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Discussion Starter · #1 ·
I have searched here and many other places for a how to guide to putting a dual disc setup on a cb350, but I have had no luck. I know this is probably a fairly common upgrade for these bikes but I have no idea exactly what the process is or what parts are required. Most of the posts I have read say you can use cb550 triple trees/forks? but since they didn't come with dual discs I still don't understand how they work.

Can anyone lay it out for me? Go ahead and assume I'm a dumbass (I'm sure you will anyway). Or point me to a post where my question has already been answered.

Thanks!
 

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Discussion Starter · #4 ·
I know that unsprung weight is something you want as little of as possible on cars, so common sense would say its probably worse on bikes. I didn't know if the added braking ability would be worth the weight gain, and there seems to be more people out there doing dual disc upgrades than single disc upgrades, however I think a single would be more than adequate for this bike. If there was a simple way to get rid of the old single piston I would sure like to hear it!

Thanks
 

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Discussion Starter · #5 ·
I know that unsprung weight is something you want as little of as possible on cars, so common sense would say its probably worse on bikes. I didn't know if the added braking ability would be worth the weight gain, and there seems to be more people out there doing dual disc upgrades than single disc upgrades, however I think a single would be more than adequate for this bike. If there was a simple way to get rid of the old single piston I would sure like to hear it!

Thanks
 

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Yea and between 25 and 40% of the adult population has herpes. That doesn't make it right or desirable.

You need to think in terms of the bike as a system.

I think there's books about that shit, maybe try the internet, more than I'm going to go into right this minute.
 

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Yea and between 25 and 40% of the adult population has herpes. That doesn't make it right or desirable.

You need to think in terms of the bike as a system.

I think there's books about that shit, maybe try the internet, more than I'm going to go into right this minute.
 

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Discussion Starter · #8 ·
That was IMMENSELY helpful. Do you really think I would subject myself to the eternal flow of bullshit that is the caferacer.net forum unless it was a last resort? Yes, I have tried the internet. The internet is not as helpful as everyone believes it to be. If I had been able to find the information I needed I wouldn't be here having this conversation with you.
 

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Discussion Starter · #9 ·
That was IMMENSELY helpful. Do you really think I would subject myself to the eternal flow of bullshit that is the caferacer.net forum unless it was a last resort? Yes, I have tried the internet. The internet is not as helpful as everyone believes it to be. If I had been able to find the information I needed I wouldn't be here having this conversation with you.
 

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quote:Originally posted by RJB

I know that unsprung weight is something you want as little of as possible on cars, so common sense would say its probably worse on bikes. I didn't know if the added braking ability would be worth the weight gain, and there seems to be more people out there doing dual disc upgrades than single disc upgrades, however I think a single would be more than adequate for this bike. If there was a simple way to get rid of the old single piston I would sure like to hear it!

Thanks
This.

The reason more people don't do single disc upgrades is that they require machining of spacers for the rotor and bracket for the caliper.

I think that most 350 guys are more interested in fork upgrading than more brake. The 550 trees and tubes with some other bike's lowers and rim or something maybe? I have no idea. 350 guys, set us straight.

Anyway, whatever the setup is, it is likely a bolt on once you have the right parts. Such is NEVER the case in attaching say floating rotor and modern caliper.

I split the difference on my XS650. Newer calipers, old rotors. Dual disc. Had to make brackets for calipers, but rotors bolted right on.
 

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quote:Originally posted by RJB

I know that unsprung weight is something you want as little of as possible on cars, so common sense would say its probably worse on bikes. I didn't know if the added braking ability would be worth the weight gain, and there seems to be more people out there doing dual disc upgrades than single disc upgrades, however I think a single would be more than adequate for this bike. If there was a simple way to get rid of the old single piston I would sure like to hear it!

Thanks
This.

The reason more people don't do single disc upgrades is that they require machining of spacers for the rotor and bracket for the caliper.

I think that most 350 guys are more interested in fork upgrading than more brake. The 550 trees and tubes with some other bike's lowers and rim or something maybe? I have no idea. 350 guys, set us straight.

Anyway, whatever the setup is, it is likely a bolt on once you have the right parts. Such is NEVER the case in attaching say floating rotor and modern caliper.

I split the difference on my XS650. Newer calipers, old rotors. Dual disc. Had to make brackets for calipers, but rotors bolted right on.
 

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quote:Originally posted by RJB

That was IMMENSELY helpful. Do you really think I would subject myself to the eternal flow of bullshit that is the caferacer.net forum unless it was a last resort? Yes, I have tried the internet. The internet is not as helpful as everyone believes it to be. If I had been able to find the information I needed I wouldn't be here having this conversation with you.
Well fuck you then.:D

You don't even understand the forces involved and their effects on other aspects of the bike. Which is what I was trying to get you to wrap your head around.
 

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quote:Originally posted by RJB

That was IMMENSELY helpful. Do you really think I would subject myself to the eternal flow of bullshit that is the caferacer.net forum unless it was a last resort? Yes, I have tried the internet. The internet is not as helpful as everyone believes it to be. If I had been able to find the information I needed I wouldn't be here having this conversation with you.
Well fuck you then.:D

You don't even understand the forces involved and their effects on other aspects of the bike. Which is what I was trying to get you to wrap your head around.
 

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True, twin disks look cool and a decent set of modern disks have enough power to bend the forks and the frame but why do you want more brakes than teh bike can use?

We have a couple of racing Yamaha twins one with a TZ single disk and the other with an RD400 disk and both can slow from 140+ with absolutely no trouble. And those are old designs.

On good single disk is more than enough and is much lighter than twin disks. There are ways to improve a stock Honda brake, and if you really want better brakes, consider changing the disk and caliper (and forks) to use something more modern. Say a CBR900RR disk rotor with say a CBR600F2 single sided caliper on a better set of forks.

I am not saying you should do that, just suggesting an alternative solution if you really want to change it.
 

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True, twin disks look cool and a decent set of modern disks have enough power to bend the forks and the frame but why do you want more brakes than teh bike can use?

We have a couple of racing Yamaha twins one with a TZ single disk and the other with an RD400 disk and both can slow from 140+ with absolutely no trouble. And those are old designs.

On good single disk is more than enough and is much lighter than twin disks. There are ways to improve a stock Honda brake, and if you really want better brakes, consider changing the disk and caliper (and forks) to use something more modern. Say a CBR900RR disk rotor with say a CBR600F2 single sided caliper on a better set of forks.

I am not saying you should do that, just suggesting an alternative solution if you really want to change it.
 

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I love that herpes is the default metaphor for CR.net these days.


RJB, cool your jets.....you are getting your help so scoop the sand out of your vag and listen up.


Asking questions that have multiple answers and expecting one answer is not going to help you. So let's run back to the project planning stage for a second.

At this point I will remind you that your brakes are only as good as the traction your tire has. The single disc has the ability to lock up on a stock bike, but it takes effort and there isn't a lot of feel up at that top range. The stock drum has a lot of fade and generally any disc conversion is considered an upgrade. What you want ideally is the ability to easily use the entire range of your brakes from light touch to locked up with the maximum amount of feel.

but before we get to the good stuff I will answer your question about the cb550/450/750 dual disc conversion. You are correct those bikes did not come from the factory with dual discs. However honda at one time planned a dual disc conversion accessory kit for all three bikes and did at one time sell one for the 750 for a breif period. The forks have lugs for both discs and basically you convert a stock one sided caliper bracket to bolt to the other side by shaving one of the mounting points and making a spacer for the other. You also reverse the caliper by pulling a crush pin in the caliper so the line exits the opposite side. Search cb750 dual disc conversion and you will find tons of articles on it, the 450 uses the same caliper and fork legs but are shorter, the 500/550 uses similar pieces and the method is the same but only the wheel interchanges. The 450/500/550 forks are preferred over the 750 since the forks are shorter. We will talk about how to mount them up later.

There are two major approaches to improving your bikes braking which is what I assume what you really want to do. A lot of it depends on how the overall bike is setup. If it is closer to stock I would almost say take the weight penalty of dual discs and bigger forks just because it a) looks more impressive, b) is going to add more rideability, and C) you are understressing components which are normally used to working on heavier bikes.

But let's talk about the first approach for a second. The lightness approach or the understressing method. If your bike overall is 50-100 lbs lighter than stock or more (if that is possible) then it may behoove you to work the lightness to your advantage. The simplest way is to get a cb360 disc front end (same as the 350G) and slide it right into your trees. Since the 33mm forks are pretty spindly I would add a fork brace, a tweak bar bolted under the bottom clamp (a fork brace bolts to the sliders, a tweak bar bolts to the fork tubes in case you don't know the difference), an aluminum rim (18"), braided hoses, and a modern master cylinder with a piston size 14mm or one size larger than that. Make sure your fork springs and rear shocks are paired nicely and setup for your weight.

What you gain is braking improvement by making your overall package work less hard. The only unsprung weight you add is the fork brace, and you remove the heavy drum. You get rid of brake pressure loss due to hose flex by using braided lines, and the new master works like a new master so you probably get back some efficiency there. Plus you keep your stock speedo gauge and because the 360 one has the same ratio as the old one and you just run a cable.

What you lose is the increased rigidity of a thicker tube front end and the ability to get better parts like cartirdge emulators and cheap mass produced fork springs.


If your bike is closer to stock weight (and by now I hope you have figured out you need to be weighing your bike), then while the above approach will work it won't improve the handling, won't improve the feel too much, and you will still be stressing your components as they were stock, which means the brake will feel shitty.

Enter the neck bearing chart:

http://scandalon.com/2009/06/motorcycle-steering-stem-bearing-size-chart/

cb350 uses: Upper: 26 x 48.5 x 15.2 Lower: 30 x 50 x 14.4

Honda CB450/K1-K7: Upper: 26 x 48.5 x 15.2 Lower: 30 x 50 x 14.4

Honda CB550K/K1: Upper: 26 x 48.5 x 15.2 Lower: 30 x 50 x 14.4

Honda CB750K (1969-1978): 26 x 48.5 x 15.2 Lower: 30 x 50 x 14.4

See a pattern here? Unfortunatly what you don't see is that the stem heights are different for all three bikes, with the 450/500/550 being the closest to the cb350 stem height. You will still have to make a spacer that fits under the top clamp to allow the nut to tighten down properly, and you will have to measure that yourself, but basically you bolt the entire front end Triple trees to tires right into your 350 neck. You will also need to make new steering stops - you can buy dirt track bolt on ones, or you can drill and tap the stock stops in the clamp and put a bolt in there. either way, it is pretty easy. Now you can stop here and already you would be miles ahead of the game, however, if you got a 450 front end you can search out a hondamatic 750/ GL1000 front rim and upgrade to alloy. You can also run braided lines. Again, better springs, maybe cartridge emulators, and a fork brace. no tweak bar unless you really want it. But even stock the components on the bike will be underworked and will be an improvement over your stock 350 stuff. It is at this point if you really want to go overkill you can do the dual disc converion that many 450/500/550/750 owners have done for 40 years.

As with anything nobody is gonna write you instructions. It isn't fair to us or to you who needs to learn not just how to do custom work but how to be brave enough to plunge into custom work with little more than a well reasoned idea of how it goes together.
 
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