These pages assume you have some mechanical knowledge
& experience of working
with Lambretta or two stroke engines. This guide has the
engine mostly dismantled (the easy bit) & removed from the
frame. The entire procedure can be accomplished
with the engine in situ, it's just a little trickier.
proceeding follow these links to remove/replace
the main bearings:
complete approximately 2-4 hours.
This is the longer crank (110mm) I'm fitting. It has padded Indian crank
webs, with a 22mm big end & Japanese conrod.
in these shots, first fit the magneto side bearing track,
ideally using heat & the correct tool (see Betta
Tools) Next turn the con rod to bottom dead centre & insert
through the crank case mouth.
With the longer crank that standard (110mm) a 3mm packing plate is
required to raise the cylinder height.
picture shows the crank seated.
Here's a close up view of the exhaust port which Taffspeed have
modified as part of their road/race tune.
workshop tool is used to ensure the crank is pulled through &
Finally the cylinder head & barrel were dowelled to ensure perfect
alignment. This also means no head gasket is required.
its time to fit the drive side components including the sprocket.
First fit the dished oil thrower over the crank.
This picture shows the 3mm aluminium packing plate & the areas that need
cleaning up around the transfer ports.
maybe lucky & there's enough slack in the chain to fit the
spline & sprocket other the end of the crank. If not remove the
This picture shows the packing plate after some light filing.
fit the remaining components onto the crank spline. These absorb any
"shock" transmitted from the gearbox/clutch to crank.
Before fitting lubricate the big end bearing with some two
the clutch holding tool in preparation for tightening the drive side
bolt. Now loosely tighten the drive side bolt that holds everything
If not done already apply some grease to the drive side oil seal
& drive side crank face.
Ensure the parts move on the spline & are seated OK (tap
lightly). Once happy tighten it right up using the correct size
socket. If this is mechanism is not fitted correctly it will foul or
crack the casing when this is fitted later!