Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: florence on March 23, 2010, 11:36:08 AM
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I have stripped my front brake and, yet again, the piston has gone rusty and needs replacing. This is something I have replaced about three times now, all for the same reason. Admittedly, I do ride my bike all year round so I'm sure the road salt doesn't help, but, does anybody know of a way of protecting the piston from the elements but which does not ruin the seal? I was thinking of, maybe, a silicon grease or something but do not want to experiment with something as important as brakes! Any ideas would be appreciated before I put the thing back together again.
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There's a guy on the US site who makes these from phenolic resin.
I believe that he buys Nissan parts and turns them down to the Honda spec.
Steve
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They do stainless steel ones for the 750, it might be worth try to find some for your 550, other than that regular caliper removal and regrease everything with brake assemley grease
Pete
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These guys have been recommended to me by several people, they don't list the 550 but they don't list a Scimitar either and they do pistons for them so they may be worth a call http://www.ssbrakepistons.com/
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Careful with stainless steel as some grades are attached by salt.
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I was surprised to not see a piston kit from these people... http://www.wemoto.com/bikes/Honda/CB_550_F_F1_F2/75-80/
But the OEM part shouldn't rust quickly...Dave Slivers do them http://www.davidsilverspares.co.uk/parts/part_62213/
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Thanks for that. I did order mine from Dave Silver and it's on the way.
I have found they rust all too easily. It only needs to be a small spot of rust in the working area and then I don't trust it. Maybe I'm being too careful?
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I replaced the piston in my CB750F1 with a stainless one from a guy on US eBay, the front brake piston for the CB750F1 are very difficult to source, I went the stainless route so I would not have to do it again. The back of the piston and caliper I lightly cover with silicon brake grease (from Brembo).
If there is rust on the contact area with the seal then it will not "heal up" so best to replace it
Cheers
Den
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Is the piston dust seal damaged on the caliper?
I thought that the piston for the 750F1 would be the same for the similar calipers on the 750K7, 550F1 & F2, 500T etc etc?
http://www.davidsilverspares.co.uk/parts/part_52251/
http://www.davidsilverspares.co.uk/parts/part_62213/
http://www.davidsilverspares.co.uk/parts/part_61411/
http://www.davidsilverspares.co.uk/parts/part_13841/
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Unfortunately the F1 front brake piston is different, I checked out the brakes on late CB750's and came up with a chart showing interchangeabilty, the K7 and K8 are the same piston but no one had them at the time I was putting mine together. The caliper itself is also fairly elusive,so I have a spare refurbisheed one in the loft.
http://www.sohc.co.uk/index.php?topic=1562.0
Cheers
Den
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That's interesting...i'd like to see what the differance is between the two types of pistons then. I wonder if it's just something like the dust seal groove in the piston, or a part that isolates the piston from the heat of the pad under heavy braking.
Wemoto do a stainless piston kit though... http://www.wemoto.com/bikes/Honda/CB_750_F_F1/76-77/
From what I can see from the pictures the internal part of the 750F1 piston is hollow, as against the solid looking item for the 250/400/500/550 Honda piston.
I reckon I can make a 750F1 piston if I had an original, together with a 400/500/550 one. I have my big lathe working now so this manufacturing this wouldn't be difficult.
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There was a similar thread on the US site
http://forums.sohc4.net/index.php?topic=66855.0
Probably worth a read
Cheers
Seamus
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Just looked through some of my old posts on this site and the US one and back then I also found a site that stocked brake pistons. You ordered by size rather than make and model, the one I got looked good but I went the stainless route instead.
There is a photo of the new piston alongside the original F1 piston in the thread as well.
http://forums.sohc4.net/index.php?topic=23037.msg244536#msg244536
Cheers
Den
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i just got hold of one of the phoelic pistons from Kevin is the us. that coupled with a reconditioned caliper and a new brake seal should see me right.
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Sounds good...
I put my caliper back together with a standard piston in the end. I then went to bleed the brakes and the bleed nipple snapped off which made me rather cross. However I have found someone who can remove them with acid which does not damage the aluminium. I don't know if others have heard of this and if it is useful? i expect you know about it already.
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Mate, sorry to hear bout the sheared bleed nipple.
Not heard about 'acid removal'
- I recently had a sump screw shear off, boy did I curse. I never had to fix one before. I used a dremel to dress the sheared screw, carefully drilled out 2mm,3mm using black n decker & 'easy-out' (drills & easy out from ScrewFix, &plenty of 3-in-2 penetrating oil. It does work.
Good luck whatever route you choose.
Andy C
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I may be wrong, but I seem to recall something on the US site regarding this. Does not sound right as aluminium would be more reactive than iron to acids/alkalies, but will have to do a search and find out a bit more.
Hate to say this but good luck with your nipple :o
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If getting the nipple out totally wrecks the threads do not panic but PM me and i will give you a link to a repair kit costing
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That is kind of you Bryan but I have ordered another banjo bolt with a bleed nipple in the top which solves the problem very well. This is in fact what I had already been using for the last twelve years and it was that bleed nipple which had eventually frozen in.
However, I put the chemical removal thing up for info really for people who want to keep their caliper original. A guy called Steve at Piston Broke Engineering in Bristol offers the service and he seems to be very confident about it. He did some excellent work for me a few years ago on my Indian and I trust him greatly.
I think it should be pointed out that trying to drill out a bleed nipple is rather difficult as you cannot be sure you will not to run into the base where the nipple seals into the caliper. Obviously, if this seal is compromised the caliper could become unsafe. The whole idea make me very nervous. At least if you leave the remains of the nipple in the caliper it isn't going anywhere and the banjo bolt/nipple option works brilliantly and, I think, is easier to bleed.
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Off topic, but
Be interested to see a picture of the Indian.
Cheers
Seamus
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Sorry, I don't have it anymore. It was a 1946 Scout 741 military bike which I rebuilt for a friend. It was rather strange, having a foot operated clutch, hand gear change and throttle on the left handle bar. I had it bored out to 850cc which was a massive job but worked well; we took about half an inch out of the liner walls. Steve at Piston Broke is a genius, he also did the rebore on my 500/4 back in 1995. He said he was going to bore it slightly tighter than Honda recommend and that if I ran it in very carefully I would get more miles out of it. He was right, fifteen years later and it still doesn't burn a drop of oil.
I don't have any photographs of the Indian, in fact, thinking about it, I don't have many photographs of my bikes past or present. I'm not really a photography person. I had to bribe my son to take the picture of my 500 in the avatar. I did do a before and after photograph of the cb500 when I built it but I don't have a scanner so can't publish it.
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For those interested I found the post again on the US site its:-
http://forums.sohc4.net/index.php?topic=13965.0
Since saying i havent put one under pressure i have used 2 of them on my Pug 405 estate calipers and they work perfik