front brake soft after sitting for weeks

[JS_racer]

hey guys, strange deal here, looking for any thoughts or ideas.
last winter the bike was on the side stand, after several months my front brake was terrible, pulled almost to the bar, super soft. they were great in the fall. My mechanic bled the system and they were great again. now yesterday, the brakes were soft again, the bike sat say a month or so at the shop getting the clutch basket fixed.  ( after trailering home, they felt better, last night had a zip tie on the lever about 1/2 pulled. they feel great now.  (still on the trailer)

thoughts or ideas ?? i do have a mighty vac and other bleeding options. start at the master, then go to the wheel ??
could it be air, or the master needing rebuilding ??

thanks much!!

bike is an 09 with like 87k miles

[3redzxs]

I had to rebuild my rear caliper at 50,000 miles. There was brake fluid showing up on the wheel. I would think that a small leak would give you those symptoms, but it should show fluid somewhere.

[VirginiaJim]

You need to use it more often then it won't be so soft.

Seriously folks, brakes don't get soft just sitting.  I've had my bike sitting for a month or more and it never did this.  But yes, start at the master cylinder and move your way down to the front wheel and see if it gets better.  It could very well be the master cylinder or one of the caliper seals leaking, though.

[JS_racer]

You need to use it more often then it won't be so soft.

Seriously folks, brakes don't get soft just sitting.  I've had my bike sitting for a month or more and it never did this.  But yes, start at the master cylinder and move your way down to the front wheel and see if it gets better.  It could very well be the master cylinder or one of the caliper seals leaking, though.

completely agree it should not be doing this. this was 2 times it did this. spring it was terrible, this time half as bad.
as far as using it more, i have 87k miles in 5 years living in minnesota.     the last month plus was waiting for the part that wares out to come from japan. (clutch basket)

[martin_14]

After trailering home, they felt better, last night had a zip tie on the lever about 1/2 pulled. They feel great now.

What's up with the zip tie? why did you do that? How does that help? Me wants to learn.

[JS_racer]

What's up with the zip tie? why did you do that? How does that help? Me wants to learn.

my track buddy told me to put a zip tie on the lever around the grip, say 1/2 pull. he said to leave it for several hours, i left it overnight.
no clue what the idea or theory is, opens the valve ?? lets an air bubble rise ?? raises good spirits that finish the bleeding process ?? not entirely sure. lol 

[gPink]

Theory is the seals around the piston stick to the piston instead of letting the piston slide in and out of the seals. Pumping lever pressure and tying overnight will let the seals and pistons separate so the pistons will remain in the proper position for the next application of the brakes instead of retracting to far back into the caliper leaving you to have to pump the brake lever the extend the piston back into contact with the caliper. I have had some success with this, other times had to clean/rebuild calipers.

[stevewfl]

Seals dry and the fluid sitting in the caliper gets thick/gross/nasty, thats the 109th reason not to let a bike sit for extended periods.  Eventually that piston moves "in/out" freely no more.

Simple directions all over the 'net plus youtube on how to rebuild the motorcycle calipers with fresh seals. Simple and cheap to do it.

[Rhino]

+1 Rebuild calipers and master with new seals and replace fluid. Not that hard and your brakes will perform like new again.

[JS_racer]

Seals dry and the fluid sitting in the caliper gets thick/gross/nasty, thats the 109th reason not to let a bike sit for extended periods.  Eventually that piston moves "in/out" freely no more.

Simple directions all over the 'net plus youtube on how to rebuild the motorcycle calipers with fresh seals. Simple and cheap to do it.

87k miles in 5 years living in Minnesota,  fluid flushed every year.  Yep must be old nasty fluid sitting for long periods of time, 
Rock on with your fob battery!

[JS_racer]

Theory is the seals around the piston stick to the piston instead of letting the piston slide in and out of the seals. Pumping lever pressure and tying overnight will let the seals and pistons separate so the pistons will remain in the proper position for the next application of the brakes instead of retracting to far back into the caliper leaving you to have to pump the brake lever the extend the piston back into contact with the caliper. I have had some success with this, other times had to clean/rebuild calipers.

+1 Rebuild calipers and master with new seals and replace fluid. Not that hard and your brakes will perform like new again.

thanks much guys, makes sense.

[elp_jc]

fluid flushed every year

That being the case, at least you don't have to worry about rusted brake parts. Now, a soft lever on a well maintained bike like yours (no ABS module internal damage or leaks), usually means one of 2 things: air in the system, or a leak. Without any external leaks (you didn't report any), the only other option is the master cylinder (internal one) indeed. I'd only do exactly what you proposed, and in that order: bleed the system first, including the master cylinder (you have a valve for that too on this bike). And fill both reservoirs to the max line when level (bike must be on centerstand, and bars moved until reservoir is level). If that doesn't solve the problem, then it's going to be the master cylinder (leaking brake pressure into the reservoir). No need to mess with the calipers on a such well maintained bike IMO, unless they give you trouble. Good luck.

[martin_14]

great thread, I'm learning