainless deflector give them enough time to rise to the top after each pump of the lever.

replace the fluid and just pump the handle paying particular attention not to let the new fluid level empty the reservoir

May sound more difficult than it is but once the order of things is clear there is no difference with a normal system,
If there is some air trapped it will rise to the top by itself slowly.

I hope someone else has more suggestions.

[Tev62]

The buzzing sound can be quite normal and is often the disk holes just catching on the new pad wear grooves, it is nothing to worry about and should decrease as they wear. I'm not saying this is your problem but it is quite common with new pads.

[tod.branko_imp]

The buzzing sound can be quite normal and is often the disk holes just catching on the new pad wear grooves, it is nothing to worry about and should decrease as they wear. I'm not saying this is your problem but it is quite common with new pads.

Yes I guess that makes sense, it's just something I have never noticed in all the years and different motorcycles, but it's perfectly plausible, I'll see if it's still there after the bleeding,

I'll get the ball rolling by suggesting to take the calipers off the front one at a time with the old fluid inside.
If the handle feels harder it may need grease in the right place?
and the master piston should move light and free when not building against pressure.

Please measure the amount of freeplay and full pull in the handle and compare the measurement after the job is completed to verify the expulsion of any air, it can be a tiny amount that softens the feel of the handle

Once the calipers are off a piece of 6 mm plywood should fit in between the pistons once the pads have been removed, this will stop the pistons "leave home" whilst they are extended to meet the plywood and the ply can then be removed.

this gives a safe way to clean and inspect the pistons, change the pads,push the pistons home to expel the old fluid, re-mount the caliper and repeat on the other side.

Once cleaned open the bleed nipple and drain the old fluid under gravity with the pistons still retracted, it would be a shame to push the old fluid back into the calipers.

once the new fluid is in the system you can close the nipples, build up pressure and set the new pads, at this time there should not be any air in the system but if bubbles emerge from beneath the stainless deflector give them enough time to rise to the top after each pump of the lever.

replace the fluid and just pump the handle paying particular attention not to let the new fluid level empty the reservoir

May sound more difficult than it is but once the order of things is clear there is no difference with a normal system,
If there is some air trapped it will rise to the top by itself slowly.

I hope someone else has more suggestions.

And thank you max, MVP answer. I'll do exactly that. May I ask, what do you recommend using to clean the pistons?
As for the lever hardness I don't think I expressed myself correctly, it's not harder to squeeze just there is much less travel, it starts catching very early

'14 CB1100 STD 5 speed

[max]

Cleaning pistons; i use a strong dishwashing / water mix with a brush and cloth to get most of the dust off, then dry and clean with brake cleaner.

You could remove the pistons completely which would be better depending how freely they move / are oxidised after the cleaning.
The pistons have a different diameter to correct uneven pressure on the pads but they should all move evenly when positioned when they adjust to the positioning by pushing them in one at a time
Then have a look at any corrosion between the dust seal and the primary seal, ( take them out ) i started to use a tiny amount of silicon grease to protect the alloy cases from water or brake fluid corrosion and it helps a lot to move / place the pistons back in position.

The new pads need to bed in and will feel a bit softer to start with, that's why i measure their travel before and after the job to see if there is any air left in the system, it increases my confidence level.

And it would be a good idea to check for air in the calipers by cracking the nipples after some days just to make sure.
Also clean the nipples by spritzing some brake cleaner in the opening to prevent rusting by cleaning the remainder of brake fluid out of the opening after bleeding, just make sure no fluid comes in contact with the brake pads.

As for the reduced lever travel, could be pistons are stuck ( dirt in the square o-ring grooves ) and not clearing the pads as before, if that is the case the wheels would possibly drag on the disks, my wheels are completely free and only occasionally make a touching sound, you may have seen my video how the rear pads are supposed to be moving and clear the pads when retracted by the seals.

[pekingduck]

Worn brake pads seat themselves into the minute grooves of the disc, and thus have the greatest contact area. Changing to new pads means they have to bed into those grooves and wear down the peaks, so thus have less contact area, and require more effort for the same amount of stopping.

This also depends on different pad compounds from different manufacturers. All this may be normal, including the noise, as Tev62 stated previously.

While it seldom hurts to bleed the brakes (correctly, that is) it is probably not the cause. However, because you have to push the pistons into the caliper to make space for the thicker pads, the square-section o-rings are now sweeping a different area of the pistons, an area that had been more exposed to dirt/corrosion, as Max says.