XBR500 front brake problem

[xbruby]

Just stripped the front brake system and rebuilt using new caliper pistons and seals, braided brake line and new pads. After about half an hour of bleeding the system of air I secured the cover, diaphragm plastic retention plate and diaphragm using the two screws on the top cover of the master cylinder.
Front brake performace seems OK but I noticed that there is brake fluid weeping from a tiny slot midway along the side of the master cylinder cover. I took the cover, plastic retention plate and diaphragm off again and turned the diaphragm round in case it only seated one way. Made no difference, still weeping brake fluid when I pull the lever in.
Questions - 1) Have I overfilled the reservoir and is this an overlow/over -pressure leak path?
OR 2) is the diaphragm knackered (no obvious sign of damage) and can it be purchased for replacement OR 3) am I overtightening the screws?

Any help gratefully received and advice on improving the front brake performance would be much appreciated. Incidentally, I fitted the stainless steel pistons from Wemoto (I think they were recommended by Graham), a braided hose from HEL and Ferrodo pads.

Regards,

Andy

[guest295]

The only thing I can think of is overfilled. The level should be somewhere in the middle of the sight glass. That doesn't seem like much, but that's where it belongs. Overfilling can result in unexpected brake lockups.

[xbruby]

Yes, I suspect you are right. I filled it to the point shown in the XBR500 workshop manual but it seemed too full to me.
I ordered a new master cylinder diaphragm from David Silver this morning just in case. I wont use the bike until I am sure everything is OK with the front brake.
Incidentally is there anybody out there who has tried one of the Wemoto wavy brake discs on thier bikes? If so did it noticeably inprove braking performance?

Regards,

Andy

[guest7]

I've been meaning to buy some new diaphragms - did they cost much?

All mine have to be coaxed into position and the lid slammed down smartly to get 'em to sit properly

GC

[002]

I've been meaning to buy some new diaphragms - did they cost much?

All mine have to be coaxed into position and the lid slammed down smartly to get 'em to sit properly

GC

Re: Beaten with a large blunt heavy object !

Jethro

[xbruby]

£8.76 inc. p&p. Seems a lot of money for a a rubber seal but then again the bike is 21 years old so I suppose it must be taken in context. Will fit today (and remove some of the brake fluid for the resevoir) and report back.

Graham, have you tried wavy disks on any of your bikes?

Regards,

Andy

I've been meaning to buy some new diaphragms - did they cost much?

All mine have to be coaxed into position and the lid slammed down smartly to get 'em to sit properly

GC

[guest7]

Graham, have you tried wavy disks on any of your bikes?

Only the warped variety 

GC

[xbruby]

Fitted the new diaphragm last night - no leaks, good start! 

Took the XBR out for a 50 mile blast this afternoon, the improvement in braking performance is almost unbelievable  . What was shockingly bad  to the point of dangerous is now reasonably good. The front brake still lacks any real power when required but I am pleased with the improvement.

Next step the 'wavy' disk!

Andy
Obssesed with these smilies