SOHC.co.uk Forums > CB500/550
Front brake
bobv7:
Thanks all. Yep there was a bit of crud behind the piston and the 2 holes were free. What was more surprising was that the bleed nipple needed quite a bit of persuading to move even though I had cleaned and copper sliped it last time. Now brake fluid, DOT4 or 5? Good point about the seal, I'll check that too.
Bryanj:
Dont be tempted to reuse the seal as the sides deform to the crud in the groove which needs to be super clean, use a dental pick or similar not a dremel brush as the crud is so hard all the brush does is polish it.
Any pitting on the piston is bad, new stainless piston and seal about £30 on ebay.
Unless you can guarantee to get every last tiny bit of old fluid out dont use dot5.
I always warm the caliper before attempting to undo the bleed nipple and use a long 8mm socket with a tee bar so as not to stress it sideways as they snap off very easily
philward:
--- Quote from: Bryanj on November 05, 2020, 05:20:20 PM ---Dont be tempted to reuse the seal as the sides deform to the crud in the groove which needs to be super clean, use a dental pick or similar not a dremel brush as the crud is so hard all the brush does is polish it.
Any pitting on the piston is bad, new stainless piston and seal about £30 on ebay.
Unless you can guarantee to get every last tiny bit of old fluid out dont use dot5.
I always warm the caliper before attempting to undo the bleed nipple and use a long 8mm socket with a tee bar so as not to stress it sideways as they snap off very easily
--- End quote ---
If you are buying the SS piston and seal as Bryan suggests ebay seller), just check the edge of the piston isn't square as opposed to having a chamfer (compare it with the original piston) - I've had 3 or 4 of them over the years and the last 2 have been square - which wrecks the seal as you push it in to the caliper. I emailed the seller on the previous purchase and he checked his stock and said they where ok but the one I've bought (and not yet fitted) looks to have the same problem. It's not a big deal as you can chamfer the edge but if you don't you'll end up with a leaking seal.
bobv7:
Changing the seal but fortunately the piston looks OK. Lot of difference in prices being charged for 1L of brake fluid. ???
Bryanj:
Go to a local motor factors after Dec 2nd
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