Scootering – August 2019

SC

OOTERING

PRA

CTICAL

thiscan 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.Itispossible to get the top
piece sleeved forabetter 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been replaced by ones made from steel.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

agroove can get cut into it, greatly

exaggerating any play.Today most are

made from stainless steel and are much

harder wearing.Ta ke 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.Youwouldn'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 sitashim

underneath the top piece of the pivot to

raise it slightly and avoid the situation

from occurring. Finally,onthe 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 armand shaft

The gear selector and shaft are what go

into the casing and connect to the

wishbone. There are two types,atwo-

piece 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 boltstothe shaft, this

can come loose quite easily.Asthe 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

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

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

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.

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.

There are two different lengths of trunnion, with the

longer one going through the deeper end of the pivot

that houses the tie bar.

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