Back tire on motorcycle keeps locking up.?

When I first fell on my bike I took it to a local motorcycle shop and found I had air in both brake lines, they bled both lines and put new fluid in them. As they were delivering my back to me the guy nearly wrecked from the back brakes locking up on him, took it back and re-bled the lines and no problems since.

When I first fell on my bike I took it to a local motorcycle shop and found I had air in both brake lines, they bled both lines and put new fluid in them. As they were delivering my back to me the guy nearly wrecked from the back brakes locking up on him, took it back and re-bled the lines and no problems since. The other day as I was driving, using both brakes, my husband and I were coming to a light and I started to slow down, the bike seemed to bog down so I turned onto a street to get out of traffic and as I got closer to complete stop the bike tire just completely locked up. The mechanic showed up and released some air again from the lines and drove it the shop with no problems. There are no holes in the brakes line and no fluid leaking. As I took it back home without using the back brakes, the tire locked up again. I took it back to the dealership and they can t find anything wrong other than someone had messed the the "tension" I think is what they called it, to the back brake peg. They also test drove it, on the highway when I specifically told them city traffic, and did not have it occur to them. What can cause the back tire to lock up if there is no holes in the brake line and not even be using the back brake?

Other answer:

Kayla:
Rebuild the master and slave cylinders, and blow out the lines to make sure there's no goo in 'em. A common problem is corrosion inside the cylinders, which you'll see whenya rebuild 'em. A home mechanic can usually do it with a rebuild kit (which consists of o-rings and seals) and a bit o' scotchbrite and solvents, like brake cleaner (guess what it does, babe), soapy water, and a kitchen sink and an old toothbrush (so high tech). There's even YouTube vids. Buy a Haynes or Clymer or factory shop manual if you want written directions, but here it is in a nutshell: disassemble; clean; install new seals; reassemble. Lube the new o-rings and seals before ya stick 'em in. Like totally rocket science, eh? In the alternative, pay someone else to do this extremely easy job for you. Oh yeh… and ya gotta have a basic metric tool set, and know lefty loosey, righty tighty, and how not to strip stuff. On second thought, take it to a better mechanic.
guardrailjim:
Might need a new master cylinder or a master cylinder rebuild kit.
When you press on the brake pedal, brake fluid is pumped to the rear brake caliper and the brake pads are pressed against the brake rotor (disc).
When you release pressure on the brake pedal, the pressurized brake fluid returns into the master cylinder.
The master cylinder return ports might be restricted (due to infrequent brake fluid changes), or the piston that pumps the fluid out of the master cylinder is preventing the brake fluid from returning.
When the mechanic "released the air" he was in fact releasing the pressure of brake fluid forcing the brakes on.
Air in the brake line would cause the brakes to not stop at all.
Since the brakes were locked on, there was no air in the line.
Bring your bike to a competent mechanic.
Joe:
I had TWO Hondas that did this with the front brake.

Your "mechanic" needs to find a job. They are B.S. ing you because they don't know what they are doing.
There is no "air" in the line, he keeps bleeding it to let the pressure off of it.

What is happening is that your master cylinder or caliper has shiit in it, and it slowly builds pressure that can't be released all the way because of the crud. It does that via vibrations, road bumps, ect. you don't have to pull the brakes for it to slowly (or not so slowly) lock up.

Clean/rebuild the caliper and the master cylinder, and FIRE THAT MECHANIC!

Peter H:
By now I would seriously question whether it was the brakes at all. I think it is more likely that you have a serious problem with the chain and chain sprockets. Certainly you need a different mechanic: I would not trust that lot any further.
fuzzy:
Geta Beta mechanic
Tim D:
If anything air in your hydraulic lines will cause the brake to not lock up or function properly at all. The obvious symptom of air in your lines is a spongy feel at the lever (or no pressure at all).
Candid Chris:
Your 'unknown' POS bike has problems and you and the mechanics working on it have more problems.
Find a pedal-bike, you'll be safer.
rick29148:
Sounds like a bearing is going bad on the rear axle….
adam:
i f there was air in the line the brake would NOT work. Its dirt . Take apart and clean!

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