Honda-SOHC

So, I have now completed the brake re-build. Actually bleeding the brakes was not the drama I was expecting and after a few false starts to get the fluid flowing I seem to have been able to get all the air out and the brake seems good and firm when applied, with about the right amount of brake lever play. I will leave it until tomorrow and re-check to see if any more air come out but I am not really expecting any.

Because of the brake binding issues which started this all off, I have very carefully rebuilt the whole caliper bracket and hinge pivot assembly, which now seems much better and swings nice freely before I fitted the callipers. I have adjusted very carefully the caliper adjusting bolt so the fixed pad just drags slightly, then backed it off half a turn (as detailed in the workshop manual), so the wheel spins freely.

However I note that when I apply the brake and then release it there is still a little bit of drag on the wheel - its nothing like what was previously experienced, where the brakes really seemed to bind, but it is still there. Is this normal, particularly with new brake pads or is something still not quite right.

So the brake saga continues!

I have received my new replica Brake cylinder from DSS - looks very nice and have fitted it.

Once fitted I was able to pressurise the system and force out the piston from the wheel cylinder (I has suspected that some of my brake issues were down to the pad itself not moving back when the brake was released and therefore binding on the disc). I found that the pad itself was almost held in place by awful looking 'gunk' and would not slide easily on its own.

I am replacing the pads, but does anyone know if the build-up of any sort of 'gunk' around the pad is normal and should there be something to stop it? (I have seen on the packaging of the new pads that it is recommended that they are removed and cleaned every 3000 miles, which doesn't seem a lot, but there isn't any mention of this in the Honda workshop manual I have, nor the Haynes manual).

I have also read about using copper or silicone crease behind the pad but have assumed that nothing should be smeared around the edges of the pad to ensure that there is no possibility of any grease contaminating the pad surface or the disc itself. Any thoughts on this?

Also, does anyone know the mechanism that causes the pad to release once the brake handle is released - is it actually pulled back by reverse hydraulic pressure or is it just naturally pushed away from the disc by its rotation (I know from the manual that the spacing between the pads and the disc is meant to be pretty small (just 0.15mm)!

Umm -doesn't sound to good to go ahead with the master cylinder I have - does anyone have a puka 550 one that they would like to sell? I obviously have a suitable re-furb kit for one so could apply that if it was required to bring the cylinder up to scratch.

Hi All,

Thanks for all the input.

First to dimensions - here they are. The critical diameters are identical (even though the pictures might suggest otherwise), although there is some slight difference in the lengths. The parallel part of the seal is about 13.5mm dia so should fit in the bore without a problem. It is also comparable with the first part of the original one, before it expands out). Just as an experiment to test this I turned the piston around and put it into the cylinder the wrong way round, so that I was not pushing 'against' the flare and it does go in OK!

I have looked at several different rebuild kits supposedly for the 550 and some show the 'flared' secondary cup but others (notably cmnsl) show a cup which is the same as the one I have removed - can they both be correct? I have also seen at least one suggestion that there are two different sizes of kit and one of them is wrong but don't know if this is really the case.

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As to the question - is this really a 550 master cylinder, here are some more pictures. Carefully comparing these with the workshop manual and other pictures on line I would conclude that it is but am happy for more expert opinion - This is how the bike came to me, but of course it is possible someone has changed it in the past.

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So, Master Cylinder re-furb kit has arrived, but putting it all back together is not going smoothly!

Everything in the kit looks pretty much identical except the Secondary Cup - this came already fitted to the Piston, but it looks slightly different to the original with the end of the cup being more flared. (see Picture). Overall at the very ends it is about 2mm larger in diameter.

Although softer than the original I just can't seem to get it into the Master Cylinder Body!!

Has anyone any experience of this - is it possible its the wrong kit? (although purchased from David Silver against the right bike model!). I maybe could just force it in (say using a vice) but this seems a bit extreme.

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Thanks - that worked fine.

One (hopefully) last question for now....

The reservoir has two small holes at the bottom (see picture). The one on the left is clear and goes through into the bore of the master cylinder body but the one on the right seems to be a blind hole or is very firmly blocked. Should it be clear or is it not really a hole with any purpose? If it should be clear how do I clear it (I have tried a very fine piece of wire but if it is blocked the wire can't shift the blockage!). [ Guests cannot view attachments ]

I have had some issues with the front brake on my 550 so have had to look at the master cylinder.

Unfortunately (as commonly seems to be the case) the internal circlip was badly rusted but have managed to remove that. I was then expecting the whole internal assembly, piston, cup spring etc to simply come out or at least come out with a gentle push from hose connector end, but it seems locked in place.

Should they simply and easily come out or have I missed something else which needs to be removed first? is it possible that perhaps the washer under the circlip has rusted and this is causing the problem? If so how much pressure is it safe to apply to help it out (I have already applied some easing fluid which help release the circlip)

Thanks for any help - would like to get the bike roadworthy again very soon!