How to choose the right cylinder-piston kit?

The essentials to know before choosing your cylinder-piston kit

Le piston is a rigid part of generally circular section sliding in a cylinder of complementary form.

Difficult to navigate among the different models of engine cylinders AM6 ou Derbi for 2 time engines. To help you, we have drawn up a small comparison between the cast iron cylinder and the aluminum one.

For 4 time engines, the comparison is also applicable.

COMPARISON FONTE - ALUMINUM:

Cast iron cylinder	Aluminum cylinder
High resistance	Less resistance
Easy assembly	More complex assembly
Ideal for everyday use	Good basis for preparation
Heavy material	Light material
Low maintenance	Regular maintenance
Lower price	High price
Templonger heating time	Tempshortened heating
Templapping s from 300 to 500 kms	Templapping s from 150 to 200 kms
Semi-synthetic oil	100% synthetic oil

The pistons are subjected to mechanical stresses resulting from the combustion pressure of the gases and to thermal stresses, due to the temperature difference between the piston and the burnt gases. These constraints explain the choice of materials, cast iron or aluminum.

Aluminum is often preferred to allow better heat evacuation. Indeed, the piston and the aluminum cylinder expand almost at the same time, that is to say that there is less risk of cold clamping, unlike the cast iron cylinder.

With a cast iron cylinder, the piston heats up (expands) faster than the cylinder, so there is more risk of cold squeezing.

Engine cylinders Derbi Euro 1 egg Euro 2 : the peculiarity is in the circulation of the cooling liquid which arrives directly on the cylinder par the hose and spring par the cylinder head, unlike the engines AM6 ou Derbi Euro 3 and 4.

Cylinder head for engine Derbi Euro 1 egg Euro 2 is simple, the water inlet is on the side of the cylinder and the outlet is par the cylinder head unlike the engine cylinder head Derbi Euro 3 which is of the two-part type with the coolant inlet located under the cylinder as with the engines AM6. Coolant circulation is better designed and cools the combustion chamber better.

For 4 time engines, mainly mÃ © caboÃ ©tes of Chinese origin, there are several types of piston cylinders for 139FMA-139FMB Horizontal and 139FMB vertical type. The cylinders are made of cast iron or aluminum. They are less complex because of the cooling system par air.

EXAMPLES OF BRANDS / MODELS ET OF THEIR ASSOCIATED ENGINE

AM6	DERBI EURO 1-2	DERBI EURO 3-4	TYPE AM6	FMB 139	139 FMB-B
Aprilia RS before 99	Cagiva Mito	Aprilia after 05	Hanway	Eurocka	Eurocka
Beta RR	Derbi GPR before 06	Derbi Senda X, trem, DRD Pro, X-race...	Generic/ KSR	Jincheng	Masai
Malaguti XTM/XSM	Gilera SMT, RCR, GP ...	Gilera SMT, RCR...	Masai	Kinroad	Mash
MBK X-limit	Derbi Senda SM	Nox KLE	Razzo	May Power	Orion
MH 10, Furia ...		SpeedCool	Ride	Motrac	Skyteam
Peugeot XP6, XR6...		Valenti		Yamasaki
Rieju RS3, MRT ...
Yamaha TZR, DT ...

Conclusion

- Cast iron kit: Reliable, slightly higher performance than stock for 50cc, stock crankshaft for 50cc and reinforced crankshaft, bearings and spinnakers for 70cc and +.

- Aluminum kit: Torque and sharp, performance superior to cast iron kits, to be maintained, mandatory replacement of several low and high engine parts, especially on engines AM6.

Increasing the horsepower of a motorcycle is the dream of many riders, regardless of the cylinder capacity of the two-wheeler. When technically possible, this kind of intervention very often outlaws the owner and excludes him from the benefit of his insurance.

It is therefore necessary to reflect and become aware of the risks incurred in the event of non-compliance with the legislation.

Examples of common models

CYLINDER PISTON AM6 MINARELLI

CYLINDER PISTON DERBI

PISTON CYLINDER 139 FMB

MORINI PISTON CYLINDER

Learn more about piston cylinders

Benchmarks

An original type cylinder is more efficient than an entry-level cast iron cylinder. A new piston must not be fitted to a worn cylinder.

The cast iron kits replace the original cylinder very well and provide very little additional performance; cast iron kits are renowned for their reliability, these kits are often purchased separatelyar people who do not wish to change the crankshaft or those who change their original type cylinder

50cc aluminum kits offer very good performance. It is necessary to change the crankshaft and change the bearings and oil seals. They will be paired with either a 19mm or 21mm carburetor. They are more expensive and less reliable than cast iron ones. They also require more maintenance than cast iron kits.

More expensive than the adaptable models, the original cylinder kits benefit from an excellent quality of finish guaranteeing performance and resistance. They meet homologation standards.

For a boxed motorcycle, the cylinder will be less than or equal to 50 cc. The kit will then be approved. Some kits necessarily require a change of parts such as the crank shaft needle cage...

Point on unclamping

When you really want to increase the power of an engine, one of the main parts to replace is the cylinder. It should be taken into account that the modification of the engine characteristics by changing the cylinder requires to adapt other parameters such as theexhaust, carburettor, transmission, Ignition, etc. to the new cylinder.

The de-clamping authorized from 2016 can only be done par professionals and leads to administrative formalities such as change of vehicle registration document, homologation of the converted vehicle, insurance procedures, obligation to hold a driving license.

The "full unclamping" of a motorcycle since 2016 concerns only a certain category of vehicles, in particular two-wheelers equipped with an anti-lock braking system (ABS ) as specified in article R. 311-1 of the Highway Code. This release concerns any motorcycle prior to the Euro4 standard, regardless of its category, also allowing you to consider unclamping an 50cc motorcycle.

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