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Discussion Starter #1
The (excessive) amount of front brake lever freeplay (travel) before the brake applies has been discussed a bunch so I looked at reducing it.

There's a limit to how much free travel you can remove. The master cylinder piston has to retract enough to open the bleed port in the master cylinder. Naturally BMW has placed a rubber "bellows" with a slit in it over the bleed port so you can't see the piston opening the port. The "bellows" is the round black thing in the bottom of the master cylinder reservoir, you have to remove the cylinder cap to see it.

With the cap removed, pull the brake lever and you'll see fluid move. This happens at the very beginning of your lever travel and what you see is kind of a "bulge" in the fluid. It will squirt fluid if the fluid level is low enough (or you pull the lever fast enough) so be carefull. This is fluid the piston is pushing out the bleed port before the piston closes the port.

Soo, if we adjust the "threaded goody" on the lever we can move the pistons' starting point so it closes the port sooner requiring less lever movement to close the port and start braking.

Lost you yet?

Now we adjust the "threaded goody". The one with plenty of red loctite on its' locking (grub?) screw that you've probably read about...

Fortunately acetone will dissolve the loctite. With the loctite dissolved the locking screw on mine loosened easily.

You adjust the "threaded goody" to make it longer to push the piston in more. Adjust and try. Get the front wheel off the ground. Rotate it by hand and see when the brake starts to apply. You have to still be able to see the "fluid bulge" in the reservoir. That means the piston is still opening the port. This is IMPORTANT.

I went 2 turns. At 2 1/2 turns I saw a decidedly reduced fluid "bulge" so I went back to 2 turns. I applied purple 222 Loctite to the locking screw.

There's less lever travel now before the brake applies.

This is also what you check after you install aftermarket levers and find your clutch is slipping. You have to adjust the "threaded goody" so the port is opening. That open port is what releases the line pressure in the system.

BE CAREFULL. IF THE PISTON ISN'T OPENING THE PORT YOUR BRAKE WON'T FULLY RELEASE AND THAT IS VERY BAD.

Same on the clutch side. If the piston doesn't retract far enough to open the port the clutch will slip.

Have fun...
 

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Now we adjust the "threaded goody". The one with plenty of red loctite on its' locking (grub?) screw that you've probably read about...

Fortunately acetone will dissolve the loctite. With the loctite dissolved the locking screw on mine loosened easily.
Heck, man! Where were you when I was hauling on my grub screw???? OOOPS that almost sounded rude! 0:)

Good tip about using acetone! I'll remember that next time!
 

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Discussion Starter #4
Heck, man! Where were you when I was hauling on my grub screw???? OOOPS that almost sounded rude! 0:)

Good tip about using acetone! I'll remember that next time!
Gotta be carefull, you're girlfriend might feel left out...

Acetone is the usual primer for "real" Loctite if you want best performance and does to an extent dissolve it. I wasn't sure how it would work on what BMW uses but it pretty much instantly turned it to goo and freed up the screw.
 

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Discussion Starter #5
@tomcatt

Very good advice. Cheers.

How many threads showing are on YOUR Brake and Clutch side?
I only did the brake side and ended up with 9 exposed threads but that's probably 9 +/- 1/2 or so depending... The big thing is making sure the port is opened. That's where the problem seems to be when the clutch slips after changing levers.
 

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And of course port would stay closed if rod is pushing it in too much. So, purely theoretically, it would be better to err on the side of LESS threads showing rather than MORE.
 

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Discussion Starter #9
Yes, thanks for the pic. The piston does nothing except push fluid out the bleed port until the port closes. Sooo, to reduce free travel you put the piston close to the port closing point.
 

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BTW: See how there MUST be some room in the MC reservoir for the extra fluid to go there? Guess what happens if overzealous person with best intentions fills that reservoir all the way to the very top? Where does that extra fluid go when lever is squeezed? That is correct - leaks out through the top.
 

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Discussion Starter #14
BTW: See how there MUST be some room in the MC reservoir for the extra fluid to go there?
The caps' gasket has a trapped air space on the top side of the gasket that makes it near impossible to overfill the reservoir and hydraulic lock the system. It's pretty "idiot proof".
 

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Mine were filled to the very VERY brim with the rubber membrane almost floating on top of it. Not surprising it was weeping and eating paint. I have replace waiting for me at the dealer.
 

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OK so.... LOL

At 7 threads showing my brake has quite a bit of "Nothing interesting happens" slop. Once its starts to grab it does so well and with no issue.

What do you chaps think? Should i bump it up to 8?
 

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Discussion Starter #17
If you want minimal free travel you adjust 'til the port isn't open and go back. Problem is it's hidden so you can't see this happening and can only see the "bulge" in the reservoir fluid from fluid coming out the open port at the very beginning of the lever travel. You're the one that's there to see it on your bike.
 

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Gentlemen, help an old sailor out here. I looked at my brake assembly and what I saw was the "goody" piece with what looks like a 2.0 or 2.5 hex bolt in the end. What I saw underneath was a "red" dot. I'm assuming that that is the dreaded loctited bolt. If what I just said makes sense then all I need to do is remove the loctite and turn the adjusting screw accordingly.
 

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Discussion Starter #19
Gentlemen, help an old sailor out here. I looked at my brake assembly and what I saw was the "goody" piece with what looks like a 2.0 or 2.5 hex bolt in the end. What I saw underneath was a "red" dot. I'm assuming that that is the dreaded loctited bolt. If what I just said makes sense then all I need to do is remove the loctite and turn the adjusting screw accordingly.
What's covered in red and "underneath" is the lock screw. You have to loosen it to turn the "adjuster" aka threaded goody. Acetone will dissolve the red thread locker. A Torx T-8 is the correct tool.
 

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What's covered in red and "underneath" is the lock screw. You have to loosen it to turn the "adjuster" aka threaded goody. Acetone will dissolve the red thread locker. A Torx T-8 is the correct tool.

@tomcatt, thanks for the info, I'm not going to open up the reservoir to check for "bulge" I'm going to turn just a bit. I don't ride that fast where I need such an immediate response.
 
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