rear brake sudden lock up

[Guest]

the rear drum brake on my 81 gsx400 locked up on me this morning, causing me to go down. When I pressed the brake peddle it did not engage the rear brake when it normally would have. Instead the rear brake activated suddenly as I continued to press the brake peddle, and when it did engage it braked very hard.

What is wrong with my drum brake?

thanks
BentRod

[bonanzadave]

Hope ya didnt go down too hard.....

I didnt see a 400 in Bikebandits parts diagrams, only 450s. Youll have to take it apart. Could have had a brake lining come loose and jamb it up.

[Steve]

The adjustment nut on drum brakes has a curved sleeve that pushes on the linkage. If that is not seated fully when you adjust the linkage, it can move on its own, and could conceiveably cause strange things to happen. However, I do not see the probability of it jumping on its own to the point where it will cause the brakes to lock up. It would more likely release them suddenly when you have them applied. Consider bonanzadave's suggestion that there might be a loose lining inside.

.

[Suzuki mad]

Recently was working on a GS(X)400 twin with drum brakes. Found that the inner part of the drum was not circular so the shoes only touched at part of the revolution.

Suzuki mad

[BentRod]

I was applying the brakes at the time.
the road was wet and oily, hence I lowsided the bike

rear brake is same on 400 as 450

[SqDancerLynn1]

I would check & make sure the pedal moves freely- no rust on the pivot
Brake torque arm- still hooked up. Next is to dissemble it...

[flyingace]

BDave is right. The only way to know for sure is to expose the brake unit. One possibility is a lining so badly worn or a bent shoe such that when the leading shoe (if it is a leading shoe unit) gets close to the drum, it just jams into place instead of progressively increasing friction.