1970-1973 XS1 XS2 rear shock absorbers, stock and aftermarket, comparison, compatibility, performance, and musings

DogBunny

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An aftermarket Taiwan XS1B shock, original 1970-1971 shocks (with blue spray-paint), and original 1972-1973 shocks.

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First, let's dispense with the Taiwan aftermarket shocks.
Here's the current cheapest link:
https://www.ebay.com/itm/152151308883
or:
http://www.nichecycle.com/ncs/categories/suspension/shocks/17-06710-xs1b-shocks-by-ncs.html
Currently about $74 total shipped to your door.

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They are junk. Very cheap components. They aren't even engineered correctly. With the bottom adjuster set at the stiffest (highest) setting, the bottom shroud will get crushed after the damper compresses about half-way, and/or damper travel will be impeded.
They are very pretty shocks. They're only usefulness, in my opinion, is to put on a bike that you are intending to sell. Let the new owner deal with the poor performance. If you intend to use a pair for yourself, I would at least cut the bottom shroud down so that you don't risk the crushing issue and restore full damper travel.

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The Taiwan shock is significantly less robust than stock, and has less damper travel. The spring (previous pic) is also a lot cheesier than stock.

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The stock and the aftermarket shrouds are the same outside diameter. So, if your stock 1970-1971 shrouds are poor, the Taiwan shrouds can be made to work, with a little modification. First, you will want to cut down the chrome lower shroud as previously pointed out.

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The shaft hole in the Taiwan shroud is smaller than stock, so it will need to be enlarged. Also, note that there is no inner lip (arrow) on the aftermarket shroud. That lip strengthens the stock shroud, and keeps the spring centered. Another example of the aftermarket shock's jankiness.

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Aftermarket (left and stock top eyes, showing why the hole diameters in the previous pic are different. Note that the stock eye is more robust.

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The shaft hole in the Taiwan bottom shroud is a lot bigger than it needs to be, and once again, does not have the strengthening inner lip that will keep the spring centered...

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...resulting in a very sloppy fit.

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So really, what were you expecting for $70? The aftermarket XS1B shock has been cobbled together from existing cheap shock parts. And a pretty candy orange shroud has been added. If you search through eBay or AliExpress, you will find several examples of $70 shocks using the same components. Intended for bikes in the 125 to 250cc range. The example above, is even "Hign" Quality!

More to come, including a look at the 1970-1971 stock shrouded shocks compared to the 1972-1973 unshrouded shocks.
 
Before proceeding, let's back up for a moment and take a look at disassembling shock absorbers, which requires a spring compressor tool.
Fully shrouded shocks require a special tool, that you will have to make. Here are a couple of examples.
https://www.xs650.com/threads/mk-1-shock-spring-compressor.62488/
https://www.xs650.com/threads/xs2-rear-shocks.26835/
And a really good example here:
https://www.xs650.com/threads/were-off-to-see-the-wizard.61487/page-6#post-737931
And more discussion here:
https://www.xs650.com/threads/who-is-still-running-their-original-xs1-shocks.66690/

There are off the shelf spring compressor tools that you can buy for unshrouded or partially shrouded shocks. I didn't have one, and couldn't wait for one to arrive, so with a lot of fumbling around, I finally got a ratchet strap to work. (that's 2M's fully shrouded spring compressor tool at the top of the first pic, currently on indefinite loan to me.)

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Disassembled 1972-1973 shock (top) and 1970-1971 shock.
The dampers are outwardly identical. The adjusters are the same. The rubber top-out limit donuts are slightly different.
Spring length is the same. Spring wire diameter is the same. However the spring outer diameters are different. The 1970-1971 spring outer diameter is 48mm, while the 1972-1973 is 52mm. I have to presume that the larger spring is an engineering Improvement. The larger diameter spring WILL fit into stock or aftermarket 1970-1971 shrouds.

So, given a choice, if I was cobbling together a set of 1970-1971 shocks from various parts, I would use the larger diameter 1972-1973 springs. I would also use the 1972-1973 lower dampers, just in case they are also an improved design with better internals.
Assuming the dampers are still good. With the shock upright and spring removed, push down on the damper rod. There should be resistance. If the rod pushes in easily, the shock is no good (and these dampers are not rebuildable). Pull the rod back out. There should be at least as much resistance as you felt pushing in.
 
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Damper rods from the shrouded units I've seen always seem to be near perfect condition.
The exposed rod XS2 type units I've looked at have had terminal rust pitting of the rods, with the damping oil long departed.
Another brilliant styling trend copied from the British motorcycle industry.
Apparently done to aid air cooling of the dampers in competition conditions.
 
On most of the stock shocks I've checked, the damping is bad. The compression damping may be OK but usually the rebound damping is shot. When you pull the rod out, the damping "skips". You'll get areas of resistance and areas of no resistance at all. I've often thought that maybe changing the oil may help. Oil being so scarce in Japan, I heard they put fish oil in these old shocks (forks too), and it doesn't last long. One would need to determine a spot to drill and tap a drain/fill hole. To do that, I think a bad shock (rusty rod, leaking) would need to be cut open. Then you could locate a suitable spot that's thick enough for the drain/fill screw. There would also need to be clearance on the inside so the screw doesn't hit or impede the internal damper parts.
 
The 1970-1971 shocks in my comparison are shot. No dampening resistance and no rebounding resistance.
The 1972-1973 shocks are good. Good resistance dampening, and even more resistance rebounding.

The aftermarket shocks have considerably less resistance in both directions then the 1972-1973 shocks. Yet another reason not to recommend them. They are evidently adapted from shocks designed for lighter bikes.

Will mention that I don't have a real lot of experience messing with shocks. These are the first ones I've disassembled. But, I think it is normal for a shock to have more rebound resistance then compression resistance.
 
Yes, that's probably true, but I don't think the rebound damping should have those "blank" spots in it, sections with no damping at all.

I've been taking shocks apart for years, mostly for clean-up but sometimes to rebuild (Konis). Also to use the springs on other shocks. Stock BMW shocks were better than most Jap shocks but eventually did wear out. But the springs were very good. I've used them on several sets of aftermarket shocks over the years. In fact, the older 76 series of Koni shocks often didn't come with springs and you were supposed to use your originals.
 
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I don't think the rebound damping should have those "blank" spots in it
Definitely.

Will reiterate that testing should be done with the shock in the upright position, so that all of the oil is in the bottom. Otherwise, you are just pushing air through the bottom disc passages.

I agree that rusty/pitted shafts are bad. However my 1970-1971 shocks are completely shot, and the shafts look just fine.
 
I have a couple very nice fittings I made for my hydraulic press, one for open springs and one for covered springs .....

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They work very well but I wanted something a bit more portable, so I made a bench top lever type based on this one I saw online .....

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It works very well. I haven't made a fitting for covered shocks yet but I will eventually.
 
I have this tool and I’ve disassembled stock Special shocks with it. I strongly suspect it would be suitable for early XS shocks as well.

https://www.progressivesuspension.com/product/1477/shock-tool-for-psi-shocks

This if you would prefer to buy it rather than make one.

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I like that tool, and will probably eventually buy it. However, I am skeptical that it will work on the early shocks.
Here are the instructions:
https://www.progressivesuspension.com/assets/files/PDF-Vtwin/shocks/3055-129-Instr-Shock-Tool.pdf
In step 4, figure 2, a retaining clip is removed. The early shocks don't have a retaining clip, they have a nut that has to be unscrewed. It's a big nut, 26mm. I don't think there is room to get a 26mm wrench into the tool, but I could be wrong.
 

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Thats a relative bargain for that tool. I'll probably order one too, but I hate to buy from that guy...he's kind of a smart ass prick.

I dealt with him on a gas tank for a KTM 300 and his customer service skills are shall we say "severely lacking". :mad:
Lots of vendors sell it. Here's the cheapest one on eBay:
https://www.ebay.com/itm/126815326307
With tax and shipping, the eBay one above is a few cents cheaper.
 
Thats a relative bargain for that tool. I'll probably order one too, but I hate to buy from that guy...he's kind of a smart ass prick.

I dealt with him on a gas tank for a KTM 300 and his customer service skills are shall we say "severely lacking". :mad:
Lots of vendors sell it. Here's the cheapest one on eBay:
https://www.ebay.com/itm/126815326307
With tax and shipping, the eBay one above is a few cents cheaper.
I've got plans, drawings and ideas for a homemade compressor loaded on the computer. For more years than I'd care to admit, I've planned on building my own. Since I turned 70 a few months ago, I've had a revelation of sorts... pick your battles. I'm sure I could make a nice one.... that would involve several hours if not days building and then tweaking.... vs the 30 bucks shipped I paid for this one. Yeah, pick your battles. :whistle:
 
I for some reason didn’t pay shipping or maybe that was offset by a $5 coupon I found somewhere :). Don’t know the business but needed a tool ( the one I could borrow from the advanced auto part was to big to fit between the spring coil, figured it was worth a shot - as mentioned it was easy to use and worked fine for it purpose.
 
I've got plans, drawings and ideas for a homemade compressor loaded on the computer. For more years than I'd care to admit, I've planned on building my own. Since I turned 70 a few months ago, I've had a revelation of sorts... pick your battles. I'm sure I could make a nice one.... that would involve several hours if not days building and then tweaking.... vs the 30 bucks shipped I paid for this one. Yeah, pick your battles. :whistle:
Yeah, the "picking your battles" reality sucks. I have slowly and grudgingly started to farm out things that I could better do myself, but don't have enough time remaining...
 
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