Hitchcocks Forum

This is driving me nuts.
The bike is a 1998 500 iron barrel right hand gearchange.
Since fitting a nice shiny chrome back plate, using the original innards, when I release the rear brake after application, there is a CLANK, as if hitting the chainguard with a spanner.
It doesn't happen when the bike is stood still, I can make it happen by blocking up the main stand and turning the rear wheel and operating the brake pedal, but that stops me locating the clank.
The bolts that hold the brake shoe mountings are tight, I have just checked them today, as I have just had it in bits and changed the wheel bearings and cush rubbers, the torque nut is tight, the chainguard is clear of the back plate.
HELP.

As I’m new to my bullet, if this were one of my Airheads, is the brake arm well lubed? Could that be grabbing then releasing?

windmill john wrote: ↑

Sat Sep 28, 2019 5:07 pm

As I’m new to my bullet, if this were one of my Airheads, is the brake arm well lubed? Could that be grabbing then releasing?

Yes, all copper greased.

Is the brake rod hitting the pilion peg? Look at the clearance with the suspension both compressed and unloaded.

I have tried adjusting it very tight and very slack, it still does it.

Grab a decent mechanicing friend and get them on the back for a test ride and a listen

I can hear it very clearly, I even know roughly where it is, (backplate area), but I can't pinpoint it.
The sound is a sharp clank, no matter how slowly I operate the brake.

Worn brake cam, slipping round too far and the shoes springing back onto it? Not quite sure how that would happen, but it's all I can think of.

A.

Adrian wrote: ↑

Sat Sep 28, 2019 7:15 pm

Worn brake cam, slipping round too far and the shoes springing back onto it? Not quite sure how that would happen, but it's all I can think of.

A.

The bike is very low mileage, with very little wear evident, it has spent a lot of it's life laid up, so, I am changing consumables as preventative maintenance. I am thinking along similar lines, I wonder if I have installed the operating cam 180 degrees from what it was, and it has a ridge?
I'll pull it apart again tomorrow and get all forensic.

"Since fitting a nice shiny chrome back plate,"
That's will likely be the problem as that's what you changed. Just cos it's new doesn't mean it's OK. Especially with indian manufacturing. I'm guessing the bore of the back plate is binding on the spindle then releasing under spring tension and the clank is from the back plate. Could be the bore isn't perpendicular to the back plate causing the cam to bind?