The front brake is killing me (mentally)

Stillreel · Nov 19, 2012

I was experiencing the same issues and did the same re-sleeve as described above.

I'm thinking that the position of the piston relative to the feed holes in the MC is critical.

Both MADASS and I have wondered if the holes in the MC are consistently located to all cylinders and may have to be matched to a specific piston. For example, If they are too far aft, the piston may be ineffective. When the piston is not correctly located to begin its pressure stroke, the lever force simply feeds fluid back into the MC. And, if the piston does not retract enough to replenish brake fluid, there won't be enough fluid to pressurize the system down to the calipers. (Correct me if I'm wrong here).

My fix was the shimming technique. But beware, shim too much and you will leave a load on the calipers, leading to overheating and a seize up. Carry a 1/4" wrench with you for awhile to relieve unwanted pressure if necessary.

BC

Matt Spencer · Nov 19, 2012

A dry system can have residual air on the walls . so typically TWO days and it congeals in a bubble somewhere . near inevitable .

BUT .

a plastic tube on the nipple (ALWAYS ) into a jar ,

and the nipple JUST 1/4 turn out . and lifes a lot more straightforward .

IF YOU DONT PUMP IT FAST .

quite steady stokes . tecnically close nipple when leavers IN at bar .

really your FLUSHING the system. Which isnt a bad idea. Fuids cheapish . use the expensive one .

Aim to push 1/4 litre tru & inspect drained pluid after sitting. any residue / fillings / contaminates .

ALL seals should be Pre Lubed on assembly. doing it dry aint on .

Nortiboy · Nov 21, 2012

Have you got it sorted yet ?

Most posts are leaning towards the holes in the botton of the reservoir not in sync with the piston. A quick check is leave the lid off the master and push the brake pad/s back with a flat screwdriver. You should get a significant squirt of brake fluid coming from the master cylinder so cover anything of value.

If you do not get a squirt, we are moving in on your problem.

A trick I use for bleeding stubborn master cylinders is to pump up, hold down and crack the hose connection at the master and repeat.

A sleeved master is as good as any master out there, so lets get it sorted.

Cheers

calbigbird · Nov 21, 2012

Hey everyone, thanks for all the input. I tried doing the old zip tie the brake handle and ignore it for a couple days trick. When I first took off the zip tie, I had acceptable brake lever travel and a really firm brake feel. I left te zip tie off for a few hours and rechecked the lever. I found slightly more travel in the lever and the feel wasn't quite as solid, but it seemed to be acceptable. I'm going to leave the lever loose over night and see what I have in the morning. There is, however a definate improvement from what it was. If it stays like it is now, I'll be a happy biker.

Thanks to all,
Craig

J.A.W. · Nov 21, 2012

Did you do ALL the suggested air bubble elimination measures? Don't come back crying in frustration if 'n' ya didn`t...

calbigbird · Nov 21, 2012

J.A.W. said:
Did you do ALL the suggested air bubble elimination measures? Don't come back crying in frustration if 'n' ya didn`t...

About the only thing I haven't done is crack the master loose at the hose joint while under pressure. I had a friend suggest air might be trapped in the horizontal hard pipe between the tripple trees. With that in mind, I put the bike on the side stand last night so there would be a bit of an angle uphill just in case. Right now, I'm happy with the way the brake feels. I will take it out for a short spin tomorrow morning, I think that will be a better test of how things are.

If it returns to its errant ways, I promise I won't come back crying in frustration. I may snivel and whine a bit, but I won't cry.

Hope everyone has a great holiday tomorrow.

J.A.W. · Nov 22, 2012

OK, but I have to let you know, I `ve been there, firing tools across the floor, effing & ceein` , even went for a ride - to have `em binding on, `til I tried the one thing you aint...yet tried, & it worked. All the best, man..

Snorton74 · Nov 22, 2012

Save your pocket change for a year, and pick up a Brembo setup and never deal with this problem again.

Nortiboy · Nov 22, 2012

calbigbird said:
I found slightly more travel in the lever and the feel wasn't quite as solid

This is normal. Smaller piston produces less flow and more pressure. If you have a rubber brake hose it can feel quite spongy.

This all adds up to more "feel" when braking.

Take care as the front wheel can be locked up much easier

Cheers

calbigbird · Mar 8, 2013

FINALLY FIGURED IT OUT!!! It was the brake lever. I have a 75 MK III. When I purchased the sleeved MC, I also purchased the correct MK III brake lever. Apparently the sleeved MC wanted the older style "straight" lever. The guy who sleeved my MC tried three different MK III levers and found the same problem with all of them. When we tried an older style lever it corrected the problem. Got a lever made for a 74 and it works perfectly now. For all who have a MK III and have a sleeved front MC. If you think you have too much travel in the lever and can squeeze the brake to or near the grip, try a lever from a 74 or older. It made a major difference in mine.

madass140 · Mar 8, 2013

thats why I now supply 3 different thickness shims which fit over the mastercylinder piston (lever end) with my resleeve kit.
it gives you some adjustment .

kommando · Mar 9, 2013

I have fitted Madass's resleeve kit and found it an easy mod to apply, the sleeve slides in easily and is retained with Loctite, no need to bore the MC out, and as you drill new holes nothing to align. I have added a small 4mm grub screw as secuirity for my own piece of mind but it not needed, the grub screw enters at the handlebar groove on the back of the master cyliner and continues until it screws into the sleeve on the OD away from where the seals run so mechanically stopping it from moving out and rotating. This is also loctited but the handlebar will stop it from unscrewing. The kit comes with 3 shims and also the required drills to remake the holes from the fluid chamber to the bore using the original holes as pilots.

cyclegeezer · Mar 9, 2013

kommando said:
The kit comes with 3 shims and also the required drills to remake the holes from the fluid chamber to the bore using the original holes as pilots.

This kit sounds good, I only have one question. How do you deburr the holes you drill through the sleeve into the bore of the master cylinder?

Bernhard · Mar 9, 2013

This kit sounds good, I only have one question. How do you deburr the holes you drill through the sleeve into the bore of the master cylinder?[/quote]

There are many types of de -burring tools on the market; from a half round Swiss file to ;

http://www.ebay.co.uk/itm/TREND-SNAP-CS ... 5ad946ffaf

http://www.ebay.co.uk/itm/Monument-3020 ... 3f1e34c1ed

or, you could just use a largrt twist drill point in the hole and turn it by hand.

kommando · Mar 9, 2013

I deburred using a piece of wet & dry on a wooden rod 8mm od and it just took a few secs.

Danno · Jun 17, 2015

calbigbird said:
FINALLY FIGURED IT OUT!!! It was the brake lever. I have a 75 MK III. When I purchased the sleeved MC, I also purchased the correct MK III brake lever. Apparently the sleeved MC wanted the older style "straight" lever. The guy who sleeved my MC tried three different MK III levers and found the same problem with all of them. When we tried an older style lever it corrected the problem. Got a lever made for a 74 and it works perfectly now. For all who have a MK III and have a sleeved front MC. If you think you have too much travel in the lever and can squeeze the brake to or near the grip, try a lever from a 74 or older. It made a major difference in mine.

The Madass kit comes with three small shimming pucks to apply to the outer end of the piston and reduce the distance between the lever boss and the piston. I had previously made a shim for this junction that lengthens the boss on the lever.

Just loctited the sleeve into the M/C. Hoping to get drilled tomorrow night, but leaving for Fla. Friday after work. Will report back when all is assembled and bled.

manx850 · Jun 17, 2015

Clubman Racing sell an Andover Norton Grimeca MC for the MK3....a world of difference, bolts right on...................The brake actually works...my original was resleeved with a braided linne etc. still a POS...............

The front brake is killing me (mentally)

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