Bolt on kits

By bolt on performance what we really mean is a cylinder kit that replaces your original item. We use the term loosely as in reality you will need to check, overhaul and in most cases upgrade the rest of your engine. With any performance kit you fit onto your Lambretta, it will be the nature of how it works increase the rpm of your engine. This can and will lead to increased wear, more load on all working parts, and more then likely more vibration. Of course there are lots of things you can do to upgrade your engine as well as fitting the performance kit you choose. It cannot be stressed enough, when considering improving the performance of your engine, you must include in your budget upgrading and overhauling the complete engine. Lets face it and take one part as an example, if your crank fails, it will more then likely wreck the expensive kit you have just fitted, so fix this first! A "bolt on kit" may be a heavily modified Lambretta cylinder and piston assembly, or a totally different design. In practice you take off your original cylinder and replace it with one of the items listed below. Of course as we have said, depending on the kit you may or may not need to add further parts or modifications and upgrades to your engine and other parts, but explanations are below.


We have tried to give a rough estimate of cost and performance, this is intended as a rough guide only due shops prices as every thing is life can differ slightly.


On the performance side of things the speed quoted again is a estimated guide, series of machine, riders weight, exhaust, carburation, level of tuning and by who, wind, type of area you live in, flat hills etc all can and will affect this.

Kits for all series 1/2/3 machines from 125 to 175cc

175

There are quite a few shops selling 175 cylinder kits. Basically these are cylinders made by Scooters India Limited and other suppliers in Italy, they come with a wide Variety of pistons dependant on where you purchase the kit. It should be noted that you should ask your supplier if they check the piston to cylinder clearance, as many of these kits are simply a cylinder and piston, and may not be matched. We suggest you always check yourself in any case! Port layouts and level of tune can only be described as small to fairly standard, although as with any other standard cylinder you can tune the cylinder for more performance. Some machines such as SX and GP 150 may not even benefit from fitting on of these kits unless it is tuned further. As long as all engine components were in good condition, carburetor re jetting would be the only thing needed to be added. Of course you could add larger carbs, different exhausts and extra tuningfor more performance, but more upgrades to the rest of the engine will then be needed.
Average Cost - £100 to £120 (cylinder kit only)
Average top speed - 60 to 65

SR

Produced by Scooter Restorations, with design input by MB Developments & Ian Easton, the SR promised to be the first true bolt on cheap performance kit, well made and modern in design. In reality the kits have been dogged by bad press, problems with the initial design of the piston being at fault. Paul @ SR has been working hard on replacement pistons, no news is available at present. The SR kit is a an alloy cylinder with a cast liner meaning it can be rebored. Porting is based on the layout of the TV175, but of course further tuning can be carried out. The kit is available in different sizes, 62mm gives 175cc, and 64mm gives 185cc. All pistons will fit Li/SX/GP style of crank, it appears a TV type piston is not available, but we could be wrong. Plus points of the SR kit is the kit is easy to fit, and a direct replacement for any 125/150/175 top end which should give more speed for all engines. The only negative points to the kit are the piston problems, and the casting within the porting area is a bit on the rough side. Having said this SR do sell bare cylinders so another type of piston can be used, and the porting although a touch hard, can be cleaned up.
Average Cost - £160 (Complete cylinder kit) / £125 (cylinder only)
Average top speed - 70 to 75

Mugello

186cc, alloy cylinder with a nicasil lined cylinder. Basically these cylinders are stage four tuned as standard, but with larger flowed transfer ports then found in standard iron cylinders, and come with a piston from the Imola kit, without the windows cut. the bore of 64mm gives a 185cc from a standard 58mm stoked Lambretta crank. Chocie of piston fro Li/SX/GP or TV lenght of conrod means this kit will fit all 125/150/175 engines. The alloy cylinder has a nicasil lining, which should give longevity to the cylinder. The inlet port of the cylinder can accept all standard Lambretta manifolds from 18/20 to 22mm for use with standard carburettors. Mugello also supply a large manifold which is suitable to be used with Dell'Orto PHBH 26, 28 and 30mm sizes of carb. It should be noted if the larger manifold is chosen, to get the optimum from that set up, the outer inlet would need to be opened up and matched to the manifold. Other suppliers also make manifolds for most types and sizes of carburettor. The exhaust port accepts standard Lambretta U bend types, so a wide choice of exhausts can be fitted. Benefits of the cylinder is an all alloy construction, meaning less weight and better heat disspaction, less chance of heat sezuires. The dissadvantages of the kit are if problems should occur and the nicasil is damaged you cannot rebore this. How ever the kit manufacturers claim they can repair & re nicasil the cylinder with a new psiton for under £100, which could work as cheap as a piston and rebore.
Average Cost - £220 (standard) to £300 (tuned) (cylinder kit only)
Average top speed - 70 to 80

Gran Turismo

Designed and manufactured in the UK, the GT kit is an iron cylinder with large gas flowed transfers, built in reed valve & boost ports. The kit comes with Japanese pistons and Rotax reed valve. The exhaust port is the standard Lambretta pattern and is suitable for any big bore or expansion pipe system with a standard flange. The kit requires the use of a larger 25mm PHBL Dell'Orto, but other options on manifolds allow larger VHSH flat- slide carb option at the expense of a battery tray. Standard format for the kit is 186cc, but larger versions of 200cc and 215cc are available. The 200cc kit retains the use of a standard 58mm stoked crank, whilst the 215cc version requires a 62mm stroke crank. Many other versions are available to shops/trade for more specialised tuning. Almost all engine parts would need to be upgraded to cope with the extra power, especially recommend is crankshaft, electronic ignition, clutch and bearings
Average Cost - £285 (standard 186) tuned and larger versions extra
Average top speed - 70 to 85

Suzuki 185

The Suzuki kit uses an original Lambretta cylinder, bored to 64mm to accept a Japanese piston. In standard format this kit can be fitted with few modifications to jetting, again engine parts would need to be in good condition. The basic kit can also be improved upon by a Variety of different tuning options as supplied by various tuners around the world. With the new SR or Imola alloy cylinder kits now available, this type of kit has declined slightly in popularity, but still worth a look even though it is old technology.
Notes of conversions using Japanese and or other types of pistons
Average Cost - £200 to £250 (cylinder kit only)
Average top speed - 70 to 75

Imola

With a higher state of tune to the Mugello kit, the Imola and Mugello share similar technoligy. Both kits are made by Imola racing, but the Imola Made up of an alloy cylinder with reed valve induction, lightened piston, the kits also comes with inlet manifold, gaskets, etc needed, although not many shops offer a cylinder head as standard. Manufacturers claims of over 15bhp in standard form would make a scooter kited with this faster then standard 200cc scooters. Manufactures also claim tuned versions can go up to 24bhp, which is again more power then a standard TS1 and some tuned ones. The 200 kit uses its own longer stroke crankshaft to make up the extra 15cc, and does need the crankcase machine to accept the crank, further increasing the cost over the smaller 185. The kit requires the use of a larger PHBH or similar type carburetor which exists from the opposite side to standard, if your Lambretta has a battery tray this would have to be removed because of this. A new exhaust is also needed as the shaped and fittings of the exhaust port are totally different to standard. There are many exhausts available as the Imola and TS1 share the same design of exhaust port, you can choose form a standard looking big bore up to a full race system. Almost all engine parts would need to be upgraded to cope with the extra power, especially recommend is crankshaft, electronic ignition, clutch and bearings.
Average Cost - £300 (cylinder kit only)
Average top speed - 75 to 85

Kits for all 200cc engine cases.

Honda 205

Again a very similar conversion to the smaller Suzuki conversion, this one takes a standard 200cc cylinder which is then bored to 67mm to take a Honda MTX piston. In standard un tuned format, the use of standard carb and exhaust can be used, but more gains can be made with fitting larger carburetors and expansion exhausts. Higher states of tuning can easily be carried out but engine components would need to be upgraded. Crank, electronic ignition, clutch and bearings at minimum.
Notes of conversions using Japanese and or other types of pistons
Average Cost - £200 to £250 (cylinder kit only)
Average top speed - 75 to 80

Honda 225

Standard 225 conversion kits are based on the standard cylinder, which is bored to accept a larger 72mm piston. Most use a standard Lambretta style piston, others can be modified to accept Japanese and other types of pistons. On the whole although standard carburetors and exhausts cane be used, they will restrict power and you should really consider larger carburetors and exhausts to achieve the best power.
Average Cost - £150 to £200 (cylinder kit only)
Average top speed - 75 to 80

Mugello

200cc & 225cc, the Mugello is an alloy cylinder with a nicasil lined cylinder, the same as the smaller 186 version, but this is made for the 200 casings. Basically these cylinders are stage four tuned as standard, and come with a piston from the Imola kit, without the windows cut. The use of standard carburetors and exhausts can be retained, or larger carbs and performance exhausts can be added to boost power. Further tuning of the kit is also possible.
Average Cost - £180 (standard) to £300 (tuned) (cylinder kit only)
Average top speed - 70 to 85

Rapido

The Rapido is available in a few choices, 200, 225cc or 250cc, mild tune or race spec. The Rapido Classic (mild tune), is only in 200cc with a very mild state of tune intended for use with a standard carburetor and exhaust. (although you can tune the classic to the same spec as the race Rapido). The Race Rapido 200cc & 225cc, is a tuned kit designed for use with both a larger carburetor and an expansion system. The newer 250cc version of the kit on the market uses a larger 60mm stroke to achieve the extra cc, in doing so provides more torque. The manufacturers also recommended the addition of a Race Crank for all these kits.
Average Cost - £150 to £200 (cylinder kit only)
Average top speed - 75 to 80

240 & 250

240/250 conversions used to be popular but required a fair amount of engineering to make them. Only a handful of shops offered such conversion, but there are now more powerful "out of the box" options that have really seen the 240/250 conversion virtually disappear. This type of conversion in now pretty much limited to self built or one off commissioned products rather then available off the shelf.
Average Cost - £200 to £300 (cylinder kit only)
Average top speed - 80+

Monza

The kit is the larger version of the Imola kit for 200 sized casings and can be purchased as a 200cc, 215cc or 225cc. The manufactures have also made a limited number of 240cc version, but these mainly exist with dealers under going testing. Made up of an alloy cylinder with reed valve induction, lightened piston, the kits also comes with inlet manifold, gaskets, etc needed, although not many shops offer a cylinder head as standard. The kit requires the use of a larger PHBH or similar type carburetor which exists from the opposite side to standard, if your Lambretta has a battery tray this would have to be removed. A new exhaust is also needed as the shaped and fittings of the exhaust port are totally different to standard. There are many exhausts available as with the Imola and TS1 the Monza also shares the same design of exhaust port, you can choose form a standard looking big bore up to a full race system. The only down side is the 215 and 240 versions need a 62mm stoke crankshaft, which can make this conversion even more expensive
Average Cost - £300 (cylinder kit only)
Average top speed - 80 to 85

TS1

This kit is probably the ultimate kit for making any 200cc Lambretta go fast. Available in 200 or 225cc the TS1 has been around since the mid eighties and has proved to be a reliable and popular choice. Made up of an alloy cylinder with reed valve induction, lightened piston, the kits also comes with inlet manifold, gaskets, and cylinder head. The kit requires the use of a larger Amal, Dell'orto or similar type carburetor which exists from the opposite side to standard, if your Lambretta has a battery tray this would have to be removed. Flat slide versions are recommended if you do not want to cut holes in your side panel to allow the air to get into the carburetor A new exhaust is also needed as the shaped and fittings of the exhaust port are totally different to standard. There are many exhausts available as with the Imola and Monza also shares the same design of exhaust port, you can choose form a standard looking big bore up to a full race system. The Manufactures of the kit do not offer and tuning above the standard kit, lets face it it is highly tuned compared to standard in the first place, but there are many shops that will tune even further. At the top end of the tuning scale, claims of up to 40bhp for a tuned racing version would need a whole host of other modifications within the engine to cope. Almost all engine parts would need to be upgraded to cope with the extra power, especially recommend is crankshaft, electronic ignition, clutch and bearings.
Average Cost - £260 to £280 (cylinder kit only)
Average top speed - 80 to 90

Notes of conversions using Japanese and or other types of pistons

Due to the improved design characteristics of modern Japanese pistons and piston rings the use of these items has extended the scope of Lambretta tuning far beyond what was reliably possible with the original items. The original items were more than capable of coping with operation of standard engines but as tuners/racers sought to increase power outputs the stresses placed on these components were raised to a level which caused regular component failure. The original piston design is one of the first weak links discovered when tuning an engine.
The fundamental problem in using these pistons is that they were not designed for use in a Lambretta cylinder or to be used on a standard Lambretta crankshaft. All standard Series III Lambrettas use 58mm stroke crankshafts, use a cylinder of approximately 100mm to 101mm, and a con rod length and piston compression height equalling 146mm (TV175 =3D 116mm + 30mm, all others =3D 107mm + 39mm). If any one of these factors was different in the engine for which a Japanese piston was designed then the piston cannot be used in a Lambretta engine unless components are altered or substituted to compensate. The most common alterations to use a Japanese piston are to use a different length con rod or to alter the effective length of the cylinder. Depending on what is required a cylinder height can be shortened by removing material from the head or base gasket surfaces, or increased by adding packing plates to the base gasket face. To further complicate matters the port timings and positions will need reworking to suit the new piston arrangement.
To further complicate things, an alteration to any single factor will require further compensation to be taken into account, even when using the same Japanese piston. For example, if a Suzuki 185 piston is used with a 116mm con rod then the cylinder will need to be raised but if used with a 107mm con rod then the cylinder will need to be machined shorter. If the stroke of the crankshaft is also altered then yet further alterations need to be made. With crankshafts being commonly offered in 54,58,60,62mm stroke varieties and Japanese con rod conversions being offered in addition to the original 116mm and 107mm lengths, the possible combinations are virtually limitless.
With so many British dealers offering numerous Japanese (and other) piston conversions, each requiring their own individual component specification, it becomes very difficult to supply replacement parts, offer advice or identify components for a piston conversion that another dealer has developed/supplied. For this reason alone, most dealer kits will have an individual reference number marked on the cylinder.
It must also be noted that Japanese pistons often have a different crown profile to work in conjunction with the cylinder head combustion chamber of the original Japanese engine. This means that the Lambretta cylinder head needs re machining to work in harmony with the piston used.
Also, it is not unusual to find that the Japanese pistons employed today were intended for use in aluminium cylinders which cannot be re bored but rather allow for wear by offering piston size increases in minute 'grades', making them pretty useless in iron cylinders if the existing bore becomes damaged beyond the grade sizes available. Some pistons also are supplied with harder rings and it is not unknown for cylinders to wear far more quickly then you would normally expect.
For all of the reasons listed, it should be quite clear that there are many issues to address when trying to develop a Japanese piston conversion. The dealer supplying the kit will need to know which model of Lambretta the kit is to be used on and what, if any, engine components have been altered from standard specification. The conversions listed are the more commonly supplied kits, for fitting to engines running standard crankshafts and con rods.