Brake pedal free play TE 310

[2wheeler]

Hi all, Looking for advice and next steps on this. Pedal has approx 3/4" or 19 mm free play before the brake engages. The manual calls for 5 mm. Wheel is off the ground, measuring just in front of the foot pad.

Background:
All was normal until riding after the swingarm, linkage, and shock had been removed and replaced. I had loosened the master cylinder for more clearance to get the shock out. The master cylinder lost a small amount of fluid near the cap. The rod attached to the pedal separated from the master cylinder. And yes, the brake pedal got pressed with the wheel off. Upon reassembly, I pushed the piston back in pushing against the brake pad. Pushed the rod back into the master cylinder.

Action taken:
Pads have plenty of material left on them. I have reverse bled 5 - 6 ounces of dot 4 using a syringe with hose zip tied to the syringe and the bleeder. (tapped air bubbles out of hose and syringe) Did not allow brake fluid to go below site glass while syphoning. Filled the reservoir to the notch above the site glass. (I do not see the site window marks mentioned in the manual)

Option?
I hesitate to adjust the free play as described in the manual. Will that not misalign any fluid channel that may be in the master cylinder?

 

[Trenchcoat85]

nothing you did should have affected pedal travel- so maybe do not adjust anything until you solve the mystery.

first thing i'd do is unbolt the M/C and suspend it high (cap up!) so any air trapped by the "swingarm" bend in the brakeline can migrate up. maybe rotate the caliper on to different sides occasionally. aggressively pushing the slave piston in can get air moving up too; push the master piston back up if you wanna try a couple times, but it's gotta be at the lowest position for air to pass up into the reservoir iirc.

i do not recall a sight glass on the rear. i'm a bit too sick to take a look though. clean the cap vents and bladder.

if you're using the same pads & rotor, not much should've changed. make sure the caliper itself is free to move to-and-fro in its mount.

after all the air is out (2 days??), rebolt it, refill and pump the brake pedal 10x. fingers crossed.

pedal initial position is adjusted by the eccentric wheel and pedal travel is by the heim fitting nuts on the master piston rod; sounds like you figured that out.

 

[2wheeler]

Pumped pedal 20 times no change. Pushed caliper in and it moves. Suspended master cylinder. Previously had gently wiped the bladder and gotten any crud off of the ‘breather’ slots on the cap. I don’t believe there is a pass through between the two ‘breather’ slots?

 

[Johnrg]

Only thing I can think is maybe caliper isn't fully clamping with both pads and caliper needs to pull in more. Pumping the brake firmly should take care of that unless the sliding pin is sticky. As long as the round pedal stop hasn't been changed, not sure where you gained the extra play. On the site glass mine is fully submerged/lower than the fluid level. Is your rear wheel spacer in on the right side? Can't think of what else might cause your issues. A few pics of mine to compare.

 

[2wheeler]

Trenchcoat hope you are feeling better. Have the same pads and rotor. No change after suspending the master cylinder. No visible fluid leaks.

Helpful pics John, thanks. Got both spacers on.

I could push the caliper in by hand. Still I removed it, cleaned the pins, they were a little dry. Greased them and reassembled. Bladder is good, no damage. There is a pass through between the vent holes. With the cap off of the master cylinder I had the fluid at the groove just above the sight glass. Syphoned some out to about 1/8 below the top of the sight glass and reinstalled the cap. With the cap on the fluid is either at the top of the glass or above it. Pumped many times, no change in pedal travel.

It is quite noticeable that my wheel and push rod adjustment are both set differently. Although I have never changed either one.

Pics of the pedal travel, adjusters (pedal depressed), and caliper

 

[Johnrg]

About same play as have I think. Maybe 1/8 in. diff. Maybe something was sticking or in the pads before you dissasembled and now seated better? Adjust the adjuster and stop and ride it and check again after. When mine was new it had very little play and pedal tip too high so barely the threads on that adjuster to allow it to be tightened/lowered. Adjust the stop so it rests where you like it.

my free play:

 

[2wheeler]

Thanks John. Ran the push rod adjuster up some. Removed a little bit more fluid so that the level was at the top of the site glass when the cap was in place. It would appear the grove inside the master cylinder is not necessarily the fill point. But, not sure. Tried searching the web but did not find anything definitive. I did watch a vid of a Brembo rear rebuild that looked very similar to this one. It was on an older ktm. Looked like a basic bore and a piston with no special channeling, etc. Came across a supplier with decent pricing https://www.oppracing.com/

Pedal feels much better. Will take her out tomorrow

 

[2wheeler]

Did 45 miles with a couple of 690s and a 701 today. Plenty of rocky, rutted downhill descents. Brake works great. Thanks guys!

 

[R_Little]

OT:

The Master cylinder push rod adjustments on all my bikes seize. I try to loosen and the snap.

I guess you have to put anti-seize on them or something.