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Introduction to tuning the MB Developments way

Two-stroke tuning has been around longer than Lambretta its self.
Lambretta tuning became famous in the 1950s, 60s, 70s and more recently the mid 1980s.
The majority of these tunes were very poor and unreliable giving tuning a bad name to many people.

Tuning when done correctly is very reliable possibly even more so than standard engines.
The main failure was the piston quality, as pistons improved con rods failed and so on.
From the beginning MB Developments have aimed to improve the Lambretta tuned engine!

To date MBD have tuned over 1350 tuned cylinder kits and engines.

This article is a reference to Lambretta tuning available from MB Developments, all the information is here to help you to decide the type of tune to suit you and your riding style. There are a number of considerations you should take into account when choosing the tune for you.

  1. How much do you want to spend
  2. How fast do you want to go
  3. Do you mainly ride two up
  4. What preference of carb and exhaust do you have
  5. What type of riding do you do
    • Around town, cities, commuting to work etc
    • Country roads, motorways, road racing
    • Motorways, rallies touring

With this in mind you can read and pick through the type of tune and conversion to suit you.
Regardless of the kit to be fitted MB Developments recommend these stages of tune.

STAGE 1. BLUE PRINT

This consists of basically blue printing the engine, polish and match ports to gaskets and check out clearances.
No real tuning gain would be obtained here.

STAGE 2. TOWN / CITY TUNE

Standard 125, 150 and 175 engines are slow by todays standards; Very little work is required.
The stage 2 gives brisk acceleration and increased pulling speed both one up or with a passenger, top end speed increases a little but may struggle to keep up with modern motorway speeds.
The inlet port is roughly cleaned up which matches the standard inlet manifold and carb, the transfer ports are roughly cleaned and slightly flowed on their entry, the exhaust port is matched to a standard exhaust gasket then the exhaust port raised and polished.
The cylinder head is reprofiled to suit the piston and the compression is lowered to run on unleaded fuel.
The standard 18, 20 or 22mm carb would be employed along with the standard exhaust.
The kit was designed with towns and city commuting in mind so scooters have the power to pull away from the dangers of modern traffic.
This kit would also be at home on country roads having much more power than standard.
The limitation of the kit will always be the standard carbs and exhausts.
For more power and speed fit a 24 or 25mm PHBL carb and either an Indian big bore exhaust or a Clubman exhaust.
Fitting larger carbs and expansions is an option but is a bit of over kill as the porting spec is not large enough for it.

STAGE 3. TOWN / OPEN ROADS

The stage 3 tune is an ideal tune to suit steady speeds both two up and one up.
It is an easy ride around towns, open roads and can cruise nicely on motorways.
It lacks the acceleration and top speed for the stage 4 and 5 tune and can take some time winding up to reach top speed.
The inlet port is cleaned up, squared off and matched to 24 - 25mm carbs and inlet manifolds.
The transfer ports are flowed at their entry, flowed along their length and satin polished.
The exhaust port is matched to a standard exhaust gasket then the exhaust port is raised, widened and polished.
The cylinder head is reprofiled to suit the piston and the compression is lowered to run on unleaded fuel.
The standard 18, 20 or 22mm carb could be used along with the standard exhaust.
This tune is ideal for the slightly larger 24 / 25mm carb, Indian big bore or Clubman exhaust.
This kit would also be at home in Towns, Cities and open roads.
The limitation of the kit will be the carb and exhaust used.
Fitting a larger carb is an option but is a bit of over kill as the inlet port is not large enough.
Fitting an expansion is OK to increase top end speed.

STAGE 4. TOURING / TWO UP RIDING

The stage 4 tune is to be considered as a very good all round tune ideal for town, open roads with good pulling power for motorways and two up driving.
It has brisk acceleration and cruises nicely allowing more power to overtake.
The Inlet port is opened, flowed and polished to suit larger 28 - 30mm carbs.
The transfer ports are flowed at their entry, flowed along their length and satin polished.
The exhaust port is matched to a big bore exhaust flange and gasket then raised and widened internally.
The cylinder head is reprofiled to suit the piston and the compression is lowered to run on unleaded fuel.
The kit is ideally made for 28 -30mm carbs, Clubman exhausts for town or touring work or expansions for quicker speeds.
Any carb and exhaust could be used, but this would be a waste of time spending the extra on the tune.

STAGE 5. ROAD RACE SPEC

The stage 5 tune is to be considered as a quick road going tune capable of fast acceleration and high motorway speed.
It is ideally suited for one up riding but is quite capable of two up riding at high speeds loaded up.
The inlet port is increased in size compared to a stage 4 to match to the larger 30 - 32mm carbs required to give more speed.
The transfer feeds are lowered at their feeds then flowed and satin polished along their length.
The exhaust port is matched to a big bore exhaust flange and gasket then raised and widened internally to make a larger port.
The cylinder head is reprofiled to suit the piston and the compression is lowered to run on unleaded fuel.
The kit ideally would use 30 - 34mm carbs and run with expansion chambers.

STAGE 6. RACE TUNE

The stage 6 tune is to be considered a full race spec engine brought about though track racing.
The inlet port is opened to its maximum matched and race flowed to 30 - 34mm carbs and manifolds.
The transfer ports are opened to the maximum along their length, flowed and polished (the casing transfers require matching).
The exhaust port is opened to its maximum for race tuning then matched to a full race expansion.
The used of high compression centre plug cylinder heads could be used.
Stage 6 tuning is hardly ever used this days, the reason being a lot of work is required which in turn costs a lot of money.
For around the same money the TS1 or Imola kit could be used with the extra benefits that it brings.

STAGE 7. FULL RACE SPEC TUNE

The stage 7 tune was considered for a time in the mid 1980s to be ultimate race tune.
It was the same as a stage 6 but with the added benefit of a reed valve.
Since the introduction of the TS1 and Imola cylinder this tune is totally a waste of time.
Any tuning spec claiming to be higher than stage 7 would be considered total rubbish and pub talk!

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