Topic: CB750K dual front brake conversion clarification

[Dolomite]

Good morning all, I have begun my procurement of parts to change my single disc setup to a dual, I just needed some clarification on the speedometer drive. Is it the CB500/550 drive plate or the entire assembly that is used without modification?

[bryanj]

Neither its a myth, you need to reasurch more to get the proper info. I have put it on here many times. You need the VERY early cb 750 drive plate and still have to make small mods.

[Dolomite]

Thanks. Do you have the link to your post handy? If not I'll look for it later.

[bryanj]

Sorry cant figure out how to do links on dumbfone but look for 500/550 twin disc as most of it is the same.

EDIT

Go to manuals and technical,
Click on menu at top right
Click on 500
Scroll down to twin disc and download. In it is a picture of an original Honda part drive plate.

[Dolomite]

Attached two photos, which one is the one needed, the retainer or the cover?

[Dolomite]

Or I just found this on ebay. I am assuming its just a ready made version of what I need to modify?

[PeWe]

I used that one on my dual brake build. I found later another version at Yamiya that I bought just for sure, no need to drill 2 holes in hub and make thread for the screws holding it that must be centered.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_184_87&products_id=373

Note the chrome cover will not be used for dual disc.

[Bankerdanny]

You need the box (lower picture) not the retaining ring. Then you cut off the rim so it is flat like in the eBay version (I used a cutoff wheel on my angle grinder) so that it sits flat on the hub. Then I drilled two 3/32 holes and used roll pins to make sure then plate won't rotate.

[Dolomite]

I used that one on my dual brake build. I found later another version at Yamiya that I bought just for sure, no need to drill 2 holes in hub and make thread for the screws holding it that must be centered.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_184_87&products_id=373

Note the chrome cover will not be used for dual disc.

What secures the flat sides to the hub?

[Dolomite]

You need the box (lower picture) not the retaining ring. Then you cut off the rim so it is flat like in the eBay version (I used a cutoff wheel on my angle grinder) so that it sits flat on the hub. Then I drilled two 3/32 holes and used roll pins to make sure then plate won't rotate.

So do i even need to buy a new retainer or is it the same as just cutting the lip off mine? I'm assuming this is because otherwise the speedo gear interferes with the caliper? I don't have the bike in front of me, it's still at the mechanics.

[Bankerdanny]

Don't pay attention to the exact names on those pictures. The chrome ring is the retainer, it holds the box onto the hub and keeps it from spinning.

With the right side disk in place you can't use the retainer ring.

You should be able to modify your existing box just like I did mine from the photo. You cut off the vertical edge so that the box sits flush against the hub in the middle of the rotor as in pictures 2 and 3 in my post.

[Dolomite]

Okay, that's what I thought. Thanks for the help everyone!

[bryanj]

There is apicture if you follow the directions i gave that shows where to bend so its driven by the flats on the hub

[Dolomite]

There is apicture if you follow the directions i gave that shows where to bend so its driven by the flats on the hub

I went to where you said but the document is only one page and just says "Fit replacement Speedo drive plate. (This may necessitate cutting part of the aluminium disc center out to form two rectangular slots)." The directions just all seem very vague. Is there parts of the document missing?

[Bankerdanny]

You need to carve pockets on the back side of the rotor center to go over the tabs on the box. You will still need to make other mods so the box fits through the center of the rotor.

[bryanj]

you do not need to modify the back of the rotor in any way if you alter the drive the way I said. when I go to the file there are 2 pages with a picture on the first. as I am in UK and not a "techie" I do not know why you cant see it. If you PM me your email I will send you the original word document but don't forget there is a time difference and I work lots of hours

[Bankerdanny]

you do not need to modify the back of the rotor in any way if you alter the drive the way I said. when I go to the file there are 2 pages with a picture on the first. as I am in UK and not a "techie" I do not know why you cant see it. If you PM me your email I will send you the original word document but don't forget there is a time difference and I work lots of hours

The modified box from my photos also does not require any mods to the rotor.

[PeWe]

I used that one on my dual brake build. I found later another version at Yamiya that I bought just for sure, no need to drill 2 holes in hub and make thread for the screws holding it that must be centered.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_184_87&products_id=373

Note the chrome cover will not be used for dual disc.

What secures the flat sides to the hub?

This should to fit the hub, no holes to drill. Look at the hub and you'll see it has flat sides the Yamiya version grip.

Edit: Which front wheel do you have? Later hub like K7 look different than K1-K6. K0 differs from the later as I have read somewhere, wider hub.

[Dolomite]

It's a K8 hub, without having it in front of me its difficult to say what style hub. Should be back from the mechanic this week.

[PeWe]

OK, the Yamiya version will most likely not fit then....