Author Topic: 1976 550CB duel front disc conversion questions (Read 1203 times)

jjc · « **on:** August 27, 2023, 04:50:50 PM »

Yes, I know there are other posts on this subject, but I'm confused.

I have a second disc. It is actually my original which was replaced with a drilled disc. I can drill my original, so disc situation solved.

My questions revolve around what I don't have, where to get it/them & what has to be done to run the original speedo, which I would like to keep (as well as the tech)

I am new and tried to ask questions directly to a member, but don't seem to be able to. I'm sorry to have you have to go on again about my questions.

what do I have to do / machine, if anything, to my 2nd disc?
what do I have to do to my right hand drive parts? I would like to keep the drive on the right for the speedo
don't I just have to buy a 2nd caliper, pads, and mounting arm, reservoir with brake switch.
I will change over to braided lines on both eliminating the left tube and block and run a second line from a duel banjo bolt right from the new reservoir.

I will need a reservoir that can handle 2 disc (move enough fluid) also.

If any machining has to be done to anything, is anyone making the necessary part?

Shtonecb500 · « **Reply #1 on:** August 27, 2023, 07:40:52 PM »

https://www.dudley.nu/projects/CB550_dual_disc/

and this one
https://www.dotheton.com/index.php?threads/single-disk-to-dual-disk-brake-conversion-for-cb750.1525/

Shtonecb500 · « **Reply #2 on:** August 27, 2023, 07:46:16 PM »

use the links i provided for reference in the above posts. Your stock MC will work for dual calipers on our bikes, just update your lines like you mentioned. All you really need to make the mods is a hand grinder/cutting wheel, they are pretty easy. Just double up on all the parts with the brake system stock side, you will have to most likely space things out to ensure the caliper pads are square with the rotor, I usually use 1mm washers between the fork lower and the caliper arms to space it outward. you will have alot of back and forth figuring this all out for reasons you will figure out.

Have fun.

bryanj · « **Reply #3 on:** August 28, 2023, 12:07:45 AM »

Those articles keep coming and are both WRONG.

You need to look at your front wheel hub and see if the spigot on the speedo side has two flats milled on it or not then come back and i will tell you what you need

MauiK3 · « **Reply #4 on:** August 28, 2023, 07:27:17 AM »

+1 on stock master cylinder.
you'll have a little more lever movement but it works great, just need good brake lines.
I think the CB750s are the same in which case Yamiya will have the parts you need.

Don R · « **Reply #5 on:** August 28, 2023, 08:25:46 AM »

Scroll down to the double disc with no flats on the hub question. The answers are the same for 550 and 750. The stock M/C works fine, you just have more lever travel to move the pads. I'm working on a double disc myself, some guys use 550 double discs and caliper brackets on 750 because the rotor is slightly smaller and lighter.

jjc · « **Reply #6 on:** August 28, 2023, 10:33:38 AM »

OK, it was suggested that the enclosed links are wrong info & photos are needed, so I took 2. Is this what you need?

bryanj · « **Reply #7 on:** August 28, 2023, 04:49:44 PM »

Unfortunately not, it is whats under the speedo drive plate i need to see which involve removing the bolts and chrome plate, i have explained the differences many times but people still get it wrong so only way is to show me.
Under that plate is part of the hub that sticks out, a spigot, and there are two types

maxheadflow · « **Reply #8 on:** August 28, 2023, 09:44:24 PM »

While this is a CB750, the process is pretty much the same. Did my CB550F the same way years ago. Clamp the speedo drive hub in a lathe and machine the side so that the disc fits over it. 2 5mm flatheads to hold in place..

I cut the rivets on the fender and reverse the bracket and forks.

Don R · « **Reply #9 on:** August 28, 2023, 10:16:16 PM »

Like I said above, scroll down to this thread and see what you are asking about.

http://forums.sohc4.net/index.php/topic,193363.0.html

The part if you don't want to make it.
https://www.ebay.com/itm/295742330966?hash=item44db9dd856:g:cIIAAOSw92NhPGg~&amdata=enc%3AAQAIAAAA8DFIUNObcqHseHPk6J4qCF5n7zNhpuUJZ%2BP2hO8xiX6W3s1m2CeVNh%2BYZaXAb6DFQc7h1bdozwgmKV2CxvhW%2FMzIinQxpoqFYSRekYRV7NjeJYcY7hN7vMJMuLipgLiF%2FIaPYB40YJLhnCK%2B1sRZhKdifgVWTUagxcVAfFsHEZ9e%2FvNEYD3FxdZkOXPVFOKTizsh%2FwoW5wNiDZ7yhsHYTWCR9wBtOveVbtKy8PDrCCMKCMydZMeWjPT4YKtZFNRyVO%2FMe2dvJzoqOzgP0zWxzzmZSqE2G%2BRDLlGXJoWlzzMNAAIb0rTOsZKQwerFxOfUpw%3D%3D%7Ctkp%3ABk9SR76E4vvHYg

jjc · « **Reply #10 on:** August 29, 2023, 08:49:12 AM »

BryanJ
OK, I have stripped down my wheel as far as you can go.

bryanj · « **Reply #11 on:** August 29, 2023, 02:09:06 PM »

That is the later hub that needs the plate in the ebay link posted BUT put the second disc on first so as to centralise it better.

The articles are wrong because, as i have posted many times, you CAN NOT use the 500/550 plate as it is identical to the 750, you can use the CB750K0 plate again shown in a link above IF you have the hub with two flats.
In my humble opinion machining out two slots weakens the carrier too much PLUS you have to open out the centre to allow it to fit over the drive plate and this needs accurate lathe work and ruins the disc/carrier for any other use.

jjc · « **Reply #12 on:** August 30, 2023, 10:25:34 AM »

Where were the specs on the longer disc bolts?
I have to buy since there are none local. So directions on where to get them also appreciated.

38rudge · « **Reply #13 on:** August 30, 2023, 10:50:04 AM »

You will find that the front disc bolts used on the GL1000 Gold Wing will do the job. Don't know if they are still available new but when I did my twin disc I purchase a good 2nd hand set on e-bay.

You might find the following link, if it works, useful as it outlines how I did mine on my CB750K2: http://www.sohc.co.uk/index.php/topic,21171.0.html

jjc · « **Reply #14 on:** August 30, 2023, 09:40:25 PM »

Doesn't anyone know the length needed for two discs?
I know I don't need to maintain metric or the same tpi but to order I need to know a proper length. It would be nice to know the other data also so I can order w/o issue.

bryanj · « **Reply #15 on:** August 30, 2023, 11:37:36 PM »

8x110 ht bolts with nylock nuts, head end to speedo drive end

Shtonecb500 · « **Reply #16 on:** August 31, 2023, 05:04:42 AM »

srry bout posting those links, lol.

MauiK3 · « **Reply #17 on:** August 31, 2023, 05:11:30 PM »

I checked Yamiya, oddly they don’t have the bolts, they used to. Saw some on eBay

PeWe · « **Reply #18 on:** September 01, 2023, 07:45:51 AM »

My CB750 K6 has got that type of hub design on its latest wheel.
I use this one.

bryanj · « **Reply #19 on:** September 01, 2023, 07:56:46 AM »

Dont worry about the links, i have the odd bad day where reapeated myself makes me grumpy, and yes i have the sweatshirt from Disney

jjc · « **Reply #20 on:** September 01, 2023, 08:18:12 AM »

Ya, I'm waiting for my conversation part order to come through.
Thanks for giving me bolt specs . Then I will have to understand just what is left off when I add the new part

jjc · « **Reply #21 on:** September 03, 2023, 10:53:49 AM »

do I understand correctly that the thread of the 550 caliper inlet for the brake line is 1.25? Whats the dia? I want to order some brake lines from Speigler and they rate by an 'M' I believe.

bryanj · « **Reply #22 on:** September 03, 2023, 11:38:25 AM »

Its M10 but cant remember wether its 1.0 or 1.25, fairly certain it is NOT the common car one, Honda cars are the same as the bikes, or at least they are here in uk

Godffery · « **Reply #23 on:** September 03, 2023, 02:43:11 PM »

If you'd like; I can cam provide just about anything you'll need for Twin Disc, or even a complete bolt-on kit made to order.
https://www.instagram.com/p/CJFoMCEB4pF/?img_index=1

I can also modify the Calipers to mount Banjo fittings directly.
https://www.instagram.com/p/CXKnBWCsOiF/?img_index=2

jjc · « **Reply #24 on:** September 04, 2023, 09:04:19 AM »

I thought i posted this but I don't see it so - can anyone verify that the calipers brake line inlet is 10m

jjc · « **Reply #25 on:** September 05, 2023, 03:23:40 PM »

FYI
I asked earlier about the length / size of the necessary bolts to hold two discs. I was advised 110mm long. INCORRECT The length is 115mm.

jjc · « **Reply #26 on:** September 15, 2023, 10:10:24 AM »

OK
My conversation plate/part has come in,but I can't find info on what size these 2 little screws are so I can figure out what drill & tap to use.
Who has the screw info. All I have been able to do is gauge the tpi,which I find to be 36

Godffery · « **Reply #27 on:** September 15, 2023, 11:43:10 AM »

Quote from: jjc on September 15, 2023, 10:10:24 AM

OK
My conversation plate/part has come in,but I can't find info on what size these 2 little screws are so I can figure out what drill & tap to use.
Who has the screw info. All I have been able to do is gauge the tpi,which I find to be 36

That seems like a question for the suppler you got the plate from, but I use M4X0.7 flat heads for those.
Side note: When installed, Make sure the heads are completely flush, so they will not interfere with the Speedo drive unit.

jjc · « **Reply #28 on:** September 28, 2023, 02:52:14 PM »

Well, I have everything together but, I'm having problems bleeding the brakes.
Starting I injected fluid into each pod until fluid showed into the res. Then switched to a vac system. I now am doing nothing but cycling fluid w/o any air coming out. BUT, my lever is firm but not 'hard'. Meaning I can go to the grip, but the lever has pressure all the way.
So 1st question is - do these pots ever get hard / unable to touch the grip.
Remember I have a firm lever, but not hard & it goes to the grip.
FYI - I can see my pods slightly move each time I pull the lever.

I'm running two lines from the res to the pods by double banjo bolt with a Nisan 1/2" bore

robvangulik · « **Reply #29 on:** September 28, 2023, 03:20:36 PM »

Try riding (and braking) it, chance is that the tyre will be squealing before you pull the lever halfway.
If not, use the original 14mm master, 1/2" maybe borderline too small for 2 38mm calipers.

newday777 · « **Reply #30 on:** September 28, 2023, 05:45:10 PM »

Start by manually bleeding at the master banjo bolt to get the air lock out of the master(pump up 5-6 squeezes, hold and crack banjo bolt to release air and fluid, hold and tighten bolt. Repeat a couple more times. Then bleed each caliper. That should give you good lever and brakes.

News:

Author Topic: 1976 550CB duel front disc conversion questions (Read 1203 times)