CB 450 twin. I said I needed a project

cardinal

Been Around the Block
Thanks for the idea. When I was bleeding the brake I could see that both holes in the MC were not plugged, is there another hole that you are referring to?

I am pretty sure this is related to the amount of pressure needed to push the piston into the caliper though. I just pulled it off again and the seal looks ok, there are some tiny nicks in it, but I think it's fine. When I installed the piston I could stand on it and it wouldn't move into the caliper. Using blocks and my bench vise I got it to seat, but it takes a lot of pressure to move it past the seal. It looks like the piston should be able to be installed by hand, right?
 

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pidjones

Over 1,000 Posts
Yes, it should fit in by hand. Did you lubricate it and the seal with clean fluid on installation? The rubber needs the fluid to lubricate it some. Otherwise, sounds like the seal is too fat or piston to large OD. Does it fit in smoothly without the sealing ring?
 

cardinal

Been Around the Block
Yes, it should fit in by hand. Did you lubricate it and the seal with clean fluid on installation? The rubber needs the fluid to lubricate it some. Otherwise, sounds like the seal is too fat or piston to large OD. Does it fit in smoothly without the sealing ring?
Yes I did use DOT fluid on the seal, and after taking it off there was residual fluid on everything. The piston does slide freely in the caliper without the seal. I think I may just order a new seal and see if it’s any better.
 

pidjones

Over 1,000 Posts
Make sure nothing in the seal groove. On seriously gunked-up old cylinders I use a small brass brush wheel in a Dremel. Could also be that you just got the wrong thickness seal. Can you compare it to the old one?
 

cardinal

Been Around the Block
Good thought, unfortunately the old seal is still stuck in the rusty old caliper. It was so bad that I just bought a new caliper. The piston is new too. I ended up ordering a new seal just to make sure I've got the right one. Should be here in a few days and we'll see how it compares.
 

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