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Fighter 4 Christ
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794 Posts
Discussion Starter · #1 ·
Hey guys/girls. Been awhile...Not entirely fighter related but IS a suspension question. i come here because i TRUST the monkeys here

This is my 79 xs650...going monoshock. I just bent up a tube and mocked up the shock. My idea was to have the shock and respective forces in line with the top neck of the frame. There was logic only in my mind about this and was not based on any engineering experience, since i have none.

My question is.....am i right? Should i leave it as is, or what are the recommendations?
TIA!
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my Howron Bender



Wheel is pushed forward all the way so i have nice clearance when the chain is adjusted out....good plan? or wrong?


It's a bit off, but i figured would need to tweak it a bit since i don't know how it will look loaded on it's own weight and with my butt on it. How does one adjust for this during the beginning phase of building???



thanks all!!
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This is just my opinion but based on a little experiance from a long time ago

I think as it sits now once the full weight of finished bike & rider are on there & you hit a bump the bottom (rear) of the shock is going to want to go up or down as much as its going to want to compress the spring, i hope that makes sense

imho the bottom of the shock needs to go up so that the shock sits more horizontal to the ground i know this means making a new loop on the swingarm or lifting the one you have but i really dont think the shock will work at the present angle

Also what shock are you using ? if its off a rising rate suspension setup theres little chance of it being the right spring or damping rate for your application, you realy need a shock of a cantilever setup from a bike of a similar all up weight

Hope it helps
 

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Fighter 4 Christ
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794 Posts
Discussion Starter · #4 ·
i believe it is from a 1992 GSXR 600W. Correct Johnny? no clue as to it being a rising rate shock....absolutely no clue.

I'm open to adjusting as necessary. I don't want to die just because of an angle mistake, it's gotta be something better that kills me.

How much more horizontal should it go though?
 
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As above with regards to the shock itself, i would find a direct link (cantilever) shock off a bike of a similar weight to what you are building

I would say you need to lift the bottom/back of the shock 2 or 3" to have a good chance of it working, thats presuming a diffrent shock btw, you will also need to tie the new loop back down to the original swingarm in a couple of places, i would do this with a couple of tubes, one either just inside or outside of the chain run & a matching one the other side

If i was doing this myself i would weld a slightly wide top mount in the position you have it, i say slightly wide to allow for a wider fitting shock if needed, you can always shim it out later
Next i would heavily tack the new loop & supports along with the rear shock mount then get a fat mate to jump up & down on it while you watch which should give you some idea of if it will work & the movement available
 

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Fighter 4 Christ
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794 Posts
Discussion Starter · #7 ·
Dammit so scrap this shock? Any ninja 650 shocks laying around guys? I have raised the top loop 4" to close the angle more acute than 90 degrees as another had suggested. Good idea on the shock mount tabs and shimming. I like that idea. I had planned on bracing the top tube more like you said, was tacked in place more to illicit feedback on angles which is so far very helpful thanks to you guys.

Would eBay dirt bike shocks do the job? They are designed for 125cc bikes though.....8.5" ones and 10" ones are available. The longer ones just won't fit....so no way I can get this shock to work....even if I fad a better mount?
 

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.... the rear shock mount then get a fat mate to jump up & down on it while you watch which should give you some idea of if it will work & the movement available


buy beer for your mate incase it breaks and he falls...he may not be happy


and as for the dirt shocks i wouldnt
i dont remember which gen cbrs have a direct link shock, but thats another option.
 

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nah people do that shit sometimes but we just like to preach the correct way so that it functions as it should

http://www.ebay.com/itm/08-2008-Kaw...Parts_Accessories&hash=item1c3ec758cd&vxp=mtr

not too pricey, id just get a shock designed for the application for piece of mind sake though

The linkages were originally designed to allow more shock travel in a limited area and allow a changing effective spring rate with the swingarm travel

im not positive how much difference in spring rate they have but i do doubt its the same.
 
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It wont hurt to try it but i think you will find its super stiff in this application & there is now no rising rate, i could be wrong but theres only one way to find out ;)
 

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Fighter 4 Christ
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794 Posts
Discussion Starter · #17 ·
ok 2 questions...

i have the mount mocked in a way i saw another xs650's monoshock mounted. the tabs on the side of the top brace tube rather than infront of the bend. at a 90degree as you see above. is this ok?

and second question is how do i mount it. do i need to preload the suspension? i am leaving the shock adjusted in the middle so i have equidistance forward/back if necessary once actually mounted. but i have the front frame on blocks, and the rear tacked in place to hold the swinger straight. do i need to slightly hyperextend the swinger's angle so once fitted it sits straight under weight? how should i go about it?
 
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For the top mount welding it to the side of the top tube is fine but rather than making the mounts square as in your pic i would make the follow the curve of the top tube giving you more area to weld, i would also cut a piece for the front to also weld to the top tube & tie the 2 sides of the mount together

The second question may require some trial & error to get it right but basically yes you need to allow for some suspension sag when setting it up & welding the mount i would start at around 15 to 20mm tack it well then get some weight on it & see what you have as mentioned before

Hope it helps
 
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