Hi all , want to replace the seals and pistons on my front breaks , anyone out there got a good write up on this ......is there a specific way these oil seals have to be fitted ????

 

when you strip the calliper,place a large sheet of paper out and put each bit down as you take it out so that you can put it all back in the same way(work on one calliper at a time), make sure that you clean out the recess for the seals but be careful not to scrape the metal away, use a plastic or wood scraper, tooth brush and loads of brake cleaner,pump the pistons out using the brake leaver if one sticks block the moving one with a bit of wood and keep pumping and the other piston should free up, make sure you get the pistons almost out on both callipers before you take out the first piston or you will be left with no means (unless you have an air line) to push the pistons out, just be aware that if you pump to far the pistons will pop out and cover everything in brake fluid, if you can get them almost out you should be able to pull them out by hand and keep loads of rag handy to mop up and catch spills
if your doing this job with the callipers still on the bike, get some plastic sacks and cover the wheel and mudgaurd up just in case of a spill.

 

The short answer is ........carefully, your life may depend on your workmanship.


It is not actually that difficult, the main things being scrupulous cleanliness, lubrication of seals and careful assembly.

To strip the pistons from the calipers I have found the best way is place a block between the pistons , wrap the whole thing in rag and carefully apply air pressure to the fluid input port of the caliper in short bursts , checking that all pistons are moving , in the case that one is stuck you can block/clamp the others and give that one a good puff. Once they are all moving you should be able to ease them out.
Dont be surprised at all the crap that has built up inside your caliper this is pretty normal.
The dust seals will probably tear as the piston comes out, remove the remaining section of the seal using a hook/angled type pick (a bit like a dentist but for a lot less money), now carefully hook out the square section seal from the groove inside the caliper.
Next you need to very thoroughly clean the caliper inside and outside, you can use a hydrocarbon cleaner at this stage but you must thoroughly clean all traces of hydrocarbon off using methylated spirits before assembly.
Now the good part,lightly lubricate the bore of the cylinder with brake fluid,making sure you get fluid into the seal grooves.Lubricate the piston seal with brake fluid andfit the seal into the inner groove.
Carefully fit the lubricated dust seal in to its' outer groove.Wipe the clean piston with brake fluid and then place it up to the dust seal, you now need to carefully draw the lip of the seal up the seal evenly at the same time wriggle the piston into the caliper gently easing it through the dust seal and keep wrigglig it in through the main seal.
The piston should slide into the caliper with only a slight resistance , if you have to push it real hard you have probably twisted a seal so will need to pull it apart and have another go at it(the good news is that if everything is well lubed you probably wont damage a seal if things go wrong).

Repeat this operatio for all the pistons and seals and by the time you have completed this you will have a good feel for how they slide together.
Now refit calipers and bleed brakes in the normal fashion.

Good luck it is easier than it sounds but is very satisfying to do the job yourself.
Regards
Kiwi JK

 

I've just done my right front caliper (sticking piston) and got the pistons out by leaving the hydraulics connected, leaving the pads in, sloooooowly pumping the brake lever until both pistons were up against the pads - the stuck piston would only move once the other was up against the pads - took one pad out, repeated, then took that pad out and used a paint scraper as the stop to get the pistons to where they were ready to drop out. No mess, no fuss.

My only issue with replacing the seals was I had *thought* that the fluid seal has an asymmetric cross-section, so has to go in the right way round or it doesn't work - this is from a caliper rebuild I saw on You Tube. Try as I might with my fading eyesight, I couldn't see one side wider than the other. Well, so far, I am not leaking fluid and the brakes work so I guess not all calipers have asymmetric seals.

The bleeding took a log time too: it must be a dark art I have yet to master.

 

Oscar
I have to admit that the local supplier of all parts "older Honda" here is a guy called Econohonda and the seals he has supplied to me for my and KiwiTK's bike have been genuine Honda parts,I like you cannot see any assymetricity in the seals and have just installed them as they came out of the packs with no problems at all.
eah bleeding can be a pain in the a--- I have found that sometimes you need to get as much air out of the calipers via the bleed nipples as you can then leave the thing sitting overnight and then crack the banjo bolt at the master cylinder and slowly pump the lever to get all the air out. Lots of rags etc to stop spills on paintwork.

 

Yup, lots of rags that's for sure. When I got the bike (about 5 years ago) I thought that there must have been a small (!?) fire , or overheating anyway, around the fusebox because the paint on the left hand side top panel of the bodywork is bubbled and crinkled (technical term) as if it had got very hot. However, I realised that it is right under the clutch master cylinder, so someone who owned the bike before me...