brake pistons

[Dbarcle1@gmail.com]

I am rebuilding the brakes on my K100RS 1984 model and finding it very difficult to push the pistons past the new seal.  I use plenty of brake fluid to lubricate everything but there is resistance.  Any ideas?

[alexis291]

Are you sure you have the correct seals? Are they the same size as the original ones?
If you twist the piston as you push it in, it may go in more easily.


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[Laitch]

I use plenty of brake fluid to lubricate everything but there is resistance.  Any ideas?

Plenty—defined as heavy application—of brake fluid is not used to install a caliper piston, if that is your task. The slightest possible amount could be used on the piston and seal surfaces. Remove the piston, wipe the bore with a clean rag until the bore is dry. Is the piston surface clean and polished—not with abrasives, and without nicks? If it is, you should be able to align it squarely with the seals and push the piston slowly into position with equal thumb pressure on opposite sides of the piston's edge moving your thumbs around the edge until it is all the way home.

[Dbarcle1@gmail.com]

Hiya, thanks for the response about the brakes, the main problem was the parts I used from motobins, Ariete parts from Italy, the inner seal is wrong & won't allow me to push the pistons through with my thumbs, so I reused the old seals. I have complained to motobins & got a bit of a runaround but interestingly they have removed it from their site. Anyhow, all is well now. One more thing, one of my injectors is leaking. What parts do I need to purchase?  Is it the seals two for each injector?  Many thanks again for the guidance. Dave