Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Trigger on April 15, 2014, 07:55:05 PM
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Have a question that someone out on the forum may be able to answer. Fitting double disc's to a CB550, why does everyone state that you need a master cylinder with a larger reservoir? This reservoir holds less fluid than a standard cylinder but, is a replacement for a GL1000 with twin discs.
http://www.ebay.co.uk/itm/Front-Brake-Master-Cylinder-For-Honda-GL1000-GL1100-GL1200-GL1500-Handle-Bar-New-/321185608547?pt=UK_Motorcycle_Parts_13&hash=item4ac8277363
Could anyone explain who has done a disc conversion. Cheers
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I don't think it's because of the larger capacity, it's because the MC piston bore is a different diameter.
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it is due to the fact that you are pushing double the amount of pistons !! and double the amount of fluid,
the standard mastercylinder may not be able to fully extend the pistons,
so a larger bore M/C is required to ensure both caliper pistons are pressed on the discs with plenty of handlebar lever clearance,
apart from the equation of dia X volume = mech advantage etc,
to much blinding with science !!
yes,it is much better to get a twin disc mastercylinder,
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OK, now i am scratching my head, because i have measured up the bore size on the CB550 cylinder and it is 14mm. Matched this up against the cylinder on my CX500 (which is twin disc) and that is 14mm. I must point out that the cylinder on the CB550 is one of those aftermarket jobies from DSS and NOT OEM. Another confusing thing is a rear brake cylinder (though Japanees) states 1/2 inch, which is 12.7mm.
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Cheers Oddjob, that will explain it. All down to caliper piston size then. I will have to sit down and do the maths on this one, because the master in the link above states that it also has a 14mm dia. Trying to work out if the OEM master on the CB550 had a smaller dia piston in the master. ::)
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Right, just buzzed round a few forums and found a member that has just bought a aftermarket master for a GL1000K1 from DSS. He says that the master piston is 14mm. Had a quick look on DSS at the aftermarket master for a CB550 and the write up states that the replacement sohc master is also 14mm. Defiantly need to do some maths on this one.
John, you are right on the dia X volume but, i am thinking what would one need for a twin caliper set up? In the way of master piston dia.
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Right, just buzzed round a few forums and found a member that has just bought a aftermarket master for a GL1000K1 from DSS. He says that the master piston is 14mm. Had a quick look on DSS at the aftermarket master for a CB550 and the write up states that the replacement sohc master is also 14mm. Defiantly need to do some maths on this one.
John, you are right on the dia X volume but, i am thinking what would one need for a twin caliper set up? In the way of master piston dia.
I fitted a second disc to my CB500-4,using a standard caliper,and a GL1000 mastercylinder,,the feel is great,lever travel is as standard
with single disc,
and the GL1000 looks exactly the same as standard CB500
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If you look at Silvers the 550 and Wing master cylinders are the same.
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The first Wing had a master that looked identical to the 500 but had a bigger bore and the later ones had the clear, tall reervoir with a bigger bore ---I know for serpant as i got both in bits in my tool box!! No they ain't for sale, one of these days i am building a 605 with flowed head and big cam so will need the twin discs.
Many years ago when Girling still made things the started a range of japanese brake parts and i bought an early wing one, in my opinion it was a cosmetic reject from japan as the mirror boss flange had a slight dink that was anodised over
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Cheers for the input lads. It is all getting very interesting. After a few emails to part suppliers in the sates late last night and some Japanese this morning . Parts suppliers have stated that a master cylinder repair/service kit for a OEM, GL1000 has a 17.5 bore on the piston (well over engineered and could push any caliper piston) but, they all sell aftermarket replacement masters for the GL, 1973-1975 with a 14mm piston in the master.
Mailed DSS and asked what is the bore size on his aftermarket master for the GL 1000, lets see if it is different than the CB550.
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If you look at Silvers the 550 and Wing master cylinders are the same.
Just looked Lester and they aren't. They look identical but they have different part numbers plus the 550 does state it's a 14mm bore suitable for single discs whereas the GL version doesn't state the bore but does say it suitable for twin discs.
The part numbers only differ in the middle 3 numbers which I thought designated the model.
45500-410-000P and 45500-300-000P
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Oddjob, You can have identical Honda parts with different part numbers. CX500 had 3 different master cylinders: CX500/A had a round reservoir. CX500B came with a reservoir with 2 screws. CX500 Custom came with 4 screws. Now, back in the 90's we run out of CX500 Custom masters with a part number 45500-463-661 and found the CB250N was a identical part but, with number 45500-442-611. And at half the trade price.
We sat down and found a ton of parts by cross referencing on a microfiche. A brake lever for one Honda Model traded at £6.28. A match was found at £2.42. We also found a lot of interchangeable parts between Suzuki's as well.
The brake light switch which Honda RRP was £17.48 was made by ALPS in Milton Keynes. That switch would leave ALPS in boxes of 1000. Shipped to japan for packaging into Honda bags, Sent on to the european warehouse before been sent to the UK. I know how much that part cost to manufacturer. And it was less than the price of a box of matches.
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Well, DSS never came back wih a answer to the piston bore size on his aftermarket masters for the GL1000.
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I am not talking about looking identical. I stripped the master on a CB250N and measured up every part to get a match. The CX500 was launched with a single disc in some country's, though using the same master as we had in the UK for the twin disc.
Some parts have different numbers just because of the colour. eg: speedo cable eyes.
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Just had a reply mail from Karl at DSS. The question was could they tell me the size of the Piston bore size on the aftermarket master cylinder for the GL1000 part number ect,ect. Karl replied with: Thank you for your email inquiry. Unfortunately we are waiting for new stock to arrive so cannot confirm at this time.
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Master cylinder Confusion.
I thought i would have a look at the masters on the bikes i have in at the moment.
1998 CB400 master states 7/8"
2011 GSX-R 750 master states 7/8"
2006 CBR 929RR master States 7/8"
Everything started to make sence until i looked at the Honda Blackbird, the master is stamped with 1/2". So had a look at the CB900F5, that stated 14mm.
Now all these bikes have twin pot, twin disc. So still no wiser.
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Just had a reply mail from Karl at DSS. The question was could they tell me the size of the Piston bore size on the aftermarket master cylinder for the GL1000 part number ect,ect. Karl replied with: Thank you for your email inquiry. Unfortunately we are waiting for new stock to arrive so cannot confirm at this time.
the M/C I got from DSS,has bore printed on the underside, 15.8 mm.
http://www.davidsilverspares.co.uk/GL1000K1-GOLDWING-1976/part_126547/
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Cheers John, I think it is time to hit the pub because Honda state the replacement/ service kit is 17.5mm for the OEM master cylinder. Now are they talking about bore size or piston dia. I will drink my confusion away.
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Yes Oddjob, Totally understand that bit. But those spec are not available unless you strip it down. Lost count of how many brake levers i have taken off to hear a couple of washer's drop on the floor. One time i found a nut wielded to the piston.
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I think it is going to be a weekend of trying different Masters and using up my 5 ltr of fluid. Will try a 14mm bore and go up to a 7/8" which works out at round 22mm. Just to test the difference in travel.
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Really interesting reading about 'which master cylinder' (I've been considering the same conversion for my 550K3.)
But I also have another question.
What is the solution for the speedo drive with the additional brake disk??
do you have to machine the original to fit? or is there a speedo drive off a different model that fits the twin disk mod?
Andy C
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After some hours and circlip's pinging all over the place. As well as a load of emails to mate's that work in R&D for well known company's. The results were: If a master cylinder has 7/8" stamped on it. That would mean it is for a 7/8"=22mm handle bar fitting only :-[. Master cylinder's come in 4 standard sizes and on most modern bikes only 3 sizes are used and that excludes things like scooters.
1/2"=12.7mm Fitting ideal for rear brake caliper (single or twin pistons). Single front caliper (single or twin piston)
9/16"=14.28mm Fitting ideal for front twin calipers (single or twin pistons) General rule: production bikes over 250cc ( down to weight)
5/8"=15.8mm Fitting ideal for front twin calipers (single piston large capacity) and (multi small piston capacity)
11/16"=17.4625 Fitting ideal for front twin calipers (up to 6 pot double action caliper)
The orignal GL1000 master cylinder had a 11/16" bore but, was down sized to 5/8"
A common problem was found that not all master cylinders display a bore size.
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I am working from this:
http://www.salocal.com/sohc/tech/dual_disks/dual_disks.htm
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I am working from this:
http://www.salocal.com/sohc/tech/dual_disks/dual_disks.htm
that explanation/advice is so good,I hadn't found that,but its almost 100% what I ended up doing,
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John, What do you mean, nearly 100%?
I went with this guys advice because it was straight forward advice and the rest had turned there explaining into a book.
This link also says, No mod to the speedo drive.
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when I fitted the caliper mounting,I carefully filed the top T piece,so not to use washers as spacers ,other than that,
it was identical !!
this is my conversion
http://www.sohc.co.uk/index.php?topic=5572.0
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Cheers John, You had me worried a bit then.
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I was thinking the same things oddjob. Have not started it yet. Still collecting parts, Have 2 calipers and a disc from a CB500T. Was trying to work out the master.
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The theory about the fluid displacement being greater with a larger piston is valid. However, there are much more important things to consider. Like keeping the calipers' correctly adjusted, using pads with a higher coefficient of friction, using braided hoses, not leaving braking until it's more than too late, etc. etc.
And despite what logic might dictate, a narrow bore master cylinder (MC) piston (bike's stock part) will give a smoother and more subtle action when a second front disc is fitted.
Sure, the fluid transfer will be less with an 11mm bore compared to one of 16mm, by a little less than a factor of 2.16. but you'll have twice the breaking surface available.
You'll max-out the pressure in the breaking system (and hence breaking force on discs) before you bottom-out the break lever.
Track-day racers often use a "smaller than stock" master cylinder setup on their clutch for similar reasons, but in the opposite sense, i.e. they're feeding-in energy - not dissipating it.
So by fitting a second disc set-up using stock MC, you'll get a smoother braking system - not a stronger one. If you want a sharper braking system, just fit the MC with a larger diameter (say 16mm) and forget about the second disc/caliper/pipes, save weight at the same time.
Does the single disc set-up look as cool as the twin disc? Hell no!
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I am working from this:
http://www.salocal.com/sohc/tech/dual_disks/dual_disks.htm
that explanation/advice is so good,I hadn't found that,but its almost 100% what I ended up doing,
yep he's got it wrong about the unmodified spedo drive plate. The alternative to the one in oddjobs link is to modify the drive plate as per attached photo, ie cutting off excess and then bending over two tangs to fit the flats on the hub. Original drive plate on the right, modified one on the left. But.... this only works if have a hub with the flats on it, like the one in the second attached picture
[attach=1],[attach=2]
[attach=3]
Also , like oddjob, I fitted the mudguard stay between the pivot arm bracket and the fork tube .... didnt need to use any shims or file anything to get the pads sitting parallel with the disc
[attach=4]
I do still need to find a longer adjuster bolt as oddjob suggests
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Now I did my first twin disc using two 500 sliders which put one caliper in front and one behind and altered the muguard mount by carfully cutting off the psrt with the bolt holes , turning it round and welding it back on. Don't ever remember shimmng anything and everyhing worked ok.
Later rebuit it with a 550 sider when they came avaiabe used but still dont remember any shimming.
I bought a genuine part speedo drive as it is the very eary 750 one that is needed and have still got one NOS for one of my projects which i wi happily take pictures of and measure but not sell I also used a girling master for an eary GL1000 which was identical to the Honda part as this meant the lever did not travel so far back before the brakes worked.
All this was back in the 76/77/78 era so don't ask for any better descriptions, the only other thing i remember is finding out the steering stem was bent where it went into the lower yoke as when I used the brake hard the mudguard came up between the two centre pipes of the (Very Loud) Marvin exhaust system so no matter what you wanted to do you went straight on, as the IOM plod found out just before he dived over the wall at Glen Helen---I let the brake off and just got round, always hated my mates GS750 after that as there was no front brake operated brake light!!!
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Now I did my first twin disc using two 500 sliders which put one caliper in front and one behind and altered the muguard mount by carfully cutting off the psrt with the bolt holes , turning it round and welding it back on. Don't ever remember shimmng anything and everyhing worked ok.
Later rebuit it with a 550 sider when they came avaiabe used but still dont remember any shimming.
I bought a genuine part speedo drive as it is the very eary 750 one that is needed and have still got one NOS for one of my projects which i wi happily take pictures of and measure but not sell I also used a girling master for an eary GL1000 which was identical to the Honda part as this meant the lever did not travel so far back before the brakes worked.
All this was back in the 76/77/78 era so don't ask for any better descriptions, the only other thing i remember is finding out the steering stem was bent where it went into the lower yoke as when I used the brake hard the mudguard came up between the two centre pipes of the (Very Loud) Marvin exhaust system so no matter what you wanted to do you went straight on, as the IOM plod found out just before he dived over the wall at Glen Helen---I let the brake off and just got round, always hated my mates GS750 after that as there was no front brake operated brake light!!!
part number 44641-300-000, as shown ????. Think its unavailable now, but an be copied by modifying a stock 500 / 550 one as my post above
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Yes Ewan, had noticed it on your post. Was trying to work out if this bloke from Salocal put the drive plate in and then just crushed it by pulling it in by tightening up the disc bolts :-\
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Yes Ewan, had noticed it on your post. Was trying to work out if this bloke from Salocal put the drive plate in and then just crushed it by pulling it in by tightening up the disc bolts :-\
::)
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I managed to get the original speedo drive from CMSNL.com last year,
they had several in stock,
and I did have to trim the outer of it,and also file the disc carrier to take it
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Now you say that i remember having to take small amounts out of the disc carrier centre to make rectangular holes for the drive Tangs
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I suppose a Q for trigger would be ... what kind of front hub do you have ... is it the version with the two flats on it (see photo in my post above) .. or the version without the flats ?
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Ewan, I have the same hub as showing in your post. Oddjob, i was only joking about pulling it in on the disc bolts. You are right, how the hell did he do it without any mods? I think he was telling porkies.
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I did a twin disk setup on one of my cb550k3's many moons ago, I used comstar front wheel though so no usefull hints off that other than that I think I used a stock master cylinder, worked ok for a commuter, to be honest though I think a single disk works pretty well anyway - I coud lock the front tyre even with a sidecar fitted, the stainless disk was the thing I might change if looking for inprovement, but only during rain as I used to have to lightly apply the front brake all the time in a downpour if I wanted it to work immideately on demand. Once you master the mindset of doing it it was second nature to keep light braking pressure on 200 yards before every bend or blind spot. I do know that my bmw of the same era had the same issue, though less as twin disked and drilled from the factory and for these you could buy pfm performance disks which being cast iron looked horrid at the mere mention of rain but gave better braking. I had a set but never used them.
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Ewan, I have the same hub as showing in your post.
Then I think you just need to make the one on the right into the one on the left,
[attach=1][attach=2]
CMSNL are out of stock of the original part http://www.cmsnl.com/products/retainer-gear-box_44641300000/
Mount the mudguard bracket BETWEEN the fork and the brake pivot arm bracket and you wont need any shiming or shaving. You'll need some goldwing disc bolts. Less sure about the master cylinder , but I had a goldwing one (retangular kind) to hand anyways so used that.
You might also find that the speedo cable rubs off the new disc so will needd to do summat about that.
[attach=3]
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Seems straight forward Ewan. Have loads of bolts in stock, was going to use some 110mm 8.8.
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Seems straight forward Ewan. Have loads of bolts in stock, was going to use some 110mm 8.8.
Maybe need to be Jap spec for smaller diameter head size (12mm ) ... or was it a shallow enough head depth to allow the bolt heads to clear under the speedo drive ... was one or the other or maybe both ;)
.. also was advised not to use stainless bolts as they cant take the shear stresses
John W did a conversion recently and had to do a bit of shimming ... but think he mounted the mudguard braket ON TOP of the pivot arm bracket ? .. also (strangely ??) John had to take some material off the disc to allow the standard 44641-300-000 speedo drive plate to fit. I never had to do that to my modified one.
Also, there's two versions of the speed drive plate that has the lugs that fit in the chrome cover ( ie the one I modified). One is solid and one is a two part one with the two parts joined with rubber. I used the former to make my equivalent 44641-300-000.. if I recall correctly I seem to remember seeing somewhere that you cant use the two part one to modify to a 44641-300-000 shape (maybe because the heat from the grinder would melt the rubber ?? )
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No rubber Ewan, looks spot on to yours. I think m8 x 110 high tensile steel bolts should be up to the job.
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All i used eons ago, wing ones might be prettier as they are polished/chromed
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Sorry Graham but your wrong here. If the parts were identical then it would have the same part number, there are NUMEROUS examples of Honda using the exact same part on lots of different models but they still kept the original part number. There are websites dedicated to cross referencing part numbers, showing all the models that part number was used on. The 250N master cylinder was a single disc MC not a double disc, if you look at the 400N (45500-443-614) which did have a twin disc setup it didn't use the same part number as the 250N (45500-442-612) yet they would have looked identical, yet they were designed to do a different job. So it looks like you put an MC onto some CX500 which if they'd had been in an accident, and it was blamed on the wrong one being fitted, you'd have been liable :)
I'm not saying that sourcing where the parts were manufactured originally means your wrong to fit them as they don't have the Honda part number on the bag, clearly they are the same part, as such they are fine to fit. However it's wrong to assume that just because a part looks the same as another it's the same part with another part number, Honda just didn't do that, especially in the 70s.
I took on board what you said about part numbers would mean it was a different part but, i have 3 fuel tanks sitting in front of me: a CB550K3, part number 17500-404-670, a CB550F1, part number 17525-390-000 and a CB550F2, part number 17525-390-708. I have removed the paint code from the part number. All these tanks are identical in every measurement and shape.
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They are identical in shape but are the stripes and badge fixings the same?
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Now you are getting it Oddjob. Yes, the tanks are identical apart from what is added to that part to give it a different part number. The only difference in the master cylinders was the brake light switch. And i think it was down to the manufacturer of the switch. One was made by Alps and the other by Mitzubi. Nothing to do with the bore size of the master cylinder ;).
Engine parts are another story.
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Oddjob, you mentioned the 400N up against the 250N, not me. I was on about the CX500 custom. The part number for the piston/seal kit is different between the CX500C and the 250N (i can't explain why) But, as you say the piston may be longer.
All i can explain is we fitted the 250N to the CX500C with no problems.
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I thought one nice solution might be found on the bavarian wheelbarrows from the 70's, they put the master cylinder (easily capable of moving sufficient fluid for twin disks with big pistons - one of mine is running gt750 kettle calipers) anyhow, the actual master cylinder lives under the tank, with a cable operating it from the handlebars so you could get a much cleaner look to the handlebars. I think the gt750 calipers would probably have very similar fluid requirements to cb550 dual disk which work well of this setup, even when asked to stop a heavy bike, 100 kiloof sidecar and 4 adults riding said contraption (with a drum rear brake on the bike - no brake to the chair so lots to ask of a dual disk setup) Just a thought.
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Your confused Oddjob. I haven't a clue what you are going on about Mat. Are you farming magic mushrooms? ;) Have seen a wheelbarrow with a brake but, that was in Bulgaria and Albania. Never seen one in Germany.
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Bavarian wheelbarrow - a rather odd nickname for bmw aircooled boxer twin motorbikes, sorry, a bit obscure.
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I thought you was on about this type:
http://www.youtube.com/watch?v=bqzu1_NqK_Y
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could have been a Moldovian washing machine
http://www.youtube.com/watch?v=sMYRf5Ap72k
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I don't know who first refered to bmw boxer airheads as bavarian wheelbarrows, but for me that is what they will always be. They handle really well but boy are they an aquired taste looks wise and I found them disappointing quality / cost wise after a honda sohc4. I'm afraid being out in the sticks I may get better riding roads to go to work on then most but I cannt view the vids, just a plughole of doom loading icon.
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This may help you Matthew. http://download.cnet.com/YTD-Video-Downloader/3000-2071_4-10647340.html
Lets you download and save youtube vids.