Jet Set Scooterlab
Rebuilding a Front GS160/SS180 Shock
The front shock unit on the GS and SS is unique to these models, and are hard to find. There are aftermarket shocks made but are reportedly of questionable quality. Here is how I rebuilt an original shock by dissassembling it, powdercoating it, and rebuilding it with fresh heavier-weight shock oil.
- Dissassembly.
- At the top of the shock there should be a nut and possibly a washer. Remove this.
- Then comes the potentially hard part. You will need to remove the top of the shock by screwing the mounting bolt pin down through it. These can be rusted solid - try some penetrating oil. Hold the top of the shock in a bench vise and use a flat head screwdriver to screw the pin into the shock (clockwise). You'll need a screwdriver with a narrow enough head to fit inside the hole once it goes that far. Remove the top.
- There is a rubber buffer inside the top of the shock. Remove it if you are going to powdercoat.
- Remove the spring. You can get up-rated or even progressive springs for these shocks from some German shops - try Stoffis or SIP. I re-used the original.
- Removing the seal.
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- At the top of the bottom half of the shock there is a seal plate with two 4mm holes and a larger hole that the pin goes trough. This unscrews wih a special tool, but I used some vise-grips and an allen wrench to improvise. Hold the shock bottom in a bench vise. Use a 3.5 mm allen wrench (for you Lambretta mechanics) or a 3mm works fine, or try a 4mm bolt. Clamp it tightly in the vise grips so the grips surround the pin and the allen wrinch end fits into one of the 4mm holes. Carefully unscrew counter-clockwise and remove the seal plate. It should be tight unless you've got a leaky shock.
- Under this may be a flat seal, or maybe not. I've seen two different seal arrangements in these. There is one kind that has the seal built onto the piston assembly, and another with a seperate flat seal.
- Remove the piston assembly by pulling out the pin. Careful as it is in a bath of shock oil. Let it drain into the shock as you lift.
- Pour out the remaining shock oil.
- Paint/powdercoat.
- If you want to paint or powercoat the shock clean it carefully, tape off the oil chamber (and threads). If you are powdercoating, remove the rubber bushing with a vise and an appropriately-sized socket. Just mask it off if you're painting.
- Reassembly.
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- Pour in new oil. According to the GS160 workshop manual, the front shock should contain 49/51 cm3 of Esso Univis J43. I used heavier weight shock oil which should provide better damping and less dive while braking. Ask your Motorcycle shop for advice.
- If you have a leaky shock you will need to get a new seal, and probably had too little oil in it when you took it apart.
- Carefully lower the piston assembly into the oil.
- Replace the seal. My seals were fine, so if you need a new seal you're on your own. There are folks on the vespa sports email list who may have a lead on these, but again there are at least two types of seals.
- Replace the plate using the vise grip tool. Tighten pretty tight. (Hows that for science)
- Replace spring, making sure it is grit free and nicely greased.
- Replace rubber buffer.
- Screw on shock top.
- Replace nut and washer. There should be about 1 1/4" of the threaded pin showing at the top.
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