More about shocks (dampers, really)

[SP3]

I've been fooling with shocks for my Monza (and many many other bikes) for about 15 years, on and off. While helping another member sort his out, I now know of four different types regarding shaft size and seal retention.

My Monza's originals have 9x22x7 seals. The seal is pressed in, a steel plate over the seal, and that is held by the lip of the holder being peened over.

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I have a number of spare sets with 10mm shaft and 10x22x7 seals. These are also pressed in. But, there's no steel plate. The holder (slightly different design to the former) peened over.

IMG_4446.JPG

The member I'm helping has dampers with 10mm shafts but the seal OD is 24mm. I don't yet know how they are retained.


While going through all of this, I just happened to notice ONE seal holder very similar to my spares externally. But, it has a plate, like the originals. The plate, however, in far thinner, has a hex for the through hole, and it threads into the body to keep the seal in place.

I would guess that the screw-in type came before the no-plate type. A neat idea but, the bean counters said that it cost too much to stay with and they went to press-in. Just a guess.

IMG_4447.JPG

IMG_4448.JPG

I (mostly) subscribe to the 'nobody is as smart as everybody' line of thought. So, can anyone/you all lay out a timeline for changes in these dampers and maybe what models they were used on most? It's not critical, obviously. You can't really see the difference when together and on the bike. Just like to know a bit more.

Internal differences can be another thread someday.

[Rick]

That hex drive threaded retainer is nice- could probably use a bolt head to install it- It's good to see part variations, hope someone can help place them in model or year order.
Rick

[KarstenH]

Hello,

on my early Diana from 62 i have found the same dampers with the hexagon plate.

[DucRedux]

Completing the disassembly of one shock this afternoon, I noticed that the cylinder had a hex head as explained above. The inset seal seems to be about 10 mm ID for the shaft, 28 mm OD and maybe 7+ mm height. After looking at this site below a few minutes ago, my hope for a reasonable rebuild is heightened. Is anyone familiar with other sources?

http://crcseals.com/MetricProducts/Symm ... Seals.aspx

[SP3]

your link brings up a U seal. you need a single lip seal. they are usually called oil seals. post a photo or two of the parts/seal.

[Nick]

When I rebuilt the shocks on my Sebring I used a water pump seal from a Suzuki, but that was about 20 years ago.....

Edit: Think I had to machine the holders to accept the seals. Used ATF for shock oil. Still riding the bike and no leaks, so they're working well.

Before the rebuild there was zero rebound damping because all the oil had leaked out. When exiting or entering bumpy turns this would cause the rear tire to slide. The slides were small and controllable, but it was a good practical lesson in the effects and benefits of rebound damping.

[amartina75]

The shocks on my 66 scrambler are the hex threaded type. If this post had been around when I rebuilt them a couple years ago I probably wouldn't have ruined one of the caps trying to get them apart. I was unaware that any of them were threaded in. I thought they were just staked in place like the round hole ones. The threaded caps would be the earlier design. The seals used in that type are inferior to the later seals. They are not a true oil seal, and can't be replaced with any modern seal I know of due to the weird shape. My brother machined the caps on mine to accept a standard oil seal that I was able to buy at a local shop. That is what I would recommend doing for anyone with that type of shocks.
Aaron

[SP3]

My oddball holder didn't have a seal in it so I don't know what it looks like. I am picturing valve stem seal with the spring seat as one part but, made 'upside down'. like this:

[amartina75]

My oddball holder didn't have a seal in it so I don't know what it looks like. I am picturing valve stem seal with the spring seat as one part but, made 'upside down

basically, yes you are right, but I don't think it had a spring, maybe it did i can't remember it was some time ago. Either way it is only a single lip seal.
If you machine the caps for new seals you can use a double lip seal.
maybe someone currently working on theirs can post a picture of the seal

[SP3]

Single lip with a spring has worked for me. Of course, a lot will depend on how loose fitting the shaft is though the holder's guide. I've thought of machining a pair and installing bronze bushings, reamed to fit. A seal can only compensate for so much movement.