Topic: CB750 Dual Disc Conversion - Speedo Drive Mod and Bolts

[SKTP]

phewwww....you scared me...I am goign to go mock it up with the 'too thick bolt heads (the are goign to be lathed down)...

[SKTP]

Just pulled the axel out and put it in the new wheel with all the fixin's...it all fit perfectly, even with the stock bolt heads...If my buddy with a lift calls me back, its GAME ON (and wheel on)  

EDIT: Crap...the clearence is so tight with the bolt heads....I have deceided to have 1mm taken off them

[SKTP]

Success...!!!

Its now ready for dual disk/dual calipers...now if only my bank account was...I'll be rockin' the 'style right side rotor' for a month or 2...

(also that oil leak is not from the bike)

[JLeather]

Hopefully this isn't a hijack, but has anyone on here run dual-disc spoked K wheels on a 77/78 F frontend?  I'm looking to do this in the near future to my current build.  I've been taking some measurements and it seems fairly straightforward if I'm not missing something.  The F-model rotors are smaller than the K's by about 5/8" or so, so I figure I can chuck the K-rotors in a lathe and turn them down to the same OD as the F-model ones.  I need to do this because I haven't found a 6-bolt Honda rotor with the same OD as the CB750 F's.  After that the other major difference appears to be that the F-model rotors are spaced a bit wider than the K'd, roughly 1/4" or so.  I figure I can make two sets of spacers to go in between the fork and the caliper mount to space the F-calipers inwards 1/8" on each side and end up with the correct spacing.

Am I missing something here?  Has someone tried this and succeeded or failed or figured out something else before me?

[Gamma]

Can't help you with your main question JLeather.  But before you start spacing the calipers away from the forks, you might be able to space the discs closer to the forks instead. (Further from the wheel hub.
On the 76 F1, I have made one 2mm spacer to sandwich between the extra disc and the hub. This puts the additional disc pretty much in the same position as the original disc, in relation to the centre of the hub.  I can do this because I am not going to run a cable speedo, but will use a bicycle one. 
http://i192.photobucket.com/albums/z293/galaxy8155/spacer.jpg[/img]]

And for the information to others on this forum. Doing this and putting the discs at the same distance from the fork legs (4.15mm approx) meant I only had to file 2.5mm approx from the lower caliper mount and add no washers to the top two bolts.
Mind you, you've got to do it slowly, I nearly filed too much.
Also had to take a little bit off the fork leg web near the lower caliper mount.
Just got to turn a spacer to fill the redundant speedo drive area.
http://i192.photobucket.com/albums/z293/galaxy8155/DSC02499.jpg[/img]]
http://i192.photobucket.com/albums/z293/galaxy8155/DSC02498.jpg[/img]]

[flybox1]

ZOMBIE THREAD ALERT!! 
this thread is probably visited quite often by those converting to dual front disks.  good info here. 
just wanted to add a nuts and bolts parts list for the conversion. then let this thread die, again.

I ordered all new zinc hardware for my two front 750 K1 calipers, caliper arms, and dual disc front hub @ Bolt Depot $13 + $11 shipping.
Nice to get all from one place.
here's the parts list for others (for 2 calipers) hopefully it will be of use to someone sourcing hardware
quantity, BoltDepot's part #'s, specs, use....

6, #10687 - Metric flange nuts serrated, Zinc plated class 8.8 steel, 8mm x 1.25mm Front Hub Rotor mount flange nuts
10, #4527 - Metric flat washers, Zinc plated steel, 6mm (calpier arm shim washers/B pad adjuster washers)   
4, #4529 - Metric flat washers, Zinc plated steel, 8mm (calpier arm shim washers)         
2, #6223 - Metric hex bolts, Zinc plated class 8.8 steel, 8mm x 1.25mm x 35mm lower caliper arm mount bolt
6, #6235 - Metric hex bolts, Zinc plated class 8.8 steel, 8mm x 1.25mm x 110mm Front Hub Rotor mount bolts, heads need to be milled to clear the speedo drive
4, #6064 - Metric tap bolts, Zinc plated class 8.8 steel, 6mm x 1.0mm x 30mm    upper caliper arm mount bolt
2, #5143 - Metric machine screws, Phillips flat head, Stainless steel 18-8, 6mm x 1.0mm x 50mm   B pad adjuster bolt
2, #13572 - Metric hex jam nuts, Stainless steel 18-8, 6mm x 1.0mm    B-pad adjuster nut   
4, #15754 - Metric socket cap, Class 12.9 steel black oil finish, 10mm x 1.25mm x 50mm CB750 K1, Caliper Hex bolt - i'll cut these down to 45mm  verify this is the right bolt for your calipers before ordering

[antman180]

Thanks Rob, Bolt list was great, just sent off my order this morning
Cheers
Anthony

[Mcwilliams570]

Digging this post up again. I am starting to gather parts for my next project and was test fitting stuff and ran into this problem.



the lower bolt I think was suppose to be 8mmx35mm I hand tightened it and it seems like its going to start stripping if start cranking down on it with a tool. You can see how much is sticking up still. I tried this bolt and several other bolts on a different fork and same results. Is this not the bolt I am suppose to use? Well crap just looking over this before I post and I see this is a cb750 dual disc conversion I am doing a 550 conversion anyone know if that lower bolt would be the same for a 550/750

Thanks Matt

[flybox1]

are you sure that the bolt you are using is M8(1.25tp)?
as in my parts list above, M8x35mm(1.25) is the correct bolt for the 750 fork lowers.
check the 550 parts fiche...

[Mcwilliams570]

Just checked it that is the bolt I am using when I get home will check to see if the 550 is the same thanks for responding so quick.  Matt

[Mcwilliams570]

Got didn't clean the hole out good enough some crap in there still goes in the way it should now thanks

[Wobbly]

For those of you who like it less complicated, this is what I bought on Ebay:
http://www.ebay.de/itm/Honda-CB-750-Four-K6-K7-F1-F2-Screw-Bolt-Nut-washer-Drive-Kit-Double-second-Disc-/360623679453?pt=DE_Motorradteile&hash=item53f6d8a7dd

[flybox1]

^PERFECT KIT.
someone else here on the board also offers that speedo drive plate, too.

[Mcwilliams570]

Any idea who the member is that is the next project was just going to cut it with a dremal.  Matt

[flybox1]

cant find it.
the speedo drive plate mod is easy with a dremel, etc.
godffery also can mill the back side of the rotor carrier to fit an unmodified drive plate.

[Gman]

All,
Member scottly also does the milling of the rotor and milling the drive plate for a dual disc conversion.  I have a 550 and had him drill my rotors and mill the pockets/drive plate while he was at it.  He was good to deal with and did a great job w/the dirlling and milling.  You can find him in the services offered section.

Cheers,
G

[Tuche]

Perfect! I will do this in my CB500 '73. Looking to this pictures, It's the same pieces I have on my 500!

[derek.kraese]

Did anyone have issues with how close the speedometer cable is to the rotor on the right side?

Sent from my SM-G960U using Tapatalk

[MCRider]

Did anyone have issues with how close the speedometer cable is to the rotor on the right side?

Sent from my SM-G960U using Tapatalk

"inch is as good as a mile"   

If you don't have a front fender, could be an issue. With a steel fender, you can ziptie it to maintain the tiny clearance.