Front Brake lever intermittently hard and brakes unresponsive

Joined
Dec 8, 2016
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3
Location
mckinney
Hello - I have a 2001 ST1100. Occasionally when I try to break hard (typically the problem occurs at high speed, and never a problem while stopped) my front brake is completely rigid and I am unable to move the brake lever at all.

The rear brake seems to still work during these times, but not as good as when I am not experiencing the problem.

I have had the break fluid replaced but not sure where else to look. Any ideas are appreciated.

Thanks,
douggerber2
 
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Feb 2, 2009
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Dahlonega, GA
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2018 NC750X
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7666
Sounds like the caliper pistons are seized... Had this happen to me after my 98 ST1100 sat for too long. It's not a hard job... just remove the calipers, drain the fluid, place a thin piece of material between the pistons and the opposite side of the caliper... like maybe a spent brake pad or similar. Inject compressed air into the fluid inlet and pop the pistons out. Remove the seals with a seal pick. Some say you can reuse the seals, but I think as cheap as they are, it's better to replace them. Clean the caliper cavities and clean any dirt or residue off the pistons. If you find any scoring or pitting on the walls of the pistons, then replace them as they will leak. Re-assemble. It may be a good idea to visit the brake master cylinder at the same time and at least clean and inspect the components. Recharge with new fluid, bleed, and your in business!
 
OP
OP
Joined
Dec 8, 2016
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3
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mckinney
Thanks so much for the reply, much appreciated. Just to confirm, this only happens periodically, so do you think that it is sticking periodically? A followup question, if the pistons in one of the calipers are getting stuck, wouldn't the brakes on the other side of the wheel brake ok? Again, thanks for your consideration.
 

Mark

Gotta make tracks
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Apache Junction AZ
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KTM 525exc
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3768
Sounds to me like something might be occluding one of the brake lines.
You might try to bleed the brakes in reverse (from the bleed valves at the calipers) sucking out the excess fluid before it over flows.
I'd also look under the little piece in the fluid reservoir and see if there is a bit of 'gunk' which might shift and block the opening.
 
Joined
Mar 21, 2016
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P.E.I., Canada
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2005 st1300
first thought that comes to mind is a worn master cylinder, casing the piston to "rack" and bind. If the 1100 is like the 1300, you have access to the end of the piston, behind the lever. Try pushing laterally , back and forth on the piston with a small screwdriver or pick while pulling the lever to see if you can replicate it.
 

wjbertrand

Ventura Highway
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Feb 8, 2005
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4,407
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Ventura, CA
Also check the condition of the lever pivot and the master cylinder push rod assembly (brass button with socket for push rod). Are any of the parts dry of lubricant or excessively worn?
 
OP
OP
Joined
Dec 8, 2016
Messages
3
Location
mckinney
Thank you so much for all of the responses. Some really good thoughts on things to check out. Very much appreciated.
 
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