Front brake lever "sticking" -- weird lever behavior

[AC_Schnitzel]

Here are the details:
- 2009 XB12Scg
- 16k miles
- Less than 2 months of ownership (for me)
- Stock brake lever
- ZTL2 brakes

This started happening recently. Prior to this, the front brake operated normally -- as in, the amount of force required to squeeze the lever was linear (and equivalent) to the amount of stopping power the brake applied.

The Issue
- When slowing down from a speed above 30mph, I squeeze the lever and it sticks to a point and provides maybe 20-30% braking power
- I need to squeeze the lever harder to slow more, and with enough force it goes past the "sticking point" and immediately gives me 60-80% power -- causing my front suspension to compress and jerk the bike forward
- There is no in-between when approaching a stop between the 30% and 60% -- just a sharp application of braking power

What I've tried
- I brought the bike in to a local shop and they inspected the lever, and bled the brake line w/ new fluid
- Haven't tried much else besides that

Potential Solutions?

Based on reading other threads it seems like my solutions could be:
- Glazed/damaged/dirty rotor
- Master cylinder seals are dirty, needs to be rebuilt
- Change fluid and bleed line (which I've already tried)
- Grease lever pivot pin (lever operates fine, not sticky when stationary)

What is the most likely culprit? What should be my next step for diagnosis?

Thanks in advance!

 

[user_deleted]

great description and diagnostics on your part. your comment "i need to squeeze the lever harder" is the clue. you have either 1 or more sticking caliper pistons.....or a corroded/internally warped master cylinder....or both.
if it were my bike i would go with the simplest as follows:
remove caliper and master cylinder
clean caliper as best you can without disassembling.....and blow out brake lines to be sure no debris or corrosion inside same.
the master cylinder MUST be rebuilt. it's aluminum with aluminum inner bore. tricky and tedious to rebuild correctly but give it a try. kit cheap and readily available. here:
bore size-1/2 inch.......stamped on bottom of m/cylinder
factory OEM rebuild kit part #N0220F list is $17 same as many sportsters and big twins

the "stiff lever" and loss of linear feel at the lever as you actuate it is classic tell-tale sign of failing master cylinder and/or sticking caliper piston......80% of the time it's the m/cylinder.

 

[AC_Schnitzel]

great description and diagnostics on your part. your comment "i need to squeeze the lever harder" is the clue. you have either 1 or more sticking caliper pistons.....or a corroded/internally warped master cylinder....or both.
if it were my bike i would go with the simplest as follows:
remove caliper and master cylinder
clean caliper as best you can without disassembling.....and blow out brake lines to be sure no debris or corrosion inside same.
the master cylinder MUST be rebuilt. it's aluminum with aluminum inner bore. tricky and tedious to rebuild correctly but give it a try. kit cheap and readily available...14mm bore.

the "stiff lever" and loss of linear feel at the lever as you actuate it is classic tell-tale sign of failing master cylinder and/or sticking caliper piston......80% of the time it's the m/cylinder.

Thanks for your response lunatic. The car sat at a used moto dealership for 4 months outdoors before I bought it -- maybe dust/dirt built up on around the caliper which might cause the sticking? I will look to rebuild the master cylinder.

Some questions:
- between ZTL1 vs ZTL2, are there any nuances that I need be aware of when taking off the caliper? Any differences in the master cylinder?
- How involved should my cleaning of the calipers be? (i've only worked on fixed calipers on cars, never floating and on motorcycles)
- 14mm MC rebuild kit works? Should I look for an SAE version, or is this known to work on our bikes?

 

[AC_Schnitzel]

between ZTL1 vs ZTL2, are there any nuances that I need be aware of when taking off the caliper?

NO

Any differences in the master cylinder?
NO

How involved should my cleaning of the calipers be? (i've only worked on fixed calipers on cars, never floating and on motorcycles)
the calipers do not "float". the rotors slightly do. clean as you would an automotive caliper. clean outside extremely well and around the piston dust seals. squeeze each piston fully into its bore to expel all fluid and break any rust/corrosion loose inside the bore. leave it go at that.

14mm MC rebuild kit works? Should I look for an SAE version,

NO and YES
here ya go. use OEM kit. or order from any dealer. i provided you with the part #.

https://www.ebay.com/p/99-10-Genuin...it-N0220-f/1852584994?iid=392096276489&chn=ps

Great -- ordered the MC kit and banjo bolt washers from SPHD. Will do the rebuild/cleaning the caliper at the same time... Will rebuild caliper if the problem persists after trying everything aforementioned.

For caliper removal, the video I've seen online has the front wheel being removed... Is this a necessary step?

EDIT: it looks like you're saying to clean the caliper without disassembling... Does this mean with it still semi-mounted to the wheel/rotor?

 

[user_deleted]

For caliper removal, the video I've seen online has the front wheel being removed... Is this a necessary step?

i always do.....yes. just much easier and prevents rotor/wheel/fork lowers from being scratched and gouged.

it looks like you're saying to clean the caliper without disassembling... Does this mean with it still semi-mounted to the wheel/rotor?

you're going to want to blow out the brake line after both m/cylinder and caliper removed. remove banjo bolt/line from caliper then do your caliper cleaning. simplest and best way to do it properly PLUS you preclude the chance of putting undue stress on the hose fitting and tearing it. also makes it much easier to compress the pistons into the bottom of their bores. do NOT disassemble caliper. dis-assembling the caliper and rebuilding IMO unnecessary and beyond your abilities. just do what i suggested to do. bleed entire system when done. i use DOT-4.

 

[ocgreenmachine]

question, have you ever tried to put some grease on the pivot pin of your lever? I get slight sticking where it would catch slightly from time to time similar to what you are describing and cleaning and greasing that pin fixed the problem.

 

[AC_Schnitzel]

question, have you ever tried to put some grease on the pivot pin of your lever? I get slight sticking where it would catch slightly from time to time similar to what you are describing and cleaning and greasing that pin fixed the problem.

I haven't tried that yet, although it looks and feels like the lever operates normally when stationary.

UPDATE: I found that the previous owner might have improperly torqued the front rotor and have noticed that one (or more) of the bolts aren't fully tightened. There is play between the rim and the rotor.

Obviously I will fix this ASAP by checking and applying the proper torque spec to all bolts, but can this be a cause to the braking issue?

 

[njloco]

That can't be good ^^^^^^^^^^^^^^ !

 

[oh9bolt]

The front rotor is a floating rotor the bolts shouldn't be tightened all the way to the wheel.

 

[AC_Schnitzel]

Not my video, but this is the same play I'm experiencing... Is this normal?



EDIT: found this link on BWB -- http://www.freepatentsonline.com/6561298.html

I guess it's supposed to operate that way...

Going back to my original plan -- rebuild the MC and clean the caliper

 

[user_deleted]

but this is the same play I'm experiencing... Is this normal?

yep.
do what jesse said. remove each rotor bolt ONE AT A TIME.....clean threads....make certain rotor positioning spacer correctly installed(rounded edges towards wheel center)....1 drop of blue loctite on bolt thread....reinstall. torque to front 25-27ft. lbs

it's all in here. you need this......................
http://buellmods.com/content/downloads/manuals/2009_xb_service_manual.pdf

 

[Cooter]

I don't want to confuse this well taken care of thread. But...

The ZTL M/C is 14mm, and one for the later ZTL-2 is 19mm. (IIRC, but they are definitely different)

I've had sticking problems with the lever similar to what you describe and a touch of grease on the tip of the M/C piston will allow the shoe on the lever that contacts it to slip across its face and make it surprisingly smoother.

 

[AC_Schnitzel]

I don't want to confuse this well taken care of thread. But...

The ZTL M/C is 14mm, and one for the later ZTL-2 is 19mm. (IIRC, but they are definitely different)

I've had sticking problems with the lever similar to what you describe and a touch of grease on the tip of the M/C piston will allow the shoe on the lever that contacts it to slip across its face and make it surprisingly smoother.

St. Paul HD says that my parts are on backorder -- so it will take a while longer to get the rebuild kit.

In the meantime, I put some dielectric silicone grease on the tip of the MC piston. It had some build up/oxidation on the surface.

I also put it on the pivot pin as well...

Haven't test rode it but it feels much much better. Less "squishy" and I'm pretty confident that this will improve braking.

Will report back here. If it works -- thanks for the idea! Of course I'll still rebuild the MC, after seeing the condition of the piston/plunger.

 

[AC_Schnitzel]

St. Paul HD says that my parts are on backorder -- so it will take a while longer to get the rebuild kit.

In the meantime, I put some dielectric silicone grease on the tip of the MC piston. It had some build up/oxidation on the surface.

I also put it on the pivot pin as well...

Haven't test rode it but it feels much much better. Less "squishy" and I'm pretty confident that this will improve braking.

Will report back here. If it works -- thanks for the idea! Of course I'll still rebuild the MC, after seeing the condition of the piston/plunger.

Cooter -- your suggestion seemed to work.

Although it is a temporary fix, braking behavior/power has seemingly returned to normal. A MC rebuild is in my future, but for now I can stop confidently (and safely).

Thanks everyone for your help!