Tech Torque: Lambretta gear selector overhaul

On the Lambretta gear selector system, there are several areas where wear can occur, sometimes making it difficult to operate. Stu looks at how we can fix these issues…

series of splines and uses a pinch bolt to secure it. This needs to be fully tightened, but it is difficult to gain access to it. Because it can come loose easily, periodic checking is advisable.

To gain full access it is easier to take the rear wheel off. This is probably why Innocenti changed to a fixed type. However, if you replace the 6mm thread pinch bolt to one with an Allen key head, it is possible to tighten it up much easier. Make sure if you do the replacement bolt is long enough to go through the entire length of the thread to avoid it stripping when it is fully tightened.

Now concentrate on the end that is connected to the tie bar, which is the same for both types, fixed or two-piece. Not only does the hole on the tie bar wear and elongate, but over time the fixing point on the gear shaft does as it is only 6mm wide. Replacing the tie bar is easy enough, as is the top on a two-piece shaft. However, the fixed GP type requires the whole transmission to be removed if it needs replacing. A solution to this is to replace the worn part on the top with a stud. The benefit of this is that not only is it replaceable without stripping the transmission down, but also it does away with the awkward little circlip that holds the tie bar in place. Instead use a 6mm nyloc nut to hold it in position, making it far more secure and much easier to remove when required. Start off by cutting the top off where the tie bar locates on to it and filling the surface flat. Drill a hole straight through it 5.5mm wide, then using a 6mm tap, cut a thread into it. The stud needs to have a thread on top, but be clear where the tie bar sits. The best one to use is what is fitted into the casing to hold the rear wheel end plate bearing in. This has a long enough thread to go into the gear shaft with enough clearance for the tie bar to sit anda long enough thread to wind a 6mm nyloc nut on to it. Always fit a washer under the nyloc nut and tighten so there is a 1mm gap between it and the tie bar to give enough free movement. Not only is it easier to undo rather than try to remove the small circlip it is replacing, but also if the stud does wear over time it is simple to change.

Quite often an overlooked are where play in the linkage can occur is with the bush that holds the gear shaft in position. This is made from brass and is around 20mm in length. Though you wouldn’t think it, once worn it can exaggerate the play on the linkage quite considerably. Changing it is quite easy, only requiring it to be drifted out and a new one tapped back into position. The only problem is that the gearbox will have to be stripped to do so. It’s always worth remembering if

Right: Always check there is enough clearance for the pivot to move over the number stamp area on the casing. If it is to close this issue can be solved by fitting a small shim underneath the top piece of the pivot

Above: With the correct length trunnion in position it will fit all the way to the bottom of the pivot, and clearly shows the hole for the gear cable is clear.

Above: If the shorter length trunnion is fitted on this side of the pivot it doesn’t sit in the bottom correctly and will wear the top half pretty quickly