Strange Rear Brake Problem

[Bob Kelly III]

yes he mentioned that a pot hole seamed to put the brake on for him as well , so more than likely the brake was just adjusted up a bit too tight !!!! probably only about 1/2" free play when the manual calls for 1" I believe..... I usually set them a bit more like 1 1/2" to 2"
however it would be nice to hear from him again to see if the brake adjustment was all that was wrong with it <GRIN> other wise I'll have to adjust my brake up and see if it does apply brakes at a bump ! LOL
Logically thinking the brake lever arm would be pulled a bit when the rear swing arm is compressed under load.... if the brake is adjusted up too tight that would apply brakes to the rear wheel ...when hitting a bump and compressing the swingarm.

Also, I'll try backing off the adjuster on the rod to see if more play solves the problem. But I don't like much play in my pedal, so that won't be a permanent solution for me even if it works.

..... he did say he likes his brakes set up tight....... !
.....I have an inkling that it may well be related to the rear swing arm movement like the rear swing arm bushings are shot or missing
Not sure about earlier models but Mine has plastic bushings in the rear swingarm and I expect they wouldn't last long on rough roads
......

Bob.........

 

[yamahadon]

Well, guys, I took a look at my brake linkage configuration today, and as many of you suspected, it was WAY out of whack. The arm on the brake pedal shaft was almost horizontal. When I moved it back to vertical, I had to rotate the brake pedal several splines on the shaft to get it back in the right poisition vis-à-vis the foot peg. It all makes more sense and seems to work better now. I haven't had a chance to take a test ride, but I'd bet my problem is fixed. Not sure how it got so hosed up -- I blame a previous owner "known but to God."

 

[5twins]

There's usually a mark on the pedal mount and one on the face of the pivot shaft .....

You align them and that sets the pivot shaft properly, or rather the arm on the back of it. Then you can properly set the pedal height (even with or slightly below the top of the footpeg) with the adjustable stop screw for that arm. Finally, you set the brake adjustment on the rod back at the drum. There are no marks for where that drum arm gets installed. You just need to experiment and find the right position on the spline so when properly adjusted, only about an inch or less of threaded brake rod sticks out the back of the adjuster nut .....

Once I find that ideal location for the drum arm, I like to mark the end of the pivot shaft with a Sharpie. I've pretty much lost count of how many of these rear arms I've seen around here improperly mounted. Even our usually very attentive DanielBlack has his off a spline or two, lol.

 

[yamahadon]

No mark on my pedal. Or grease zerk for that matter. Good idea, though.

 

[DanielBlack]

Even our usually very attentive DanielBlack has his off a spline or two, lol.

Here I am reading this thread with the thought going through my head that I need to look at this. It hasn't given me a problem, but I know I have more than an inch of thread sticking out. Thanks 5twins, yes, I'll take a closer look.

Edit, closer look of my current setup:

2nd edit, shifted the arm one notch:

 

[5twins]

Being one spline off can make a real difference. That looks very good now. There are many of these little "gotchas" on old bikes. Nothing that can't be set straight once you know how it should be though.

 

[yamahadon]

Final Report: Took a test ride today -- problem fixed. The old 650 once again is a joy to ride.

 

[yamahadon]

See my previous post -- configuration of brake linkage was way out of whack. Easy fix, thanks to input from XS 650 Forum experts!

 

[TwoManyXS1Bs]

To compliment 5twin's and DanielBlack's pics, here's the early 70-73 rear brake petal shaft fitment, with and without the securing nut.

 

[Bob Kelly III]

Ahh so that's where they hide the mark ! thanks 2M
....
Bob..........