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I don't believe the OP will have any idea what your talking about.
Possibly :|

Bottom line is; that would be a suspension downgrade. Manufacturers use the directly connected shock on top of the swingarm to save money not to make it work better, the lower mounted linkage type shock works far better and is featured only on the more expensive performance oriented motorcycle models.
 

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what you need to do, at the very least, is draw a line from the swingarm pivot to the lower shock mount. then another from the lower shock mount to upper shock mount. the angle between them must be less than 90 degrees all through the travel to make it at least somewhat decent. the angle should get bigger the closer it gets to full compression. that will give it a slightly increasing rate. as below.

xj900 cantilever.png

it generally means the upper shock mount needs to be a lot lower than people expect or make them.
 

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Discussion Starter #43
Thanks. Yes i check the angles its all good the angle is less then 90 at Full travel. I am keeping the same top mount forward point on the main frame and turning it 90degrees up and the back point of the top mount(currently the bottom rear bar) moves up to under the fuel tank creating a new top bar position. Its not a daily ride, its not meant to practical. Its a scrambler design. im stripping the whole bike im left with the rear swing arm and carbs then i can remove the engine from the frame.
http://www.yamaha-motor.com.mx/Manual_Partes/Catalogos/Deportivas/XJ900 Police/5JD2_2000.pdf

i have the manual helps

By then all cad drawing should be ready for the new sub-frame Made from 5mm plate

5mm metal plate.jpg

This is the Goal

Yamaha XJ900 vision.jpg
 

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Thanks. Yes i check the angles its all good the angle is less then 90 at Full travel. I am keeping the same top mount forward point on the main frame and turning it 90degrees up and the back point of the top mount(currently the bottom rear bar) moves up to under the fuel tank creating a new top bar position. Its not a daily ride, its not meant to practical. Its a scrambler design.
Scrambler ->



You are building a .... i better not say :|
 

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I would suggest that you ignore the XJ600 idea and focus on welding in two lower rear sub frame rails to connect to the rear of that shock mount. Play some more with photoshop or pen and paper to work out where the tubes could/should go to look elegant and still add sufficient strength.

You do not want to add thick, heavy steel plates which have very little strength or stiffness but add lots of weight.

Option 2: Weld the part you cut off back where it came from.
 

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Discussion Starter #46
Thanks for the advice. taking all into consideration im looking at if i can rework the linkage system and keep the bottom linkage system but redesign it so i can get the shock to come up and closer to the main frame, Like in the FZ1. Dont worry guys i have still not cut up the bike its still okay with all in place. still designing.

Any advice on how to rework the linkage system please advice
I have figured some of it. i gotta re-design similar to image to get my bottom shock mount to come as high as possible give me a new top mount position closer to the frame and higher. sort of like using a raising kit
linkage.jpg
 

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Hey, I'm just passing by and I'd like to throw in my 2 cents.

I fear I cannot help you much on what looks like a general downgrade of the bike's characteristics to me, but I just wanted to say that I find it really sad to buy a bike and start modding it hoping that in the end it will look like someone else's bike.
Don't you have more original ideas? You sure you need to copy someone else?
Also reading the thread looks like you are waiting for people here to build the bike for you.

Just my opinion :)
 

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The original linkage design carries the weight low because the mount points and the shock body are low in the frame, that's a performance plus.
The ride height as well as the load rates are so easy to adjust by simply replacing the 2 small triangle brackets, it's almost ridiculous how cheap and easy it is.
It's the exact same suspension setup used on the most competitive trials motorcycles and companies like Jitsie sell little aluminum plates for that exact purpose, to raise or lower the rear of the bike. Trust me you don't want to throw it away, you have too much going on there to discard for all the wrong reasons, just keep all the bearings properly serviced and that setup will function far better then anything you could possibly cobble up.


Proper term for the triangle plates is the Delta linkage and the simple term for the aluminum bar with the bearings in each end is the Dog Bone.
 

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Discussion Starter #49
Im here trying to get ideas cause i got a bike that its really the best to be modding and there is hardly any Xj900s done well. Im looking for people's experience and advise. I like the concept or a modern tarmac scrambler. im not going to be going off road i live in Dubai its dry, smooth roads. So thats why i like that idea of the War Machine. I can not achieve the same look but only using it for a concept
 

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Discussion Starter #50 (Edited)
The original linkage design carries the weight low because the mount points and the shock body are low in the frame, that's a performance plus.
The ride height as well as the load rates are so easy to adjust by simply replacing the 2 small triangle brackets, it's almost ridiculous how cheap and easy it is.
It's the exact same suspension setup used on the most competitive trials motorcycles and companies like Jitsie sell little aluminum plates for that exact purpose, to raise or lower the rear of the bike. Trust me you don't want to throw it away, you have too much going on there to discard for all the wrong reasons, just keep all the bearings properly serviced and that setup will function far better then anything you could possibly cobble up.
The picture i posted is not my linkage set up. i will just raise the shock with a raiser kit and just keep the shock as it is maybe upgrade for more stiffness. idealy i would like to move the top mount of the shock closer to the main frame so i can create any design in the sub frame. Is to create new delta linkage and dogbone to be able to tiltl the shock forward and slightly up to mount it on the main frame
IMG_20190507_0012401.jpg

My issue i am facing is how to get rid of this bottom bar
IMG_20190507_001240c.jpg

Can i remove it and put a support from the top of the shock mount to the top bar
7.jpg
 

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:| you really need to start working on what you have and not on what you wish you had.
Buttress what you have without altering the mounting points and dimensions in the least, the sub frame does nothing except give you somewhere to sit your ass and originally yours was also designed to carry a passenger. Beyond that it carries lights to make the thing street legal at night and a rear fender <- which believe it of not is a vital part of a motorcycle, if it wasn't there would not be fenders on a trials bike.

+ ... that crankcase breather pod filter is a total stupid idea. Don't copy yet another stupid idea.
Learn what has to go in and out of that breather vent and put something on there that will work.



;) I kind of figured out where you live by your user name,
your roads suck just as bad as the roads here suck, we just have a lot more of them.
 

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Sidenote on replacing the rear shock, if your shock is working leave it. There are 4 critical aspects to a rear suspension coil-over shock: spring rate, compression dampening, rebound dampening and spring preload. "stiffer" is what somebody who doesn't know any better thinks is an upgrade, a true upgrade would provide you with adjustment over all of those aspects if your current shock and spring does not already accommodate those.
... plus your bike was designed to carry 2-up and you are making it into a solo bike, your spring rate is going to be plenty high enough unless you are a really heavy person.
 

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... Can i remove it and put a support from the top of the shock mount to the top bar
Don't cut more off and think triangulation. The triangle is a very strong shape and is repeated throughout your original frame. Replace triangle shaped supports with similarly triangle shaped supports and it won't fall to pieces like a stack of cards. The loads from your rear suspension, you and all the weight is headed for the steering head bearing and support. That is the most highly stressed part on the frame.
 

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Discussion Starter #54
If i move the top mount of the shock forward to the main frame there wont be a need of the existing sub frame which like u said was designed for carrying two, storage boxes and a whole load. by reducing the dog bone i can get the shock to raise n move forward( like using a raising kit) The shock is good n i dont want to replace it. Lol the pod filter on the crankcase came from the previous owner not my doing
 

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Discussion Starter #55
Damn this has been a crazy up and down but i think i finally got it. The top mount of the shock sits in a U bar which the front is mounted to the Main Frame and the back to the Bottom bar of the Sub-Frame.

IMG_20190507_001240.jpg

After a lot of thought and every ones in put i decide not to move the shock at all but to install a straight longer 55cm U bar at the same angle making my new sub frame

IMG_20190509_020946.jpg
IMG_20190509_020950.jpg

After this i mocked up the side plates and bottom plate and i think im happy let me know what you think

IMG_20190509_023130.jpg
IMG_20190509_023416.jpg
 

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Not understanding - what are those lower cut off bars going to tie into? The bottom of the cardboard? If you just leave them hanging in space with no support from above then they will be touching that cardboard after you hit your first big bump.
 

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i think he's going to cut them off and put a vertical piece on top of the shock mount to the frame work above.

as i understand it anyway.
 

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Discussion Starter #58
I am going to totally remove the lower bar and and mount the shock in the new C channel i am going to install making my new lower bar. i am not using any of the extisting sub-frame. i am making a whole new subframe
IMG_20190509_020950.jpg
 
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