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By tuning we would normally mean taking an existing Lambretta cylinder
or a bolt on kit and modifying it from
its standard form. Many of the bolt on kits
may already come with a state of tune straight out of the box, but
they still could be tuned and improved upon in most cases depending
on what you are trying to achieve.
The are no hard and fast set rules for the level of tune, even
though most of us would recognise or would have heard of a "stage"
tune, ranging in numbers from 1 to 10? in reality one tuners idea
of a certain stage or level of tune will not always necessarily
be the same as the next persons.
Tuning really envelopes the whole scooter, as if you increase performance
in in way you have carried out a degree of tuning. The the purpose
of this page we will concentrate on a tune being the modification
of the cylinder, piston or head, as other types of tune or modifications
have their own page.
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Increase CC |
Although not really a level of tune, and this could possibly
be also added in the bolt on kits page
I have decided to cover it here. Basically you in most case
can convert your scooter to the next available size by buying
a new piston and having the cylinder bored. For example if
you own an Li 125, you can bore the cylinder to 150cc using
a suitable piston, 150 to 175 and so on. 125/150/175 engine
casings can all accept each others cylinders. So once again
you can convert your Li 125 to 175 by either using a 150 cylinder
and bore it to 175, or by using a straight 175 cylinder and
piston assembly. When carrying out this type of conversion
you will almost certainly need to consider the following points.
You can buy or have modified a cylinder, you will need a piston
and either your cylinder head machine or a new one to match
the cc. Jetting of carburettors can
in most cases be copied from the respective conversion. By
this I mean if you have an Li 125 and convert it to Li 150
spec, in general you could follow the jetting specs from the
Li 150. In practice it would really depend on how far you went
with the increase as to jetting, timing and other recommendations.
Other capacity conversions and modifications are covered in
the bolt on kits page |
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Stage 1 |
Stage one is a very low level of tune, usually it would
involve building the engine by means of blue printing it.
By this we mean when an engine is built in the factory certain
tolerances are allowable due to manufacturing restrictions,
blue printing the engine matches exactly all components without
heavy modification to lessen these tolerances. Polishing or
ports, and maybe depending on the tuner, very slight modifications
may be carried out. Blue printing would include the jetting
of the carburettor to compensate for changes made. |
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Stage 2 |
A stage two tune you would just enter slight porting differences,
mainly the the the exhaust port to extent the time it is open.
Again pretty standard carbs and exhausts are usually used
on this type of tune. |
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Stage 3 |
Stage three would now by most tuners specification enter
in to altering the inlet side of things. Matching of inlet
manifold to the inlet port, plus slight adjustments to the
actual port timing itself. Some tuners would recommend another
type of exhaust at this stage as
well as Carburettor but standard items
can still be used. Stage three would again in most tuners
eyes be classed as a touring tune. |
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Stage 4 |
This is probably the most popular tune as it start to improve
performance quite noticeably. Larger carburettors
and exhausts would be the norm,
although in the 1980's full expansions and carbs as big as
30 to 32mm were used, in hindsight many tuners now recommend
smaller carbs for this type of tune, 25 to possibly 30mm.
While this type of tune does benefit from the larger carburettors
and exhausts, it still will work
well with more standard carbs running through the air box,
although I would recommend 22mm the smallest to use. |
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Stage 5 |
Stage five brings us into the realms of expansion chambers
and big carbs, as port timings are getting near their maximum.
Carb sizes of 30 to 34mm are usually recommended, plus the
engine would really need to be upgraded in other areas to
cope with the extra power. Items of recommendation would include
crank, bearings, clutch, electronic etc. |
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Stage 6 |
Stage 6 used to be considered pretty much race spec, but
with the advent of the TS1 and Imola type cylinder kits this
is no longer the "top tune". Transfer ports would be increased
and altered, as well as ports matched to the much larger carbs
and exhausts used. |
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Above stage 6 |
Stage seven used to include reed valves, to be fitted to
a standard Lambretta cylinder would have normally meant a
lot of engineering work. But with kits having reed valves
as standard now, stage seven could really be classed as using
one of these bolt on kits. Anything
above stage seven would be down to the tuners own modifications
and normally involve either modifying one of the mentioned
kits, or one off or an experimental type of tune or engineering
work, for example finger ports and crank case induction. Such
porting and work normally copies motor cross or full racing
technology. |
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