Dual Disc Conversion

[cb550k-aaron]

Hi guys, I'm sure this has been covered before but I literally can't find it in the search the answer I need.

I have a 1978 CB550 K3, I'm doing the Dual Disc setup. Both forks have exactly the same mounting positions and dimensions all the same. If I put both discs on my Hub which is Asymmetrical, so the RH disc sits 3mm Closer to the Spokes, from outer edge of the Disc to the other is 124mm. (I always thought a 3mm spacer might be needed.

Now on my calipers the measurement from the inner edge of the Piston side to the other piston side on the LH is 124mm.

Does all this sound right or should I be using spacers on the mounting points or what? I have the Mudguard bracket on but it's on the outside of the caliper bracket ATM and not inside next to the fork. I obviously don't want to be pulling the lever and ending on my head first time.

Thanks in advance

[Johnwebley]

   I have a dual disc on my 500 ,using a later RH fork lower ,

  not sure of the various measurements ,but it went together OK,no spacers needed ,
on the RH leg,you may need to check the mounting lugs are nice and flat for the Tee piece to mount on,
 my thought being the leg will not have been machined as no 2nd disc was fitted  .

 how are you doing the speedo drive ?

  and it is a worthwhile mod

[cb550k-aaron]

Hi mate that's good to know.

I have the hub that makes the RH disc sits 3mm closer to the Spokes than the other side. That's why I thought I'd need a spacer. When I married it up today the two Brackets were in the right area so I'm at a loss tbh. Maybe I don't need a spacer at all.

For some reason my front guard bracket won't fit on the inside closer to the fork. It sits on the outside ie the caliper bracket on first then this.

[kevski]

When i done my 500k3 i had to machine down part of the speedo drive as it fouled on the disc, aside from that and just a new master cylinder every thing else was straightforward.

[Erny]

Thinking about dual disc setup too, both on my 550K1 and 750K7

Can you recommend somebody who makes/sells modified speedo drive?

Note: I suppose stock bolts can be used to fit 2 discs? Or do I need to replace them too?

[Bryanj]

Longer bolts and a man on the US forum does a speedo drive but it isnt dificult to modify yourself as long as you have the hub with milled flats on the raised bit of hub.

[Erny]

As non natural english speaker I do not understand "as long as you have the hub with milled flats on the raised bit of hub."

Any photo available that can explainit?

[Bryanj]

The centre of the disc fits over a raised portion of the hub. Earlier hubs are not completely round but have two flat sides oposite each other, later hubs do not have these. I think there is a picture in the genuine Honda manual, i do not have a picture nor access to getting nor posting one sorry.

[eight0]

Not sure if you have come across this, but it's the best info on Dual disc conversion I have round.

http://blacksquaremotorcycle.com/dual-disc-conversion/

If you have the Asymmetrical hub:

'the right side fork slider has a caliper bracket mounting point/post, which is offset by exactly 3 mm when compared to the left.  What this means is that the caliper will sit 3 mm closer to the rim, tire and spokes and will, therefore, line up with the rotor perfectly'

'There is a gap between the slider and the top caliper bracket!  It is exactly 3 mm.  That’s an easy one to fix.  If you are re-using the original front fender, its mounting bracket will fill some of that 3 mm gap, the rest can be taken up by standard  6 mm washers (one at each mounting point).   If you are not using a front fender at all, then just put two 3 mm thick washers to fill the gap when installing the calipers.'

copied and pasted from the Blacksquare site.

[Erny]

This is very good reference & detailed description, thanks for sharing it!

Wondering what hub type I'll find on my 550K1.

Additionally, is there some source (ideally EU) to obtain modified or machined speedo gearbox retainer that is ready to go? I'd like to keep original parts untouched in box, don't want to modify.

[Bryanj]

The drive is easy to modify and same as 750 so should be lots of used ones out there. It used to be that the hub with flats was more common than the round one.

[Erny]

OK, so I'll first look what hub I have and start looking to buy some drive for modification on ebay

[cb550k-aaron]

I'm hopefully going to get round to fitting all this tomorrow, I will post my findings!

[cb550k-aaron]

So, my Fork legs, the Right side one the posts are 3mm closer to the wheel, as is my disc on the hub so I needed absolutely no modifications to mine at all. Everything lines up as it should etc. The only thing I had to do was modify the Speedo retainer by milling off the lugs so it fit snugly inside the actual disc inner. I'll post pictures soon

[Bryanj]

Its NOT the retainer to modify its the drive plate and just milling it to fit inside wont work as there is nothing to make it turn with the hub, on the hub with flats two ears are bent down to engage on the flats. If you used countersunk screws you may be able to drill and tap the hub to hold the drive plate on.