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...
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...
