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Rubbing front brakes. MC return port clogged?

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blacklines View Drop Down
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    Posted: 16 Apr 2018 at 12:57
I've had this ongoing niggle with my front brake sticking for some time and it seems to be getting worse. Rather than ease up with use it seems to stick more the warmer it gets. I checked the rotors this morning after a mile of 30/40 zone, only braking twice and couldn't hold them without burning myself. First track day on Thursday and now I'm a bit concerned the front will lock up on Park straight or something.

I've tried:
  1. Cleaning the calipers on a number of occasions (removed but not split).
  2. Re-aligning the calipers on forks.
  3. Re-aligning wheel in forks.

I'm wondering if it might be the MC return port as the pistons seem free but when I push one in, another tends to pop out indicating some resistance.

Does this sound a likely cause and if so, has anyone fixed this on the Brembo MC?

Thanks



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Post Options Post Options   Thanks (1) Thanks(1)   Quote redratbike Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 13:08
have you checked the free play in the lever???


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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 13:32
Thanks for the reply Redrat. Do you mean how much I can move it before I feel the piston moving or is there a more scientific method?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 13:41
I just checked and it looks like there is no freeplay in the movement of the piston but there is about 4-5mm before I can hear the click of an interlock or something, maybe the brake light switch.

This is my lever. I'm not sure if it's a cheap aftermarket or original.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 13:46
You should have about 10mm of free play at the lever tip before you feel the lever plunger hit the piston. If you don't the return hole in the M/C with remain partially closed off. Overfilling the fluid res will cause a problem too.
That will only likely be the problem if the wheel runs free when cold. If it doesn't then friction from the rubbing will make the disc heat up and expand locking your brake on.
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 13:56
I'll have to pop a caliper off tonight so I can how much lever action is needed to get the caliper pistons to move. When riding there is about 4mm lever travel before I can feel the pads 'touch the rotors' so I'd guess the free play can't be any more than that.

Is there a way to increase free play in the lever?

Overfilled reservoir sounds like it could be a quick win. Now you say it I think I've started noticing the problem gradually ever since I replaced the brake fluid. I'll try that tonight too and see if it has an effect on freeplay. Can see how maybe having more pressure (fluid head?) above the return port could restrict it venting up properly.

Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 14:10
Originally posted by blacklines blacklines wrote:

I'll have to pop a caliper off tonight so I can how much lever action is needed to get the caliper pistons to move. When riding there is about 4mm lever travel before I can feel the pads 'touch the rotors' so I'd guess the free play can't be any more than that.

Is there a way to increase free play in the lever?

Overfilled reservoir sounds like it could be a quick win. Now you say it I think I've started noticing the problem gradually ever since I replaced the brake fluid. I'll try that tonight too and see if it has an effect on freeplay. Can see how maybe having more pressure (fluid head?) above the return port could restrict it venting up properly.

Thanks!
 
It's the M/C piston you need the free play for not the caliper.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Mr Miller Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 15:01

Red arrow is where plunger adjusts ..
yellow arrow will ONLY adjust gap to bar
Spoonz is 100% on .. see  many bikes with too much brake fluid
Hope it`s an easy one the plungers can be a pita sometimes ..
lets ken how yer day goes ...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 15:36
Ah thanks Mr. Miller! Is the pin the red arrow is pointing at eccentric or something? I'll have to look tonight.

I'll start with reducing the brake fluid in the reservoir (about at max line I think) and then see what I can do about adding some free play between the lever plunger and the MC piston.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Mr Miller Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:12
If memory serves it is threaded through the pivot pin (gold head)
and has a very neat slot for adjusting BUT watch out for it being
well tight .. sometimes easier to take the lever off and give it a good
clean.. the pivot pin has a nut underneath (iir)
Hopefully yours will be free and a doddle to do Thumbs Up
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Post Options Post Options   Thanks (1) Thanks(1)   Quote legend88 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:19
Originally posted by Mr Miller Mr Miller wrote:

If memory serves it is threaded through the pivot pin (gold head)
and has a very neat slot for adjusting BUT watch out for it being
well tight .. sometimes easier to take the lever off and give it a good
clean.. the pivot pin has a nut underneath (iir)
Hopefully yours will be free and a doddle to do Thumbs Up


I think it's only the clutch lever that has the adjustable pin as standard although that may vary by model year. If yours is not adjustable then you really shouldn't need it but may be able to retrofit a clutch side pin onto the brake side. Where it is adjustable, the pin is locked in position by a very small grub screw which many people miss which is why they end up mullering the adjusting screw slot.


It's possible you have some corrosion or other grunge in there that is preventing the piston from moving freely. Myabe it's time for a master cylinder rebuild.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:33
It's not unknown for some aftermarket levers to have a different pin length if it came with it's own pin. If you have the original lever/pin I would make a comparison. I remember someone on here having a similar issue at some point and had to shorten the pin a few mm.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:35
Spot on Clap

I've never seen an adjustable brake plunger either,just on the clutch side.  What I HAVE seen are after market levers with the wrong geometry Shocked

This has the exact effect you're experiencing, and yes,those are aftermarket

Rather than try shortening the plunger I relieved the lever itself at the front edge where it stops against the body thus allowing it to open forwards more.   If you get my meaning Ouch

Lets see if this works


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tifa Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:44
I just ground my plunger down a little.
The missus didn't like it...but...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:51
That's a better idea Ian, never thought of that.
 
Tifa, as long as it was her you ground it down with then at least she felt the benefit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 16:59
Trouble with shortening the pin ( ooh err ) is you'll be left with a floppy lever LOL   should you need to change levers again for any reason Wink

Far better addressing the problem directly
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 17:22
Plenty for me to get on with tonight, thanks!
  1. Drain some fluid from the reservoir (can go a little above min level I reckon as the pads aren't too far off needing replacing).
  2. See if the plunger is threaded into the pivot pin. If so, adjust this for more free play (checking for grub screw first).
  3. If no adjustment, try filing the top shoulder of the lever down to allow it to retract further.

Think I'd rather go over the bars than grind off the end of my plunger ha

Thanks for confirming the levers are aftermarkets Ian. They came on the bike and I don't know where the originals are. They look pretty but I'd prefer to have plain levers and cool rotors than nicely machined levers and binding brakes.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 17:38
!/4 hr with a decent file /dremmel/angle grinder if you're careful and you can have the best of all worlds

I expect when you take the lever off you'll find that the pivot pin runs direct in the lever without the brass bush the OE levers have.  This isn't a problem,just make sure to keep it greased and it should last as long as you want.

If you do decide to trim the lever try and visualize the rotation round the pivot pin and remove matl accordingly,stopping frequently and offering it up to check progress.

I set mine to have minimal but definite clearance before the plunger contacts the piston

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Post Options Post Options   Thanks (0) Thanks(0)   Quote legend88 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 17:39
Originally posted by IanG IanG wrote:

Rather than try shortening the plunger I relieved the lever itself at the front edge where it stops against the body thus allowing it to open forwards more.   If you get my meaning Ouch
if this works


That's a good plan Ian. Our Chinese friends probably don't take much care in getting the geometry exactly right. Close enough may be good enough in some cases but definitely not in this sort of situation.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote budd Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 18:55
another thing you may try if the above fails is to clean the fasteners and area where the disc attaches to the central rotor, the discs are partially floating and road gunk/brake debris etc can build up and cause the fasteners (big rivet things not sure the correct term) to stick and stop the disc floating how it should. To clean these you need to release the pressure as the rivet things are sprung, you can do this by inserting a small nut and bolt through the centre of the rivet thing and tighten slightly until it releases it's grip on the disc/rotor using brake cleaner and a suitable small bush clean any muck out until it turns freely, then remove the nut and bolt to return the pressure. You need to do this with each one so a front stand makes the job a lot easier and don't go mad with the nut and bolt you only need to apply enough force to release the spring pressure not crush /deform the fastener.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Al_Rsv Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 18:55
I had the same problem with chinese levers. Went through a couple until I bit the bullet & bought a AVG lever.
I thought about grinding the cheap ones down but after locking the front on my Mille & hundreds of pounds to fix I didnt want to risk it.
Side by side the AVG lever was probably a milimeter in difference to the chi nese lever so the tolerence is very small.
No issues since & although pricey you can tell the quality of the AVGs.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote colinmeadows Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 19:15
why dont you just take the lever off and see if your brakes become free ? after that if your brakes are not free crack a brake line to see if pressure is in the line caused by master cylinder ? if there is no pressure and your brakes are still binding your looking at caliper seals

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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 21:54
Originally posted by Al_Rsv Al_Rsv wrote:

I had the same problem with chinese levers. Went through a couple until I bit the bullet & bought a AVG lever.
I thought about grinding the cheap ones down but after locking the front on my Mille & hundreds of pounds to fix I didnt want to risk it.
Side by side the AVG lever was probably a milimeter in difference to the chi nese lever so the tolerence is very small.
No issues since & although pricey you can tell the quality of the AVGs.



Exactly,that pivot point only needs to be very slightly out of posn and it'll never work right. Although many people wouldn't think about checking such things and you hear about locking brakes then.

I've had  three sets of shorty levers ,all no doubt Chinese although all branded differently. One set went on my old SV thou and the brakes on that were so badly designed a slight miss match probably helped.

Both the others found their way onto my Mille and  Tuono. The set on the Mille went on without any adjustment needed but the most recent set that I fitted to the Tuono ( identical master cylinder) needed relieving quite a bit as the plunger was already depressed slightly before the pin could be fitted.

As long as one is aware of the possibility and prepared to fettle to suit they are good levers,if not then I suppose it's worth paying 3 or 4 times the price for branded units guaranteed to work out of the box.

I'm cheap,I like the quality but refuse to pay that sort of price when I could do as good myself LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Al_Rsv Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 22:19
i hear you. Had chinese levers on all my bikes & not an issue before however after having the Mille lock up & chuck me over the front on my first proper ride really played in my head when I got the bike back on the road. I was almost expecting the front to fold everytime I went I put pressure on the brakes. In the end I found the cost of the higher quality lever a small price to pay. 
Mind you if it happened on my old Honda I would have thought nothing of grinding it down & trying again!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 08:17
Originally posted by colinmeadows colinmeadows wrote:

why dont you just take the lever off and see if your brakes become free ? after that if your brakes are not free crack a brake line to see if pressure is in the line caused by master cylinder ? if there is no pressure and your brakes are still binding your looking at caliper seals



I was following Ian's advice and filing down my brake lever when I noticed that the bind is still there even without the brake lever fitted. This makes me think it may not be a free play issue.

I bled the MC through until the fluid level dropped in the reservoir to a bit above minimum. If it helped it wasn't enough to fix the issue. While I leaned the bike on it's stand a mate spun the wheel. He wasn't able to get a full spin out of it while on his CBR we got a good 3-4 rotations.

I came away thinking it has to be the calipers. So I spent the rest of last night cleaning them up as best I could (they were already pretty clean) and also tried spraying some GT85 on the pistons to give them a teflon coating. I pushed the pistons in and out a number of times and all seems ok as far as I can tell. I'm not sure how much force is normal to push them back in but they seem to move smoothly and uniformly.

What did you mean by crack a brake line? Crack open a caliper bleed valve without pulling the lever?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 08:19
Originally posted by budd budd wrote:

another thing you may try if the above fails is to clean the fasteners and area where the disc attaches to the central rotor, the discs are partially floating and road gunk/brake debris etc can build up and cause the fasteners (big rivet things not sure the correct term) to stick and stop the disc floating how it should. To clean these you need to release the pressure as the rivet things are sprung, you can do this by inserting a small nut and bolt through the centre of the rivet thing and tighten slightly until it releases it's grip on the disc/rotor using brake cleaner and a suitable small bush clean any muck out until it turns freely, then remove the nut and bolt to return the pressure. You need to do this with each one so a front stand makes the job a lot easier and don't go mad with the nut and bolt you only need to apply enough force to release the spring pressure not crush /deform the fastener.


I think the disc is floating ok. I can get a very small amount of free play in it. Plus the drag is uniform and there is no pulsing through my lever when braking. The brakes feel great really, just dragging.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 10:00
Spoke to a local shop who, although booked out for the next 10 days, was adamant all I needed to do was pop out the pistons and seals (soaking seals in brake fluid to prevent expansion) and cleaning inside the caliper piston cylinder.

Last ditch attempt I can try tonight, otherwise it won't be ready for Wednesday. I'm giving a mate a lift in the van to Cadwell so I'll still be going but would be gutting having to sit and watch.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 10:32
Corrosion in seal groves can cause tight pistons don't use freeing oil will swell seals silicon grease i use.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 11:03
Would brake fluid also do it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2018 at 12:13
yes to get you going. New seals would make sure but your short on time.
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