Moto Guzzi V700, V7 Special, Ambassador, 850 GT, Eldorado, 850 California - Shocks

Shocks - Koni / Ikon rear shock rebuild

Updated: 2008 Jan 15

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NOTE: Koni / Ikon rear shocks were NOT used originally. However, they are a common replacement shock that performs very well.

One of the benefits of Koni / Ikon rear shocks is that they are infinitely rebuildable. Here's how:

• Get a rebuild kit from Proven Suspension in Australia.
• Refill each with 85ml of 5 weight fork oil.

Shocks - Koni / Ikon spring selection

Updated: 2008 Jan 15

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NOTE: Koni / Ikon rear shocks were NOT used originally. However, they are a common replacement shock that performs very well.

I extracted this information from Mike Tiberio on the Yahoo! Loopframe_Guzzi news group. In Mike's own words:

Got a set of long lemans IV konis off ebay, but was not happy with the soft spring. Had to run the preload up one notch to prevent bottoming, which ruined the ride. Had mg cycle order a #204 spring from australia. $110 later, the eldo rides like it should. Floats over small bumps, and doesn't buck over the big bumps. The spring is now working the progressive part of the rate properly. just my $0.02 to add to the collective knowledge base…

Question posed by Gregory Bender: Do you know what the original spring rate was? Or rather, how did you know to go with #204 springs versus another number?

Are you asking how did I know what direction to go on the spring rate? I doubt that's what your asking, but its an easy answer. 1) the spring that comes on a Lemans would by design be softer than one usually fitted to a heavier touring machine, so I guessed I had to go stiffer. 2) The spring from the Lemans IV was the softest IKON/KONI made for the longer 7610-1429 shock. Since I was able to identify that my ride suffered due to bottoming, and not non-compliance, I knew I had to go stiffer, and it was the only alternative spring anyway.

How did I know not to got 2 steps higher to the #217 spring? I didn't, and might yet if I felt I had to. Sometimes (as you well know) you have to gamble with $110. I don't wager on sports or cards, so wagering on something I could sell on eBay is no biggie…

Note the springs numbers are not rates. They make no sense:

• #230 is at 84-146 pounds/inch progressive
• #204 is at 100-185
• #217 is at 123-218

Whats even loopier (no pun) about the koni/ikon springs and shocks is the short shocks (stock for short swing arm guzzis like loops) numbered 7610-1297 have 255 mm long springs, the longer shocks have 235 mm springs???

So if I want to have alternative springs for my Vert which runs the standard 7610-1297 shock, I can't use the ones for the 7610-1429!!!

One last note on the shock geometry between loops and early tontis. Both have short swing arms, that are the same length from swing arm pivot to rear axle. Yet I noticed a decided difference on how each rode on the same KONI recommended shock. The only shock geometry difference that I can see is the upper shock mount on the loop looks to be further back than on the tonti. This would make the loop ride stiffer that the tonti given the same shock. That's what I saw, and that's why the 1297 that I originally bought for my loop is on the vert where it works fine, and not on the back of the loop where it beat the sh*t out of me. I do have a firm solo saddle, so all my "suspension" is in the shocks. Last point, I think the two bikes are about the same in weight, the vert has all the hydraulic stuff, but a lighter frame and fenders. If the loop is heavier, it should have ridden better on the stiff shocks, it didn't, and I doubt being lighter than the vert is why it rode stiffer…

Shocks - Tear down and rebuild of the stock shock step 1: outer

Updated: 2008 Jan 15

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The following procedure is applicable to the commonly fitted original equipment rear shocks.

I extracted this information from Ray Hale on the Yahoo! Loopframe_Guzzi news group. In Ray's own words:

1. Shock spring compressor from MG Cycle. I cut the notch on the bottom piece about twice as wide so it would fit over the big Guzzi spring. The tear down is an easy one-man job if you put the compressor in a vise. The top piece pulls downward to compress the spring when the shock is in place.

   

2. The top end of the shock fits into the hinged end of the compressor, using this pin through the hole in the upper shock mount. Leave the old grommets intact for a better fit.

   

3. Fit the bottom of the shock spring into the widened slot on the bottom arm of the compressor. Pull down on the top compressor arm, compressing the spring, and twist the lower shock adjusting collar. You might tap with a mallet to loosen.

   

4. While twisting, when you line up the slot in the adjustment collar with the tab on the shock body, the collar will slip off the bottom end of the shock. This is done by feel, turn and pull, although you can see in the bottom of the collar with a flashlight.

   

5. Next comes the bottom cup. It also might need help with the 'tapulator' and a little loose-juice. Remember these parts are getting hard to find. Don't rush and ruin what you have.

   

6. Now the spring is free to come off the shock body. Release the compressor top handle and lift the spring out of the tool. Don't be too disheartened by its appearance. Mine cleaned up pretty damn nice.

   

7. Pull the upper cup down and off. These also cleaned up real well but I may have them chromed. Shiny stuff against gloss black! Oh ya!

   

8. The plastic tube is a bit of a challenge. It has to clear two tabs on the shock body. Gently squeezing it will distort it and allow passage. Down and off. Maybe twisting some on the way. It'd be fairly easy to rip them if you're not careful. Put on some tunes. Music helps! For me it was vintage Frank Marino.

   

9. Pull the pin at the top of the compressor and the shock body comes out of the tool.

   

10. Shock body as far as I could figure out how to disassemble. Anyone know if this can be taken apart further and re-oiled? If so, please post to the looplist or to me at ray.hale>at<sfcc.edu.

    

11. All the parts on the left. Complete shock on right.

    

12. Adjustment collars. They clean up nicely with some grunt and groan. I am trying some stuff from Eastwood called Nyalic clear coat in an attempt to preserve the polish.

    

13. These are the cups, before and after cleaning. I had two sets. One was pretty bunged up from what looks like tool misuse.

    

14. Finished! Ended up having the metal parts rechromed. Painted the black stuff gloss. Got new rubber bushings from MG. Purtee…

    

Shocks - Tear down and rebuild of the stock shock step 2: inner

Updated: 2008 Jan 15

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The following procedure is applicable to the commonly fitted original equipment rear shocks.

I extracted this information from Rob Prins on the Yahoo! Loopframe_Guzzi news group. In Rob's own words:

No one should accept responsibility for the accuracy of this document since I wrote it myself and I could be wrong.

1. Main parts are (my names): outer tube, inner (pressure) tube, rod, seal nut, orifice assembly #1, orifice assembly #2
   
   The seal nut must be removed using a pin wrench, I used a bicycle tool I have in my stock, but I may build something custom for future use.

   

2. After the seal nut is backed out of the outer tube, the inner assembly can be removed; here is what she looks like.
   
   These parts, (left to right: orifice assembly #2, inner tube, orifice assembly #1) are not attached to each other. I think they are pushed together by the seal nut when installed, but they easily fall apart in disassembly

   

3. Orifice assembly #2 basically falls off of the inner tube

   

4. From right to left, the rod assembly including seal nut and orifice assembly #1, the inner tube, and orifice assembly #2 (disassembled).
   
   As the shock extends and compresses as with normal driving, orifice assembly #1 is forced up and down in the oil that is in the inner tube.
   
   Since you can't really compress the volume of oil, it has to go somewhere, in this case it is forced to flow through the orifice assemblies.
   
   Flow resistance is related to orifice size, oil viscosity, and oil speed. As you might expect, resistance increases as either the orifice size is decreased, the viscosity is increased, or the velocity is increased.

   

5. Orifice assembly #2 has 3 basic parts; the orifice plate (center) and two thin disks on either side that act as reed valves. The remaining hardware clamps the 3 basic parts together. The orifice plate has 6 holes, the center hole is for the clamping bolt, the remaining 5 holes are for oil to pass through.
   
   As the shock is compressed, oil is forced against the disk plate shown on the right. The disk plate acts as a reed valve and closes off the 4 rectangular holes, but the "C" shaped slot allows the oil to go through the small hole that is positioned at roughly 4 o'clock relative to the clamp hole. Apparently oil goes through this hole with significant force since the small disk (shown on the left) is bent; both shocks I took apart showed this effect.

   

6. Orifice assembly #1 is mounted to the rod and has more parts than orifice assembly #2 (not all of them are shown in the picture) but the operation is basically the same.
   
   The different orifice sizes and the "reed valves" are (presumably) the result of the original designer specifying different damping ratios for compression and rebound.

   

7. There are 4 rubber parts in the assembly, one of which is visible without disassembly. My names for the parts are: exterior jounce bumper, interior jounce bumper, rod seal, and pressure tube top seal. All of them were in decent shape in my case, which is good because I have no idea where to get new ones.

   

What I did was:

• Clean all the (non-rubber) parts with mineral spirits
• Replace oil with SAE 30 (this may prove to be too stiff)
• I attempted to measure how much oil was in the shock when I disassembled it. However, before I took them apart I noticed a "dead-band" on rebound where after compressing the shock I could rebound it without much resistance for a short distance - not enough oil in the pressure tube? I filled the shock on reassembly; as I turned the seal nut back into the outer tube the extra oil was forced past the threads so it self-leveled.

What could be done:

• You could "tune" the parts by changing hole sizes etc but if you want real tune-ability you should pony up and get Ikons. A better approach for the budget minded would be to tune with viscosity, find one you like and stick with it.
• I didn't do anything special to seal the threads on the seal nut. This may be a problem, but I'm not convinced it will be since the oil is only pressurized when it is in the inner pressure tube.
• I may yet attempt to measure the damping ratio of an original unit and compare it to rebuilt units containing different viscosity oils. I think I can do this by applying a load (like a dumbbell) and seeing how long it takes the load to extend or compress the shock. I guess I could get denser data by testing with various loads. If I get carried away I could test my Ikons the same way for each dial setting as a comparison.