CB550F Double Disc's

[Bryanj]

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!!!

[Ewan 500 K1]

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

[Trigger]

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

[Ewan 500 K1]

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

[Johnwebley]

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

[Bryanj]

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

[Ewan 500 K1]

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 ?

[Trigger]

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.

[matthewmosse]

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.

[Ewan 500 K1]

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,
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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.
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[Trigger]

Seems straight forward Ewan. Have loads of bolts in stock, was going to use some 110mm 8.8.

[Ewan 500 K1]

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 ?? )

[Trigger]

No rubber Ewan, looks spot on to yours. I think m8 x 110 high tensile steel bolts should be up to the job.

[Bryanj]

All i used eons ago, wing ones might be prettier as they are polished/chromed

[Trigger]

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.