The main clue to whether you may need to replace your fork bearings is a shudder while braking from higher speeds. This may also be caused by the front brake shoes or an ovaled hub, but a distinct shudder is usually due to the fork bearings failing, or at least the securing nuts may be loose. Either way here's how to remove and replace the fork bearings.

The first step is to remove the headset top and headlight to get to the fork tube pinch bolt. Unlike Vespa, Lambrettas have the pinch bolt inside the headset with no access from the outside. Unscrew the four small screws that hold the chrome hexagonal ring to the headset top and bottom. The headlight can then be removed if you want it totally out of the way, or just remove the upper two and loosen the lower two which will give the ring enough play to get the headset top off. The bike shown here is an Li125 Special Series III (similar bodywork to a TV175 and SX150). If you have an Li you will need to remove the three screws around the headlight chrome ring instead.

The next step is to remove the headset top and disconnect the speedo. Remove the two screws (one on each side) from the underside of the headset to allow the top to be removed. The speedo cable will hold the headset top down - don't try and pry it up! Locate the point where the speedo cable is connected to the front wheel, and feed it upwards as much as possible. This should allow the clearance needed to lift the headset top, reach in, and unscrew the speedometer cable from the speedo unit as well as pull out the single speedo bulb. The headset top should now lift off.

You can either move all the wiring to one side, or disconnect it all from the headlight block. Make sure you keep a good record of where it all plugs in for the rebuild. Once everything is out of the way, you'll see the single Allen head pinch bolt which keeps the headset connected to the fork tube. Loosen and fully remove the Allen head bolt and shake proof washer.

Since the brake cable on a Lambretta does not run through the forks you can simply unscrew the large circular adjuster (arrowed).

Once the adjuster is removed, push the threaded part back through the arm, and disconnect the brake cable from the casting in the brake hub.

Grab the levers of the handlebars and twist from side to side while holding the front wheel in between your feet. As you do this, lift up and the headset should start to rise up and off the fork tube. Most bike will have enough length in the electrical and control cables to allow you to get the headset off the tube and fold it back without disconnecting anything.

If you have the correct tool for this job it is by far the best way to loosen the retainer. I don't have one so I use a flat head screwdriver and hammer to loosen the top retainer. It unscrews just like a normal nut.

After the first retainer, there is a single washer with a small peg which slots down a groove in the fork tube. Remove it and check the peg is in good condition. If not, replace the washer.

The final retainer can be removed with a large wrench. Make sure the front wheel is supported if your center stand lifts it off the ground. It is harder to loosen this nut with gravity pulling the forks down.

As the last retainer comes off, the caged bearing is visible in its groove. Once the retainer and bearing race are out of the way the forks can be dropped out of the bottom of the bike, along with the speedo cable.

To drop the forks, place blocks under the center stand to get the front end high off the ground. You can also remove the rear shock to drop the rear of the bike even further. As the forks drop out another larger bearing race will be visible under the front mudguard.

I happened to have my front wheel off in the shot above, but it is not necessary if you are just removing the forks. This shot was also before the blocks under the center stand to get the forks clear of the bike.

With the forks out of the bike, you can either rebuild them, repack the old bearings with grease, or replace the bearings completely. Inspect the surfaces that the bearings run in and clean them up with a solvent to remove the old grease, and steel wool to remove any surface rust. If the bearing races are pitted or badly rusted they should be replaced (you'll have to look in the service manuals for how to do it as this bike didn't need them replaced).

When reassembling the forks into the frame, make sure all the bearings are well greased. Always use the both retaining nuts with the pegged washer in between. This effectively makes a locked nut system so that it cannot loosen while you are riding. When tightening the first retainer with a wrench make it tight enough so the forks can't rock about, but loose enough so that when the wheel is off the ground, the forks will fall to the left or right from center if given a little tap on the front wheel. Make sure you use a shake proof washer when reinstalling the pinch bolt. Before the headlight is installed do your best to make the headset point straight when the front wheel points straight. Tighten the pinch bolt and quick test drive will let you know if you are aligned before reinstalling the headlight & headset top. If not you can easily make small adjustments by loosening, but not removing the pinch bolt.