Ooze from brake nipple plus drip from handlebar CM400 1981

[Windmill John]

Okay, I’ve cleaned the caliper, new pads, fluid etc, but fluid still slowly climbs through the centre of the nipple.
I know it will be the seat beneath the nipple and I’ve tried reaming it with a cloth and cross head screw driver. I will try a pencil next, which worked on a float needle seat in the past. I have fitted a new nipple. I may try and clean up the old nipple and retest. If I could find a replacement caliper, then great. Unless anyone knows a great fix for the seating?….
I went in the shed and found a drip on the floor beneath the master cylinder. I’ve already fitted a new o ring beneath the cylinder. No question here really-ish. I’ve put a tissue beneath the cylinder and if it’s coming from the piston, then obviously I’ll replace. Actually a question. Is anyone aware of a replacement master cylinder in the UK?

 

[LongDistanceRider]

Sounds like the bleeder seat of the caliper is dirty/corroded. Q-tip with lapping compound on a drill should clean that up.
Banjo bolt washers not sealing??

 

[oldjeep]

Or the crimp on the hose could be leaking.

 

[oldjeep]

Master Cylinder Rebuild Kits | Precision Components

Fix leaks and restore optimal hydraulic pressure using our complete master cylinder rebuild kits. Everything you need for a smooth and safe installation.

brakecrafters.com

Have a look here for rebuild kits. I buy most of my master/slave/caliper rebuild kits from them regardless of what the bike is

 

[Windmill John]

Thanks all. It will be the seat. There was some ooze originally from the threads, but this just comes up the middle. Takes an overnight to reach the top, but that’s without using the brake.
Cotton bud plus lapping compound sounds like a plan.
Re master cylinder, if there’s a drip tomorrow, then I’ll go the rebuild route.