Author Topic: CB750 Dual Disc Conversion - Speedo Drive Mod and Bolts (Read 42535 times)

SKTP · « **Reply #25 on:** July 20, 2009, 08:20:44 AM »

If I follow correctly, you are sayign there is enought rom for the "Speedo cover ring" and the "Drive plate" if you modify both parts (cut the ring as flat as possible and bent the tangs out and make sor of a flatish drive plate)?

if this is the case this sound far easier than attempting to dremel a brake rotor....thanks

MCRider · « **Reply #26 on:** July 20, 2009, 08:30:11 AM »

Quote from: SKTP on July 20, 2009, 08:20:44 AM

If I follow correctly, you are sayign there is enought rom for the "Speedo cover ring" and the "Drive plate" if you modify both parts (cut the ring as flat as possible and bent the tangs out and make sor of a flatish drive plate)?

if this is the case this sound far easier than attempting to dremel a brake rotor....thanks

Is this directed at me? If so...

My experience is with K-1 and K-2, so hopefully it is relevant. Some parts changed over the years. The chrome trim ring (speedo cover ring?) is discarded. Otherwise your description sounds right. I ground my drive plate down on a bench grinder holding it with vice grips. I left enough of the diameter in 2 places to bend over as tabs. Very crude but worked fine.

I have since had one made where the machinist milled off the flange and the diameter to fit down inside the disc, then welded 2 small tabs. There are pictures of mine in the threads somewhere. Common topic.

Oh, I see someone has copied it into your thread about 14-15 posts back.

SKTP · « **Reply #27 on:** July 20, 2009, 08:34:01 AM »

Sorry MCrider...that was directed at fishhead but thanks regardless...at this point, I think I am just goign to find a machinist and have him mill my rotor liek in the big pic afew posts up

MCRider · « **Reply #28 on:** July 20, 2009, 08:36:37 AM »

Quote from: SKTP on July 20, 2009, 08:34:01 AM

Sorry MCrider...that was directed at fishhead but thanks regardless...at this point, I think I am just goign to find a machinist and have him mill my rotor liek in the big pic afew posts up

No problem, machining is always good. Good luck!

754 · « **Reply #29 on:** July 20, 2009, 09:23:27 AM »

Even easier way;
drill 2 holes into hub or wheel, 17/64ths.. about 1/4 in deep.

drill 2 holes in the drive plate , 1/4 in diameter, weld in 2 pins so they stick out 3/16inch, then grind flush on outer side.

NOTE, if you drill drive plate first, then use as a guide to drill the hub, you should be bang on.

fishhead · « **Reply #30 on:** July 20, 2009, 09:30:25 AM »

Quote from: SKTP on July 20, 2009, 08:20:44 AM

If I follow correctly, you are sayign there is enought rom for the "Speedo cover ring" and the "Drive plate" if you modify both parts (cut the ring as flat as possible and bent the tangs out and make sor of a flatish drive plate)?

if this is the case this sound far easier than attempting to dremel a brake rotor....thanks

Yes.

On the single disc chrome speedo drive cover thing (after sandcast) , it needs to be cut down like the pic in the post above shows so it wont interfere with the speedo drive.

You may need to tweek the tangs up past the discs to get clearance (I dont remember if they were absolutely flat or slightly tweeked up to clear the 2nd disc- I dont remember if the disc and hub protrusion are the same height-You'll see what needs to be done when you put the 2nd disc on).

EDIT:
The 75-77 GL 1000 disc mounting bolts are what you want for the dual disc. They are pictured with the speedo drives and are longer (for the 2nd disc) and the head of the bolts are shorter (to clear the speedo drive).

SKTP · « **Reply #31 on:** July 20, 2009, 11:17:12 AM »

75-77 GL 1000 disc mounting bolts the hunt starts now!

Thanks everyone....

SKTP · « **Reply #32 on:** July 21, 2009, 05:12:15 PM »

parts 18 and 20 from the looks of it...

SKTP · « **Reply #33 on:** July 29, 2009, 03:59:59 PM »

Any leads on 77 GL 1000 Front disk mounting bold greatly appreciated

JohnG · « **Reply #34 on:** July 29, 2009, 05:10:23 PM »

Hi
I have a '76 750F and would like to add a second front disk. Specifically I would like to add a second stock disk and another stock caliper. This leaves me to ask:

* does someone make a mirror image caliper bracket of mine? (I have a notion that the caliper and bracket for the first F series was different from the earlier K's)

* is it any more work if I want to mount the calipers behind the fork legs?

* does the stock master cylinder need to be replaced because the travel becomes too great when moving two pistons?

Aside: many years ago I was looking at Ebay and saw for auction a yellow CB750F (which I think makes it a '76) which had low mileage, all stock parts, and what appeared to be a factory dual disk setup in front. The calipers were greyish. Maybe European. Anyone know anything about the existence of such bikes?

Since we are on brakes - is there any commonly used shop that drills rotors???

thanks!
john

bikebitzofvt · « **Reply #35 on:** July 29, 2009, 09:28:31 PM »

Quote from: JohnG on July 29, 2009, 05:10:23 PM

Hi
I have a '76 750F and would like to add a second front disk. Specifically I would like to add a second stock disk and another stock caliper. This leaves me to ask:

* does someone make a mirror image caliper bracket of mine? (I have a notion that the caliper and bracket for the first F series was different from the earlier K's) Yes, Honda made it. It's the same bracket and caliper as the left side, checked and the part numer is the same for your bike as the caliper bracket from a 77 750K, among others

* is it any more work if I want to mount the calipers behind the fork legs?Switch the legs from left to right, there's some useful info in this thread:http://forums.sohc4.net/index.php?topic=54716.0

* does the stock master cylinder need to be replaced because the travel becomes too great when moving two pistons?Yes, GL1000 is a common donor as it maintains the period look, any master from a dual disc bike will work in theory

Aside: many years ago I was looking at Ebay and saw for auction a yellow CB750F (which I think makes it a '76) which had low mileage, all stock parts, and what appeared to be a factory dual disk setup in front. The calipers were greyish. Maybe European. Anyone know anything about the existence of such bikes?Dual front disc has been a popular mod since the 70's

Since we are on brakes - is there any commonly used shop that drills rotors???Anubis cycle has a special going for SOHC'ers, the post was a few days ago, here's the link:http://forums.sohc4.net/index.php?topic=55462.msg599474#msg599474

The only other thing to note is the GL1000 rotor bolts have been discontinued. I've started a search for replacements as I've two bikes in my shop (a 74 550K and a 77 750K) that I've amassed all the other needed components for the dual disc conversion...
Good luck!

MCRider · « **Reply #36 on:** July 29, 2009, 09:44:35 PM »

Was there anything special about the GL bolts? Did they have thin heads to clear the speedo drive or some such? Otherwise...

I've got like 3 or 4 sets of 110mm long bolts I've accumulated, but I'm thinking they will need machine work to fit nicely.

fishhead · « **Reply #37 on:** July 30, 2009, 04:04:13 AM »

The head of the GL disc bolts are thinner to clear the speedo drive and longer for the addition of the dual disc

Top: GL bolt
Center: Store bought bolt
Bottom: CB bolt

The CB and GL bolts have a thicker shaft than the store bought bolts and fit the holes in the disc and hubs better (Less slop than the store bought bolts).

I have found some Allen head bolts the same size as the GL bolts, but they would need to be put in from the left side (backwards- as the Allen head is tall) and thinner nuts would need to be used ( I haven't researched the thinner nuts, yet).

I don't have any stock discs to measure how much of the bolt would protrude out past the 2nd disc (and possibly hit the speedo drive- with the Allen bolts in backwards) and it is why I havent pursued it.

Any one care to take a measurement?

MCRider · « **Reply #38 on:** July 30, 2009, 04:58:11 AM »

Quote from: fishhead on July 30, 2009, 04:04:13 AM

The head of the GL disc bolts are thinner to clear the speedo drive and longer for the addition of the dual disc

Top: GL bolt
Center: Store bought bolt
Bottom: CB bolt

The CB and GL bolts have a thicker shaft than the store bought bolts and fit the holes in the disc and hubs better (Less slop than the store bought bolts).

I have found some Allen head bolts the same size as the GL bolts, but they would need to be put in from the left side (backwards- as the Allen head is tall) and thinner nuts would need to be used ( I haven't researched the thinner nuts, yet).

I don't have any stock discs to measure how much of the bolt would protrude out past the 2nd disc (and possibly hit the speedo drive- with the Allen bolts in backwards) and it is why I havent pursued it.

Any one care to take a measurement?

I was thinking it was something like that, its been a long time since I've looked at my set up, which is in a million pieces. In one of my parts bags, I have 6 nuts that were ground down thinner, I thhought they were from my duallie set up and so they are.

I may have take the bolts I've collected to a machine shop and have the heads turned this time.

As you say the shafts may not be the best of fits, but shouldn't be a real problem.

JohnG · « **Reply #39 on:** July 30, 2009, 12:27:15 PM »

Earlier I wrote:

Aside: many years ago I was looking at Ebay and saw for auction a yellow CB750F (which I think makes it a '76) which had low mileage, all stock parts, and what appeared to be a factory dual disk setup in front. The calipers were greyish. Maybe European. Anyone know anything about the existence of such bikes?

which was poorly worded. The bike was claimed to be factory original which made me wonder if in Europe or someplace Honda provided dual disks for the Fs, which would then mean a potential source of parts. I'm gonna guess the answer is an emphatic NO...

On master cylinders, has anyone ever bored out theres so the bore was about twice the area as for a single disk? (which would not mean twice as big as area goes as the square of radius). This would save the hunt for an MC; you could get it bored and then buy a rebuild kit. However... there might not be nearly enough meat there to bore and this may all be a moot point.

fishhead · « **Reply #40 on:** July 30, 2009, 01:24:39 PM »

Quote from: JohnG on July 30, 2009, 12:27:15 PM

Earlier I wrote:

Aside: many years ago I was looking at Ebay and saw for auction a yellow CB750F (which I think makes it a '76) which had low mileage, all stock parts, and what appeared to be a factory dual disk setup in front. The calipers were greyish. Maybe European. Anyone know anything about the existence of such bikes?

which was poorly worded. The bike was claimed to be factory original which made me wonder if in Europe or someplace Honda provided dual disks for the Fs, which would then mean a potential source of parts. I'm gonna guess the answer is an emphatic NO...

On master cylinders, has anyone ever bored out theres so the bore was about twice the area as for a single disk? (which would not mean twice as big as area goes as the square of radius). This would save the hunt for an MC; you could get it bored and then buy a rebuild kit. However... there might not be nearly enough meat there to bore and this may all be a moot point.

The 76 F had the spoked wheel and the old style antique swinging caliper arrangement (like the K). I am not aware of any "Factory" original dual disc 76 F's or K's. Honda did at one time list the R/S caliper/bracket for the racing models (970 product code) but they were expensive and hard to find back then and harder still to find now. The L/S caliper is easily modified to fit the R/S.

The 77 F did come with dual disc, but the wheel was changed to the Comstar and the calipers were mounted behind the forks (conventional style- with 2 bolts- not the swinging caliper style like on the earlier bikes). The discs were also changed to a 1 peice 5 bolt disc (from the earlier 6 bolt 2 peice disc).

Instead of boring out the stock 1/2 inch master cylinder it would probably be easier to get a 5/8 master cylinder off another bike. Alot of people use the GL 1000 master cylinder (11/16) but the 5/8 works better,JMO.
I tried to bore one out once, but I ruined the master cylinder. You would need to bore out the piston bore and then bore out the recess where the circlip sits to hold the piston and stuff inside the master.
Maybe some one else has had luck with boring the master cylinder ?

SKTP · « **Reply #41 on:** July 31, 2009, 10:21:36 AM »

Still searching for 77 GL1000 bolts...but the wheels are almost ready to go

SKTP · « **Reply #42 on:** August 07, 2009, 01:06:35 PM »

http://www.youtube.com/watch?v=BolGUBlhLrs

I am planning on sending my rotors out to Anubis Cycle http://www.anubiscycle.com/documents/request.jpg

Nobody I have talked to locally wants to touch rotors at all...

I just watched the video above and saw there's a $5 discount for SOHCers...I searched the forum for the SOHC Anubis form but came up empty...anybody know where that link is? Thanks

MoTo-BunnY · « **Reply #43 on:** August 07, 2009, 03:11:39 PM »

I have used a 14mm master cylinder that works for either single or dual disks, for over 3 years and many miles - works great.

(the below is a copy/paste from old posts I have made a few times now)

http://forums.sohc4.net/index.php?topic=28649.msg294679#msg294679 (see this thread)

I replaced my old stock master cylinder with one of these eBay units - just like the one starting this thread. It was one of the single best improvements I have done yet - BIG improvement in braking.

(full chrome version)

If you want to upgrade your master cylinder to one that will support one OR two discs (and REALLY improve your braking), you can get this style off of feeBay:

This is apparently a very close copy (and a very good one, at that) of the Nissin master cylinder? (it could even be made by them but there isn't any manufacturer markings anywhere on either of the ones I bought) This company sells them and I have bought and installed two of them on two different bikes ('73 CB500 & '79 CB750K) with fantastic results: The style I used were 14mm piston - works great for our Hondas - the stock brake hose and mirror even fits the threads - and the brake switch hooks right up if you extend the wires and change the wiring connectors)

usa-motorcycles-inc

However, they seem to be running fewer of these at auction than they used to and are jacking up the price. (I bought both of mine at $39.95 each - now the same style is $49.95+) There is also a full chrome version for $79+

You don't have to be particular with what brands they post in the title as long as its the 14mm piston model and it looks like this picture. . .they are all the same. I have noticed bidding wars over $80.00 on one that says "VTX" or Shadow or something while the exact same part in a different auction goes for beginning bid ($49.99) . . . . lol.

SKTP · « **Reply #44 on:** August 10, 2009, 03:32:56 PM »

Since I have drag bars...and it s tight fit on there for the Front master...I was think this one was the way to go...

Anybody used this type? Any info appreciated

SKTP · « **Reply #45 on:** August 28, 2009, 06:22:26 PM »

So here's where I am at....very close

I could not get my hands on GL1000 hardware...these bolt are the strongest steel I could find and are the right length. I plan on bench-grinding the heads down and then I think its all good...if you look at that picture (A) the clearances are very tight the end of the cylendar is lower than the outermost portion of the disk...I think that's ok due to the speed-O cable being so thin and inset (see below)

My friend works as a concept car fabricator so we have deceided to use industrial adheasive to mount the speed-O drive ring to the hub...this is how it sits for mock-up...is this how yours looked? Will spacers or some sort be required or is the hub and the speed-O with out the speed-O collar the perfect width? Judgign from this http://www.salocal.com/sohc/tech/dual_disks/dual_disks.htm it seems that is the case...Hopefully I will have everything on the wheel and on the biek tomorrow...I plan on just rocking 2 disks until funds allow for a new master cylendar, stainless brake lines, etc...

fishhead · « **Reply #46 on:** August 29, 2009, 06:55:54 AM »

Quote from: SKTP on August 28, 2009, 06:22:26 PM

My friend works as a concept car fabricator so we have deceided to use industrial adheasive to mount the speed-O drive ring to the hub...this is how it sits for mock-up...is this how yours looked? Will spacers or some sort be required or is the hub and the speed-O with out the speed-O collar the perfect width?

Not really sure I understand the question completely, but, the drive plate (glued to your hub) is free floating and doesnt add any width to the axle length. With or with out the speedo drive plate, it wont affect the width of the speedo drive mechanism(gearbox) or total axle length.
Can you measure the height of the modified disc bolt heads?
Fishhead

SKTP · « **Reply #47 on:** August 29, 2009, 05:58:59 PM »

I was more meaning...if the front wheel is free floating on the axel...now, after modification, if it is now more narrow, or more wide...will that move the fork legs in or out at the axel? what determines the width betwwen the bottom of the fork legs? if there's too much play will the wheel move side-to-side on the axel between the legs?

SKTP · « **Reply #48 on:** August 30, 2009, 07:22:05 AM »

Quote from: fishhead on August 30, 2009, 07:17:29 AM

but you will stilll need to get the GL axle and axle spacer.

Are you sure? This http://www.salocal.com/sohc/tech/dual_disks/dual_disks.htm makes no mention of that at all ever...I know the 550 drive thing is wrong in it...but it seems to have been used for numerous dual disk conversions and nobody has ever mentioned the GL1000 axel and axel spacer

fishhead · « **Reply #49 on:** August 30, 2009, 07:40:35 AM »

EDIT=I have removed my previous statment as if was for fitting the GL front end and not the CB front end.

Crap, You are right, I am wrong. I just assumed you had a GL front end. The CB parts will work fine ( and is what you need ) for the CB Front forks.

DOH!!

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Author Topic: CB750 Dual Disc Conversion - Speedo Drive Mod and Bolts (Read 42535 times)