Topic: K7 rear brake behaviour - is that normal?

[Erny]

I removed rear wheel, just before took photo how chain is adjusted - you can see really new.
Also measured tickness of shoes. For me good. Unable to measure drum precisely but looks like 180mm, surely less than 181. So also OK.

And measured angle of braking arm line trough axle hole and breaking rod hole. It is approx 37 degree. I think the only way to make breaking arm more to 90 degrees is to rotate it on bolt, ignoring punching. Adjusting pedal will not change anything...

[brewsky]

While doing first testing miles I realised unexpected behaviour of rear brake.
When braking on flat surface no issue, it brakes really perfect, fluent, high power.
But when braking on bumpy surface, brake pedal is moving up/down, braking is not fluent, I feel as brake drum is very oval...it blocks wheel easily

I also realised when doing setting of brake that all is OK when bike is on main stand, but when I put bike down from stand and sit on it, rear brake is braking!

Lookig at brake, wondering is that normal? I can imagine it is not very safe braking. I'm maybe oversensitive to it as I don't have front brake now (waiting new hoses to arrive).

ERNY,

Going back to your original question, I have essentially the same bike, and have put over 46,000 miles on it, and the symptoms you describe are completely NORMAL.

I believe you had the answer to the symptoms, when you said YOU may be overly sensitive, since you were riding with ONLY THE REAR BRAKE now.....that would certainly amplify any rear brake feedback and make braking on bumpy surfaces even more prone to skidding.

If you adjust the rear brake on the centerstand, it WILL tighten up off the stand, and under load.....it has happened to me also.....again, it is normal.

As others have said, the only brake "problem" you appear to have can be corrected with a simple rear brake adjustment.

Simply raise the pedal rest position as much as you can with the adjustment bolt,....THEN do the rear brake arm adjustment with the bike NOT on the center stand, and..........PROBLEM SOLVED..(after you get the front brake working!)

All the other discussion about arm lengths, pedal appearance, arm angles, etc, are not the problem....as they are the same as mine.

I believe some answers do not reflect that there is considerable difference between earlier models and K7&8.

As to the chain length issue, I did the exact same as you....ordered an 88 link replacement (only not endless) without counting links on the old chain...only to find it was only 86 links! You will probably need to cut off the extra and get a master link, as I did.

With only 9,000 miles, you have essentially a new bike.....adjust, ride and enjoy!

[enwri]

Do you need to push it that far in normal use? I get about 2 inches travel,
My wheel locks up before pedal gets that far.

If I adjust my brake too tight on the centrestand, it will drag when on its wheels. One turn out stops it dragging.
The geometry at the front end of the lever is as good as it can get. To have perfect geometry and not pull, it would have to be pulled from the centre of the swingarm pivot, it's not, it's about an inch lower. Wheel goes up, brake gets pulled, not much, but with bitey brakes, will make it chatter over bumps on hard braking.
 Hydraulic discs make the whole issue redundant.

[Yamahawk]

Erny,
   In the 3rd picture, the lower brake shoe seems to be missing a chunk of the lining. Do you know in these are replacement shoes, or are they the original shoes with 9k miles on them?
IF they are the original shoes, please consider replacing them with a good set of NEW shoes. The problem, is safety related, as old brake shoe linings from the '70's will delaminate and separate from the backing metal of the shoe, and then all #$%* breaks out when the lining wedges itself into the other shoe, and locks up the rear brake. THIS IS IMPORTANT! You do not want this to happen. For the price of a good set of shoes, your life is worth far more than that.
Charlie

[enwri]

Erny,
   In the 3rd picture, the lower brake shoe seems to be missing a chunk of the lining. Do you know in these are replacement shoes, or are they the original shoes with 9k miles on them?
IF they are the original shoes, please consider replacing them with a good set of NEW shoes. The problem, is safety related, as old brake shoe linings from the '70's will delaminate and separate from the backing metal of the shoe, and then all #$%* breaks out when the lining wedges itself into the other shoe, and locks up the rear brake. THIS IS IMPORTANT! You do not want this to happen. For the price of a good set of shoes, your life is worth far more than that.
Charlie

+1 as above, you think they bite hard now, wait until a chunk breaks off and jams in.
I've just taken a photo of my pedal with a lighter jammed under the adjuster. That is enough travel to lock it up solid, can't move the bike, stalls out, would burn the clutch if I tried any harder. never gets that far down when riding. Fix your front brakes quickly and use them.  Sorry about the sideways photo...

[brewsky]

Those shoes look good to me, don't see any sign of delamination or missing chunks.
I wouldn't hesitate to use them if it were me...jmho

[Yamahawk]

Those shoes look good to me, don't see any sign of delamination or missing chunks.
I wouldn't hesitate to use them if it were me...jmho

I can't tell for sure, but at 7:15pm on the lower shoe, it looks like a chunk missing. If not, it still doesn't matter if the shoes are the original ones from 1977. If they are, that means a 41 or 42 year old brake shoe, and it isn't if but when they separate from the backing plate. 
I err on the side of caution, after removing many drum brakes from the drum, only to find a lining laying in the drum still. I had one from an RD350, come loose as I was riding, and as it drastically slowed the bike, I nursed it home, disassembled the rear brake, and found pieces of the lining wedged in the brake. Not good.  So, I recommend automatic replacement of brake shoes from a bike with original brake components that are dated as these bikes are, and also for the front pads, if original. The glue used back then has an expiration period, I do believe. And really, for $40 or less, you can have peace of mind, and safety in your brakes by just replacing the shoes if original.
The problem with drum brakes, is that you CAN'T see them. They are fully enclosed in the drum, and aren't visible for inspection, as you ride, and so you never will see them gradually delaminate.
Really, it's your call Erny, but imho if they are original. and not replacement shoes, replace them. If you only have 9,000 miles on that bike, it is consistent with the wear you have on those shoes.
Charlie