Rear Brakes

[Martin6]

As you may have seen, I'm recommissioning my new to me, CB750K6. The ignition and carbs are now sorted, just some fine tuning of the carbs. On a 25mile test the bike did well and ticks over evenly (once warm).

Apart from a pilot light bulb and a very slight front fork weep, neither of which are urgent, the final thing on my current list is sorting out the rear brake. When I apply the brake I get a pronounced pulsing from the pedal. The brake is unusable. The shoes were replaced a few years ago and then the bike wasn't ridden. So they're effectively brand new.

I'm going to have a look at them this afternoon. I think there's a bit of a technique to installing the shoes, plus some force. Is it possible to distort the shoes when installing them? Is there a way to check? Any ideas on what else might cause the pulsing?

Thanks, Martin

[Nurse Julie]

I know that Trigger has had problems with DSS aftermarket shoe's, and check that the brake liner is not cracked .

[K2-K6]

As above noted, likey the drum is at least distorted such that a tight spot (closer to the centre) is being felt as it passes the brake cam point which has the most movement in terms of how far the lining material is moved toward the drum.

Generally checking for corrosion on interior drum surface, moutN wheel without brake plate and then spin it with a screwdriver or something similar held very close to the friction surface will soon show if it's out of round.

As Julie mentioned, they do crack the lining surface ring sometimes. May just show in spoke tension too, so check them as well.

[Martin6]

Hopefully this picture posts. A fair bit of rust and wear ridges. What do you think, beyond salvage?

The hub looks ok, the rim and spokes are recent and in good condition. Is it possible to get the drum re-lined? If so, any recommendations on where to go?

[Martin6]

The offending article 

[Sesman]

Yup, cracked hub. Repairable though.

[Martin6]

Yup, cracked hub. Repairable though.

Not sure on the terminology. Is that the drum liner is cracked? The outside part, the hub, that the wheel spokes thread through and holds the bearings / axle, I think that looks ok.

[K2-K6]

Yup, cracked hub. Repairable though.

Not sure on the terminology. Is that the drum liner is cracked? The outside part, the hub, that the wheel spokes thread through and holds the bearings / axle, I think that looks ok.

Terminology fine, it's the liner that's cracked and needs replacement.  Unsure who is doing this currently as there were some offering to repair, usually by using a car drum brake as source material suitable to machine to correct specification.

[Bryanj]

The problem you will have is that after you find a brake drum you can use you will probably have to remove the rim and spokes as the lathe to spin the 18 inch diameter wheel is kin big

[Sesman]

Deffo a strip down job. I know Trigger has repaired them with a new liner shrunk in, pegged and machined. He may not do them now, but I’m sure he will know someone…..

[Oddjob]

Didn't someone put up a link to a fella in South Wales who was doing these hubs?

Reasonable cost as well.

I sent the link to Roo but can't find it now.

[K2-K6]

Gap bed lathe to get them in if someone is doing many ( bit of the bed under chuck removable to get big dia in ) would avoid stripping wheel.

[Sesman]

Terry Ives?

http://www.sohc.co.uk/index.php/topic,23605.msg263653.html#msg263653

[Sesman]

Or Dave baker…

http://www.sohc.co.uk/index.php/topic,27149.msg250841.html#msg250841

[Oddjob]

Dave Baker Phil, cheers.