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Twin front disk conversion. 20 Nov 2023 14:43 #891884

  • Jokinarnya
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Evening all. 
My 82 KZ550 ltd currently has a single front disk which has had it. 
 that got me thinking about a twin disk conversion.
I have the chance to get a kz1100 wheel with disks for a reasonable price but would it fit? Or are the forks wider on dual disk forks? 

If it would fit, my forks have caliper mounts on both legs. So other than a caliper, would it be a splitter and mastercylinder to convert over? 

Thanks
1982 Kz550 LTD

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Twin front disk conversion. 20 Nov 2023 16:06 #891889

  • Nessism
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You might want to take a close look at your front wheel.  It may already have the mounting provision for the extra disc.  

Regarding the caliper, you will have to find one with the proper hanger.  Frankly, I'm not sure if it exists.  Hopefully someone here will have a better answer.

For a master, you will want one with a 5/8" bore.  For lines, you can skip the splitter, and simply run two full length lines.  On, some modern bikes, one line runs to one of the calipers, then a second line jumps over the wheel to the other caliper.

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Twin front disk conversion. 22 Nov 2023 06:18 #891946

  • martin_csr
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On EB I'm seeing 1100 wheels that are 19 X 1.85 which is the same as the 550Ltd, so it may fit fine. My neighbor put a KZ1000 Fr wheel on his KZ650-CSR. the csr has the same size wheel as a 550Ltd.  I think the 1000 wheel he installed was a 19 x 2.15. The speedo drive gearbox didn't fit right, so he had to rig the speedo cable but I forget exactly what he did. 

Guessing on a brake caliper, but probably a KZ550-D1 GPz or KZ750H Ltd >> from the diagrams these models have the same calipers.  also the 1000K/M Ltd/CSR models.  Guessing on the fitment because the GPz550 has the same steering stem as the 550Ltd. also, you may need to swap out the LH brake pads w dual disk brake pads.

Another consideration is that the dual brake disk rotors can be smaller than single disk. If your forks will accept a RH caliper, you may need to get a second 550Ltd disk. measure yours beforehand and get the measurements of a donor disk.

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Last edit: by martin_csr.

Twin front disk conversion. 21 Dec 2023 11:25 #892989

  • SgtTimmyusmc
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can any one weigh in on doing this to a 750b twin? id love better braking, because at the moment i think my rotor is warped......

not tying to hijack a tread, just same question, differnt application. 
1977 kawasaki kz750 twin.
2022 honda trail125.

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Twin front disk conversion. 23 Dec 2023 08:19 #893055

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750-Twin. An internet search yielded multiple topics using the following search:
Internet search >> site:kzrider.com dual disk conversion steell
I only looked at one of them linked below, but it has some specific info for your application.
kzrider.com/forum/5-chassis/237489-conve...t-brakes-on-79-kz750

Regarding anything for a 750B Twin. If you see any replies by steell or bountyhunter, your ears should perk up >> both of them know quite a bit about the Big Twins.  steell is probably what you could say is a bona fide expert that range of twin models (76-83). bountyhunter may be as well but I'm more familiar with replies by steell.
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Twin front disk conversion. 23 Dec 2023 08:48 #893058

  • SWest
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If this helps I bought a KZ750G set of mag wheels from Vic. The rotors from a KZ900 front wheel fit and the axels are identical. They also came with a pair of forks in good shape I won't be using. The speedo drive was plug and play. I bought a Axle assy. from eBay for the 750 in better shape to keep the 900 wheel assy. as a set. Same for the rear wheel assy. Now I have a set of mag wheels and a spare set of wire wheels. I like spares.
Steve

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Twin front disk conversion. 24 Dec 2023 06:52 #893094

  • SgtTimmyusmc
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750-Twin. An internet search yielded multiple topics using the following search:
searched  >> site:kzrider.com dual disk conversion steell
I only looked at one of them linked below, but it has some specific info for your application.
kzrider.com/forum/5-chassis/237489-conve...t-brakes-on-79-kz750


Regarding anything for a 750B Twin. If you see any replies by steell or bountyhunter, your ears should perk up >> both of them know quite a bit about the Big Twins.  steell is probably what you could say is a bona fide expert that range of twin models (76-83). bountyhunter may be as well but I'm more familiar with replies by steell.

My searching poweres must be getting weak. Thank you so much!!!!
 
1977 kawasaki kz750 twin.
2022 honda trail125.

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Twin front disk conversion. 26 Dec 2023 21:56 #893158

  • DoctoRot
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Twin disk from kz1000/900 76-80 will fit kz750b. You need the complete setup - MC, calipers, disks. FYI single disk is 7mm+ twin disks are 4.5mm+

alternatively,  a lightweight single disk from EBC, stainless brake line, and some good sintered pads will make single disk brake setup pretty good.

I actually switched back to single disk  setup  on my last kz750B because it shaved something like 2.5 pounds of rotational mass and another 3-4 lbs unsprung mass from the dual setup - made the bike feel more nimble with quicker turn in.

 I was using dual Brembo P108 calipers and a Brembo MC with OEM twin disks and switched to single EBC disk with single P108 and brembo MC, but this will have the same effect with the stock calipers and mc 

IIRC the EBC single disk is like 2 lbs lighter than the stock heavy single disk.  this might not seem much but you definitely feel the weight difference because its so far out from the axis. 

Dual disk is about increasing surface area for heat dissipation more so than increased braking force. 

 
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Twin front disk conversion. 22 Jan 2024 11:21 #894305

  • Rusty B1
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I did a dual disc setup  on my '76 750b . My rotors & right side caliper and hanger were supplied by a friend who does lots of work with vintage Hondas and Kawis
so I'm not sure what model those parts were sourced from.
The rotors are drilled  and milled to 4.5mm .  I used a master cylinder from a 2009 650 Ninja (14mm bore) which also gave me the lever-mounted brake light switch.
Since I got rid of the hydraulic switch I took the  stock 3-way splitter and retapped the hole from the switch to accept a banjo bolt. I mounted the splitter upside down, 
Ran 1 line from the top to the master and a separate short line from splitter to each caliper. I don't doubt that this has been done many times before  but it looks good
and I'm very pleased with how well the brakes work .  I hope it's OK to post a pic here.
Russ
1976 kz750 B1 twin
1978 cb750
1982 cb900F
1998 Bandit 1200
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Twin front disk conversion. 22 Jan 2024 12:18 #894310

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The caliper bore is supposed to be 42mm on singles and duals but i personally have seen some 38mm bores come on the single disk setups - not sure if from the factory or someone swapped it at a later date. Ive even seen dual disk setups where there was one 38mm and one 42mm. Not ideal as one caliper will pinch harder than the other. if you're doing this conversion you should check to make sure they are the same.

The prefered MC size for stock 42mm dual calipers is 5/8" (16mm) but the mechanical leverage ratio on a MC can change the "feel" of a brake a lot and there is variation in the lever ratio between manufacturers. If it works and you like it then there is no problem.

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Twin front disk conversion. 22 Jan 2024 13:38 #894317

  • Rusty B1
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Mine are 42mm . I wasn't aware of the 2 different sizes. I put about 1300 miles on the bike last summer (just got it on the road in April) and so far I'm quite satisfied with the components I have.

 Thanks for the info. If this ever becomes an issue I have access to another MC with 5/8 bore.
Russ
1976 kz750 B1 twin
1978 cb750
1982 cb900F
1998 Bandit 1200

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Last edit: by Rusty B1.
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