Topic: Dual disc for modified '78 750F

[turborat]

New to forum.  Need a little assistance with front forks/brakes if possible.  Done my best to search for this information.

I have been working on a cafe style '78 CB750F for a few years off an on.  As you know the '78F had forged wheels and dual disc up front.  I went to laced wheels front and back.  As a result I lost the dual disc configuration because the right hand disc touches the fork.  Finding notes on how to perform the dual disc I procured the parts with the same result.  As I look at the '78 5-bolt discs, they have less offset than the earlier 6-bolt disc..  My questions is this.  Is there a different in the distance between the tubes on the '78 F front end vs. other 750 models.  If not, then can I assume that fork bottoms from an earlier model are spaced differently and will solve the problem and allow for the dual disc conversion as described using 55o speedometer parts.

Thanks
 

 

[flybox1]

big changes between K and later F brakes/wheels
you might need to go to an all K component (lowers) front to get it to work with wire rims. 
i dunno.  hopefully someone here can chime in.
i used 78K forks(would be a direct fit on your F trees), and '71K 6-bolt rotor, 71K calipers. Early K rotors.
aside from shims on the caliper mounts for alignment(washers), reduction of bolt head height(dremel), and a 15 min mod of the 750K1 speedo drive plate(dremel), it was a plug and play.
no 550 speedo drive needed 

[turborat]

OK, So I think you have confirmed one of my questions.....the tube spacing (triple tree) is the same between K and later F.  Sounds like I need K lowers along with K calipers and mounts along with a little massaging to get a fit.  Correct?  Double check me here.

Any changes in 6 bolt discs year over year?

[flybox1]

yeah, that sounds right. check my conversion on pg 3..
http://forums.sohc4.net/index.php?topic=105018.msg1341362#msg1341362

and the 6-bolt discs are the same, however i went with these....
http://www.vinmoto.org/gallery/v/VinMoto-Garage/album03/Godfferys-Garage-123/album185/Brake+Rotors+_+Thinned+and+Drilled/HONDA+Front+brake+rotors+CB750+K+-+F/

he also has calipers for sale.

[HonderCB]

a lot of guys who want to make the spoke wheel conversion on the 77 and 78 F models swap front ends for goldwing front ends.  They had wire wheels and dual front discs.  Much less headache, plus it is a bit of an upgrade on the suspension as well.  I'm pretty sure Tweakin and BrandEn have done it on their bikes, both are members here.

just throwin it out there for ya.  Welcome to the forum, the more "F-ers" the better!

[turborat]

Thanks Honder.  I appreciate any advice.  This is my first build and I am certainly doing it the hard way.  Someday it will be on the road.  Too many projects and this one is last in line for any cash. 

I recall when I first rode the bike a few years back and how horribly it stopped.  Call ahead and reserve a spot bad.  Going with bradied lines an updated MC.  Thinking I need to upgrade to modern brake disc stainless steel.  Not aware of anything but new EBC.  Any other options than can be used on the K front end?  Cheap Cheap.

[andrewk]

Check this thread out- some nice machine work here- big brakes on a stock F front end.   http://forums.sohc4.net/index.php?topic=117145.msg1324284#msg1324284