Yamaha rd350 Road Racer Liquid Cooled!!

Re: Yamaha rd350 road racer

hurco550 said:
Cool thanks! Link is invalid though, is that katana?
Yeah, Katana. They were on GS, too. Plus a bunch of others. Marauders, Intruders, etc. I typically search Katana for both sides.
 
Re: Yamaha rd350 road racer

hurco550 said:
Good to know! Planning on running a single fzr rotor with some kind of modern 2 piston caliper. Should be plenty for as light as I'm hoping this bike will end up. I was contemplating running the caliper behind anyhow. I don't know, but the extra stopping ability makes me nervous as far as pulling on the mount tabs.seems like pushing would be better, but on the same coin I've never seen any brake off. May be over thinking it, but I don't know if there is any benefit performance wise to shifting the weight of the caliper back vs. Front?
In fact there is a benefit.

(from another thread)
"There is in fact a very good reason for locating the calipers behind the fork legs rather than in front. The goal is to reduce the moment of inertia for the entire steering assembly. More technically the polar moment of inertia, the idea is the combination of mass and distance around a point of rotation. This is the difference you perceive between a very heavy door and a lighter one when you swing it open (or closed). The two doors appear to be identical, but the heavy one will take more effort to get moving and likewise coast a lot further (or slam better if you like). Alternatively, you could have a much bigger door, but if correspondingly lighter, it would seem the same as the smaller heavier door. You can look at the front end of your bike like a door with the hinge at the steering pivot, and the width of the bars, the weight of the controls, the diameter and weight of the wheel and weight and location of the brakes etc. etc.being the weight and size of the door.
This impacts steering, though not as some might expect. Having a super light steering assembly will indeed affect the steering, but only noticeably at parking lot speeds. The geometry (rake and trail) is really more important for how heavy or light the steering feels at any speed.
What is very important is this: All things have a natural frequency at which they will oscillate. Heavy things oscillate at lower frequencies, and lighter things oscillate at higher frequencies. Think tuning fork. This is the ringing you hear when you drop a coin. A similar phenomenon is present in assemblies with multiple components in motion. The natural frequency at which your steering assembly will oscillate is determined by many things, but primarily it is a function of its mass and how that mass is distributed in relation to its axis of rotation. You can increase the natural frequency of your steering assembly by making everything lighter, by making it more rigid, or my reducing the moment by moving weight closer to the axis of rotation. So moving those heavy brake calipers back behind the fork legs will move them closer to the steering axis, reduce the moment of inertia and cause the natural frequency of the whole assembly to increase. Making the wheel lighter, narrowing the bars, removing hand controls etc will have the same effect.
So why do you care about the natural frequency of your front end? You don't unless that frequency is able to get started by your operation of the bike. The coin in you hand does not start ringing by itself, but you can get it started by dropping it on the table. There is rather a lot going on with the front end of your bike when rolling down the road, and if the road were perfectly smooth, the tire perfectly round and if the rider never moved around on the bike all would be well at all speeds. However this is not the case in real life. Say you are traveling along at 100 mph on a smooth road and you hit a cigarette butt. This will deflect the tire a very tiny bit. The geometry of the steering system is inherently stable with the contact patch of the tire dragging behind the steering center generating forces that are enormous compared to the deflection so the steering returns to center and you never notice - but maybe not. There is mass in the steering. When the forces created by the steering geometry try to return the steering to straight, the mass wants to keep going and the assembly is deflected in the opposite direction. This is akin to the motion of one cycle of oscillation of the natural frequency of the assembly. At low speeds, this takes place at at a rate below the assembly's natural frequency, and without another cigarette but perfectly timed to follow the first the oscillation decays out. But as you travel faster and faster, the time it takes for this motion to be completed gets closer and closer to the natural frequency. At some speed, that tiny deflection will match the frequency of the assembly, and every swing of the steering returning to center will be helped along by the natural frequency of the system. The deflection you didn't even notice when you hit that cigarette will become larger and larger as long as the speed and the corresponding rate at which the geometry can return the system to neutral (straight ahead) matches the natural frequency. The dreaded speed wobble. Speed up, and the return to straight speed of the geometry falls out of sync with the natural frequency and the wobble goes away (of course you will have to slow down back through the danger zone eventually), or slow down for the same effect.
The world being what it is has conspired to make the typical natural frequency of a bikes front end be right in the range of typical top speeds. So if your bike tops out at 110 mph, and the moment of inertia and stiffness of your front end make for a harmonic at 100 mph, your effective top speed is a bit less than 100 mph because it will be obviously dangerous at the frequency matching 100 mph.
Reduce the moment of inertia by moving those heavy calipers considerably closer to the steering pivot, and the natural frequency will go up noticeably. Maybe it now takes 120 mph to match it. Now you can cruise safely at you top speed of 110 mph because the matching harmonic speed of your front end is out of reach."
 
Re: Yamaha rd350 road racer

deviant said:
Yeah, Katana. They were on GS, too. Plus a bunch of others. Marauders, Intruders, etc. I typically search Katana for both sides.
Dang, those are stupid cheap. And since you've done it I assume you don't run into many issues with spoke clearance?
 
Re: Yamaha rd350 road racer

hurco550 said:
Dang, those are stupid cheap. And since you've done it I assume you don't run into many issues with spoke clearance?
Zero. So far I've done it on a KZ front end, a GL front end, A VZ front end (dual disc conversion) and a CB750 front end.
 
Re: Yamaha rd350 road racer

jpmobius said:
In fact there is a benefit.

Thanks for the info jp! I have read that about 3 times now, still digesting all of it. the info is appreciated!
 
Re: Yamaha rd350 road racer

I'm using the FZR caliper and rotor on my RD. It's the RD hub, but FZR forks. I'm sure the FZR caliper can be made to work with RD forks, but I bet the spacing is going to be a little tricky. The caliper is quite close to the spokes, even with the rotor spaced out.
 
Re: Yamaha rd350 road racer

And the same or similar are fitted to SV650 and that's what I fit on wire spoke wheel GT750s with adapters.

Double sided ( pistons pushing from both sides) are hard to fit because they hit the spokes in most cases. Stock RD calipers fit and clear the spokes but they are really heavy - 1,536gms without pads compared to say an SV650/Katana caliper at 816gms without pads according to my notes. And the disks are also very heavy on an RD at almost 3Kg each compared to say 1.300 gms on a CBR600. There are pounds to be saved right there.
 
Re: Yamaha rd350 road racer

And pounds to be saved in especially good locations!
 
Re: Yamaha rd350 road racer

Working through making my own rearsets. Got some heim joints and aluminum round to start.
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I was going to go with an all joint setup similar to this.
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But I think it will be way lighter and simpler to go with a cable setup running to the rear drum. May try to use a ready made cable, like for a gt250 (and I have one handy for measuring.
 
Re: Yamaha rd350 road racer

And the beauty of dtt, a few have been shared here. Gotta love when Google searches lead back "home".
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Re: Yamaha rd350 road racer

Haha. XB posted that Yamaha race bike on my Freeze-dried hellride CB360 thread when I was designing my rear brake setup for the clip ons on that bike.
 
Re: Yamaha rd350 road racer

Good for you! (I like cables -though they have some issues). Very satisfying building foot controls I think - very plain to see the mechanism, and you use it always, so you get some satisfaction of a job well done every time you ride your bike. Take some time to understand the kinematics of the mechanism(s) and you will be well rewarded with foot controls that work really well. If you like how the stock set up works, it is pretty easy to create new controls in a new location that work very much the same. So keep all your original parts so you can measure them and create new controls that will give you the same function. For example, your rear brake has a very simple pedal that operates a crank arm that pulls a rod that in turn operates another crank arm that turn a cam that pushes the rear brake shoes against the drum. Very likely you will keep the cam and crank arm that is part of the rear brake assembly, so if you wish to keep the same "feel" of the rear brake, you simply need to keep the same ratio of brake pedal length to pedal operated crank arm in your new system and you can't go wrong. The stock pedal is really long on an RD, but it does not matter. It is the ratio of the pedal to the arm it operates that counts. So if you design a shorter pedal, make the crank arm that pulls the cable correspondingly shorter. Follow the same notion on your shifter design and your new controls will work well.

And you may ask "What issues with the cable?!!". Cables tend to be stretchy and have "lost motion" due to convoluted routing. The obvious solution is to 1) Make a very stout cable and housing so any "stretchy" feel is rendered unnoticeable, and 2) make the routing as close to straight as is practical. The lost motion happens because there is considerable slack between the cable and its housing. If you need to put a lot of force on the cable, it has to ride tightly against the housing and take up whatever slack was present before it can work with authority. You can see that I addressed both of these issues in the pic of one of my bikes that you presented.
 
Re: Yamaha rd350 road racer

One we prepared earlier.

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Drum is R5 or RD- originally a rod type. Welded on a new cable boss and cut down the backing plate. Frame is TD3/TZ250 and cable was GT750 Suzuki. Much easier than all those linkages. You could also look at a CB160 rear brake cable.

For the gearshift, use male heim joint inside aluminum tube. It's much stiffer that 1/4" rod even if you have to bend it. If you get fancy you could use left and right threaded heim joints but I don't have a left hand tap, so I use 2x right threads.
 
Re: Yamaha rd350 road racer

hurco550 said:
And the beauty of dtt, a few have been shared here. Gotta love when Google searches lead back "home".
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TZ or TD/TR rear brake. Heavy as all get out but they look soooo sexy.
 
Re: Yamaha rd350 road racer

I think I may have a solution that is looking pretty solid at the moment. I started looking closer and measuring my Suzuki gt250 cable type rear brake. Dimensionally it looks very very close to the Rd hub, and it has the lug and everything already for the cable. At one point I had another gt250 rear wheel kicking around, but I'll have to go out and dig around at my dad's place to see if it's still there. May be able to make this whole rearset deal look close to a "factory" type setup.
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Re: Yamaha rd350 road racer

Quick auto cad drawing. Mounting brackets will also have slotted slip joints for the chamber mounts, and will be made from 3/8" thick 6061 aluminum.
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None of the geometry is right, but here is an idea on the lever as well.
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Re: Yamaha rd350 road racer

VonYinzer said:
Damn you people and your fancy new fangled 'rithmatic machines.
Lol not very new, it's called draftsight, and it's basically a free version of autocad 98
 
Re: Yamaha rd350 road racer

Well, went over to my dad's place and dug around in the haymow. I found the extra gt250 wheel. Got back to the garage and did a bunch of thorough measurement to see about doing the wheel swap. I got the Rd wheel about pulled off when I thought that I may get lucky and see if just the gt250 brake plate would fit in. Well I'll be darned it does. Almost a direct "bolt up". Same drum diameter, same axle size, same pad width the whole 9 yards. The only thing that is different is the steel bushing is a tad longer that is pressed into the plate and seats against the bearing. That can be remedied with a small spacer, otherwise it's dang near drop in.

Rd left, Suzuki right.
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Now I have a plate with the cable mount already cast in.
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Only other thing is the stay offset. I can bend the stock rd stay or fabricate a new one easy enough.
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I'm assuming that the hubs and brakes for some of these old Jap bikes must have been contact work or bought from a supplier as close as the design is and even dimensions. Kinda like showa forks ect.


Oh, doesn't look like I'll be able to re use my Yamaha pads :/
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