SV650 rear shock dogbones question

[Alphamazing]

So I'll be getting a new SV650 rear shock soon, but will be unable to drill holes in the tabs. This is because the tabs won't be there; rather, there will be a tube down with the bolt hole. I'll have to have the dogbones extended/custom made in order to keep the ride height sane.

So, that being said...

How easy is it to have dogbones made?
Where can I get some made for cheap?
How much does it typically cost to have these made?
Would it be best to make new ones or to extend the ones I've already got?
What else do I need to know about getting these dogbone issues taken care of?

EDIT: Just learned that the shock has height adjustability up to 12mm, so it might just bolt in. I'll have to wait and see, but still would like to get dogbones taken care of, just in case.

[JamesG]

I guess you have an aftermarket shock?

Ride height adjustment is usually from stock to +12mm. So the ride height adjustability isn't going to help you.

Look on ebay for a set of late model ZX6R lowering links (the aluminum kind with three holes on one side). These will lower a stock GS about an inch and half. So should return ride height to just about normal. 

Of course leverage ratios might now be all screwed up, but thats just something you are going to have to try and experiment with.

[Alphamazing]

Leverage ratios? Huh? What do you mean they might be screwed up?

Are the ZX-6R lowering links a bolt in for the GS, or will they require some grinding to get them to fit? What about GS lowering links?

[JamesG]

Yes they bolt right on. 
AFAIK no one makes GS500 specific lowering links. You can get a set of threaded dogbones that will allow an effectively infinate adjustability, but they are close to $300 a set.  Having someone machine you a custom pair will also cost something similar.

Post edited because I think I was inaccurate in describing the rear linkage arrangement and am too tired to articulate it right.
Google or search Amazon for "motorcycle suspension" and you can read up on it.

[Alphamazing]

I don't think 10mm will have that much effect on the leverage ratios, if noticeable at all. It'll probably feel stiff just because it's a stiffer spring and shock.

EDIT: Also, I've been reading up on this stuff and it seems to all point to saying that lowering the bike is bad because it changes the steering geometry which can cause weird handling. It also messes with the rear wheel travel compared to the shock travel (the leverage ratio). However, I'll be returning it as close to stock as before, so the steering geometry won't be changed drastically, and the leverage ratio should be close to stock. The change in angle from the stock shock to my SV shock will be .2157^o. That is roughly 5 ten-thousandths of a revolution (0.000599119622 to be exact).

Correct me if I'm wrong, but I don't think that change will produce a noticeable effect on the damping rate of the shock. It is being returned to stock ride-height after all.

[runsilent]

Look on ebay for a set of late model ZX6R lowering links (the aluminum kind with three holes on one side). These will lower a stock GS about an inch and half. So should return ride height to just about normal. 

The Muzzys M1200-SL should work, right?

http://www.muzzys.com/catalog/chassis.html#links

[JamesG]

Thats the very one.

While you are returning the swingarm to close to its original static position, the shock linkage and dogbones are now no longer parallel with the SA.  The shock has the linkage at a more accute angle.

I'm not sure how it will react to be honest.  All the books I have read have always frowned upon tinkering with suspension components unless you adjust all. I do agree that is should be minor and easily compensated at the shock (probably less preload than otherwise).
I guess you will just have to try it.

[Alphamazing]

Those muzzy ones are nice, but they are still $50.  Dogbones look pretty easy to make, it looks like. I'm a mechanical engineering student, so I can design my own using my CAD software and get it to one of the local machine shop junkies and get a set custom made for fairly cheap probably.

The shock has the linkage at a more accute angle.

I see what you mean. However, the SV shock is longer than the GS shock, so the dogbones would not have been at the correct angle anyways. With the lowering links wouldn't it bring it back to normal?

[MarkusN]

The change in angle from the stock shock to my SV shock will be .2157^o. That is roughly 5 ten-thousandths of a revolution (0.000599119622 to be exact).

Correct me if I'm wrong, but I don't think that change will produce a noticeable effect on the damping rate of the shock. It is being returned to stock ride-height after all.

Careful! Progressivity of the spring ratio is caused by the arc that the linkage is describing. Setting that at a more acute angle will make the characteristic more progressive. These linkages can also pretty soon run off to weird angles when lengts of links are changed.

Minor changes are doable, but major ones can quickly lead to a linkage that does not really work anymore.

[JamesG]

I see what you mean. However, the SV shock is longer than the GS shock, so the dogbones would not have been at the correct angle anyways. With the lowering links wouldn't it bring it back to normal?

Hold your hands in front of you (preferably with no one watching)  palm down, horizontal, and a few inches on top of each other.  Top hand is the swingarm, bottom hand is the shock linkage. If you want, put a pencil between the fingers, connecting the two to simulate the dogbones.

Now tilt your lower hand down about an inch so that it has a different angle to the upper. This is what will happen when you install that SV shock. Even if you let the pencil slip between your finger so that the top hand doesn't move, the bottom one is not out of line and the shock's spring has a different leverage ratio linkage vs. swing arm.

See?

[Alphamazing]

I see what you mean. The linkage height won't change by that drastic a distance though, rather, only the .215^o I mentioned earlier. My father says that people on the FZ1 board correct this sort of thing on their bikes by adding or removing preload so that the shock behaves normally.

I do understand what you mean though.

[GeeP]

It sounds like you'll be changing the spring rate somewhat.  I don't have an SV shock here to compare, otherwise I would be more informative on that part of the subject.

However, making the linkages is straightforward.  You know the leverage ratio of the swingarm.  You need to determine the rate of the existing shock spring, as this will allow you to determine the maximum tension placed on the shock linkages.  Add a suitable safety factor and design the linkage accordingly.  Use 2024 T3, it's free machining.

Once you have a design making it is simple.  You will need: 

1) set of straight dividers
1) 12" machinist's rule
1) bottle layout dye
1) center punch
1) scriber
1) piece of plate large enough to make your parts plus a few mistakes
1) bandsaw with a suitable width 12 pitch blade set at 350 or so FPM.  Faster with coolant.
1) drill press
1) drill bit of the necessary size
1) #30 or thereabouts pilot drill
1) hand reamer for the final diameter
1) smooth cut mill file

How:

Lay out your dogbone on the plate using the dividers, rule, scriber and layout fluid.  Mark the centers of the two holes with the center punch.  Cut this out as a rectangle leaving plenty of material around your scribe lines.  Rough out a two more pieces of plate the same size and clamp to the first.  Match drill the holes on a drill press, remove the clamps, deburr, ream, and clamp two together with a couple shoulder bolts sized to fit the holes with a hand press fit.

Take the third piece and clearance drill for the bolt head.  This sacrificial plate will allow you to match cut on the bandsaw without the bolt heads contacting the table.  Match cut your two dogbones on the bandsaw and deburr.

Optional:  Sand quickly with a jitterbug at 600 grit, then polish to a mirror finish.   

CNC is a waste of resources for a part so simple.  In fact, with a little practice on a bandsaw you could make them faster by doing 10 at a time. 

No bandsaw available?  Go down to the hardware store and buy a hacksaw and a bastard cut 12" mill file.  These replace the bandsaw.   

[Alphamazing]

I think I'm gonna get some bar stock and get it cut to length, and then have someone with a drill press drill the holes where I need them. I'll do the finishing work on my own.

[GeeP]

Make sure to match drill the holes.

[Alphamazing]

Make sure to match drill the holes.

Well yeah. Clamp the two pieces together and drill. Not too difficult! Thankfully I can get some really ugly lookin' dogbones made easy. They don't need to be fancy or anything at all, just a bar of steel with holes. A simple mechanical design that works great; sounds like a dream come true.