Author Topic: Twin Piston Brake Upgrade Using OEM parts For CB750F  (Read 38766 times)

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Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #125 on: May 25, 2017, 11:28:32 pm »
OK. The calipers can be spaced inward by about 1/8" each side to line up with the K rotors and hub. If the F2/3 rotors were narrower than the K, it wouldn't work, since the calipers bolt against the inside of the fork leg, and can't be moved outwards.
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Offline seanbarney41

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #126 on: May 25, 2017, 11:34:40 pm »
don't forget about spoke clearance...no idea if this will be an issue or not
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Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #127 on: May 25, 2017, 11:43:13 pm »
Spoke clearance isn't an issue with the spoke wheel or the Morris; I've already checked for worst case. ;D
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Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #128 on: September 19, 2017, 07:52:21 pm »
A spoke front wheel will bolt directly to the F2/3 forks. Keep the axle assembly the same as with K forks: the head of the axle on the right side, then the K speedo drive (or equivalent spacer). On the left side, use the K spacer, and the axle nut. This will center the wheel in the forks.
The spoke wheel has the brake rotor inboard of the F rotor, so spacers approximately .130" thick need to be fitted between the bracket and the lugs on the fork leg to center the bracket over the rotor. To add a rotor on the right side, the spacers need to be thicker, like about .245", since the K hub isn't symmetrical. All other issues with dual disks on a K fork, like the speedo drive, are handled the same way.   
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Offline RAF122S

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #130 on: October 03, 2017, 07:14:39 am »
Yes, that is a good deal indeed.  I wish I had dual disc on cx500, requires fork leg swap and some GL500I parts...or from one.

Having them Teflon coating gives a very close finish to original texture and sheen. A fellow on CX/GL forums has been using that method on his rebuilds and restorations.  It is impervious to brake fluid and very easy to clean. :D

David- back in the desert SW!

Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #131 on: January 19, 2020, 07:21:07 pm »
The twin piston pads are available in different compounds: EBC brand FA 69 pads, which are what my local dealer stocks, have a friction coefficient rating of GG, while the EBC FA 69 HH pads have the grippier HH rating..
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Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #132 on: February 13, 2020, 06:48:24 pm »
I've just found out that there were two different versions of the brackets with the 65mm center-to-center fork lug spacing. I don't know which bikes these came from, but the difference is visually apparent. The one on top mounts the caliper higher and further back than the lower one. I believe the one on top is correct, but all of jaguar's pics on the first post have been eaten by photo-phukit. >:(
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Offline jaguar

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #133 on: February 17, 2020, 03:35:17 am »
Top looks correct to me

Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #134 on: February 17, 2020, 09:06:58 pm »
Thanks!!! ;D
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Offline steve_K8_CB750

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #135 on: July 14, 2020, 07:19:41 pm »
Hi, thanks for this info it’s really helpful. I’ve picked up a set of CB900F 1981 front calipers, they fit perfectly. I’m having one problem though and I’m wondering if anyone here has had the same problem. I’ve ordered Honda seals and have cleaned and rebuilt the calipers. The seals however are a nightmare. I keep ripping them while trying to insert the pistons. It’s almost as if the seals are the wrong size. I’ve gotten the parts numbers from Hondapartshouse.com

45109-166-006
45209-166-006

Any help or advice would be greatly appreciated. Thanks

Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #136 on: July 14, 2020, 08:31:10 pm »
Steve, the two piston calipers come with different diameter pistons, and if your seals seem to be the wrong size, they probably are the wrong size. The part numbers even from Honda are not always correct: the factory manual for my FT500 says the rear caliper has 30mm pistons, but they are actually 27mm. Are the seals too big or too small? What is the diameter of your pistons?
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Offline steve_K8_CB750

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #137 on: July 15, 2020, 04:36:44 am »
Thanks for the reply. The diameter of my pistons are 32mm.
The seal fits in, however, it seems ever so slightly a smaller diameter than the caliper, in that, when you push the seal to one side on the caliper (while the seal is in place), the far edge of the seal nudges out “proud” of the caliper wall.

Offline NHgranite

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #138 on: July 15, 2020, 05:44:22 am »
Paging Jaguar; is there any chance you can try reposting the images from your original post? 

Thank you in advance.
1973 CB500/4

Offline RAF122S

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #139 on: July 15, 2020, 09:47:48 am »
If he can, then upload directly to the forum ensures longevity of the photos.
David- back in the desert SW!

Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #140 on: July 15, 2020, 07:11:54 pm »
Thanks for the reply. The diameter of my pistons are 32mm.
The seal fits in, however, it seems ever so slightly a smaller diameter than the caliper, in that, when you push the seal to one side on the caliper (while the seal is in place), the far edge of the seal nudges out “proud” of the caliper wall.
The CB900 came with 30mm calipers, and use the same 45209-166-006 piston seal as my Ascot front caliper. You want the seals for a V65 Magna 32 mm caliper.
Parts numbers should be: (don't sue me if I'm wrong ;))
piston seal 45209-MA7-006
dust seal 45109-MA7-006
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Offline steve_K8_CB750

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #141 on: July 16, 2020, 05:33:01 am »
Scottly, you're a life saver, I was really stumped with this, and never thought to check the piston size in case the calipers weren't original. Thanks very much for your help and safe riding.

Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #142 on: July 16, 2020, 09:05:36 pm »
Before I forget, in order to bleed the two piston calipers, the bleeder needs to be at a 45-50 degree angle rearward, instead of straight up and down like most calipers. The hole where the bleeder passage enters the piston bore needs to be at the top. On some applications, the mounts will not position the bleed passage at the top, resulting in a mushy feel at the lever. In this case, reposition the caliper and fit a thick shim between the pads while bleeding.
 
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Offline jaguar

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #143 on: July 18, 2020, 04:27:13 am »
I think most of the pictures are lost to photobucket.
Will dig around though


Offline steve_K8_CB750

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #145 on: October 16, 2020, 04:45:28 pm »
Thanks again to everyone for your help. It's taken an age to catch up editing the video to where I am now in the build, but I wanted to just say thanks for all your help and to share the link to the video incase anyone is interested. I would be still trying to get those seals in place if it wasn't for you guys. I gave you a shout out in the video. Safe riding and happy building


Offline scottly

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Re: Twin Piston Brake Upgrade Using OEM parts For CB750F
« Reply #146 on: October 16, 2020, 09:55:14 pm »
Steve, if you still have questions about the MC piston diameter for your dual 32mm two piston calipers, I would suggest an 11/16" MC, which will give a hydraulic ratio of 13.4:1.
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