LAMBRETTA GEAR SELECTOR OVERHAUL

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

When Innocenti designed the Lambretta, its styling was compact and enclosed. Part of the process was to position the gear change system on the handlebars. Though, in theory, this made changing gear easier than the traditional foot control method, it did create its own set of problems. Most of these issues stem from the fact that there are far more linkage points, which can all suffer from wear. By the time you actually get to the gear selector in the engine, this ‘loose play’ can have been greatly exaggerated, the result being severe play on the handlebar control itself. Even if the gear cables themselves are in perfect condition, each part of the system needs to be checked and overhauled where necessary.

Handlebars

Working along the chain of linkage points, it starts with the handlebar gear change. The first place to look is where the rod end goes into the gear changer housing. Up until later series three models, this was a thin fixed end, which fits into a narrow slot on the housing. Problems arise from wear to the slot on the housing. The only real solution to repair it is by welding it up and creating a new profiled slot. This isn't easy as the steel is thin and will need grinding out. If you do attempt this repair, the slot must go back into its original position, otherwise the gear numbers will be out of position and by aligning them the clutch lever would then be out of its natural position. To make sure it is in line, scribe a mark along the length of the steel level with the slot so you know where to cut a new one afterwards. It has been known for the rod and housing to be welded together. The problem with doing this means that if you need to remove the rod for any reason, then the clutch cable will also have to be removed as it has now become one piece,

so this repair isn't practical. On the later series three models, this system was done away with and replaced by a nylon end that sits in a much wider slot.

The nylon end wears over time around the split pin that holds it in place, causing play. This can easily be changed for a new one, but always replace the split pin as well, as that can become worn where it goes through the rod.

The other end of the rod holds the cable pully in position. The earlier slot type uses

a brass wheel, which is held in place on a series of splines on the rod itself. This is secured in position by a pinch bolt and wear is virtually unheard of. The pinch bolt can come slightly loose so may need tightening up. Take great care if doing so as the bolt can easily snap in the pulley and it is almost impossible to extract, meaning you will require a new one. On later models that use the nylon pulley system, it uses the same method of locating by a split pin. Again over time,

this can become slack where the nylon has become worn. Replacing the pulley is the only option, and again replace the split pin at the same time. Whichever type of rod and pully your Lambretta has fitted, once you know everything in the headset is in perfect condition you can then move on to the next point, which is the pivot control on top of the engine casing.

Pivot control

The pivot control on top of the engine casing is made up of two separate parts, but also has the tie bar and cable trunnions connected to it. Starting off with the pivot itself, both the piece that bolts directly to the casing or the opposing part that sits on top can be worn, giving excessive play. It is possible to get the top piece sleeved for a better fit when worn. If not, then directly replace it. Always make sure when changing the pivot base that it is bolted on the right way round. If it isn’t then it is not possible to select all the gears as there isn’t enough travel on the swivel part that sits on top. Remember when bolting the base to the casing that it sticks out over the edge. Though this may look odd it is correct, and often confuses when the side case has been removed. Remember when the side case is fitted the leading edge of the base doesn’t stick out. Once happy that both are free from wear you can move on to the trunnions.

The cable trunnions were originally made from brass, but in later years have been replaced by ones made from steel. The problem with the brass-made ones is that they are prone to wear because the metal is softer. The biggest problem is the one connected to the tie bar as over time a groove can get cut into it, greatly exaggerating any play. Today most are made from stainless steel and are much harder wearing. Take care when replacing the trunnions and always make sure you change both, checking that they both have the same size Allen key grub screw. This is because originally the size for the Allen key was 3.5mm and on newer ones is 3mm. You wouldn't want to change a snapped gear cable out on the road and find out you have odd sizes and only one key that doesn’t fit both of them.

The next important thing is to make sure that the correct trunnion is used on each side of the pivot. On the left-hand side, the trunnion is much longer as it has to allow the tie bar to go through it. If you use the shorter one then it is not long enough to go through the bottom of the pivot. Likewise, if the long one is used on the right-hand side it is too long and will be exposed underneath, and can catch on top of the casing. Also be aware if you have changed the pivot for an aftermarket one, as sometimes these can sit slightly lower. If it does, then it is possible for the trunnion or pivot to catch on the casing on or around the raised engine number area. If so, then it is possible to sit a shim underneath the top piece of the pivot to raise it slightly and avoid the situation from occurring. Finally, on the pivot is the one end of the tie bar that has the trunnion running through it. This end can get worn or elongated, and if so will need replacing, even though it is the other end that usually wears first. Just like the headset, once this section is checked and repaired where necessary, move on to the next one.

Gear selector arm and shaft

The gear selector and shaft are what go into the casing and connect to the wishbone. There are two types, a twopiece or the later GP fixed one-piece version. The two-piece has two problem points. Firstly where the other end of the tie bar connects to it, which can wear. Secondly, where it bolts to the shaft, this can come loose quite easily. As the first part affects both the two-piece and fixed-piece arm, we will look at where the two-piece one bolts first. It sits in position on the top of the gear shaft by means of a

This fixed type gear changer rod was used from series one right up until later series three models.

Above Right: Later series three models used the nylon end to sit in the gear changer body, but it is prone to excessive wear over time, althoguh it is easy to replace.

Above Left: On the other end sits the brass gear pulley, which is held in location by a series of splines. Great care should be taken when tightening the pinch bolt as it is easy to overtighten and snap it off.

Above right: The pivot base here is bolted the wrong way round and will not allow full movement of the top piece, making it not possible to select all the gears.

Above left: The gear pivot base as it should be correctly bolted on top of the engine casing.

The gear pulley is also made of nylon and also held in position by a split pin. Again it has similar wear problems so should be regularly checked.

There are two different lengths of trunnion, with the longer one going through the deeper end of the pivot that houses the tie bar.

The tie bar can wear on both ends, but is more prone to doing so on the narrower end and it can get considerably elongated.