How To Clean 2 Stroke Exhaust Port

Workshop - Engine Decoke

Details for this department are for the Lambretta 175 Li Series i and two nonetheless there are many similarities between these models and other models of Lambretta threewheelers/Lambros. This information and the pictures included are provided from the 'Instructions for Repair Shops' for these models published in 1963. It is intended for informational purposes and we would recommend seeking professional person advice before undertaking anything described in the Workshop section.

The decoking of a two stroke engine is a very of import operation and should exist carried out with the maximum care, in relation to the damaging result the carbon deposits have on the operation of the engine.

The parts mostly involved in the decoke operation are:

- Cylinder exhaust port
- Piston ring grooves
- Combustion bedroom in the cylinder caput
- Piston crown

The cleaning of the cylinder exhaust port is of fundamental importance, equally the deposits which form there bring virtually a reduction of the exhaust area, thus creating an increased resistance to the outlet of the combustion gases from the cylinder.

This resistance can be translated as a loss in the useful cylinder capacity and therefore a reduction in the power output at the moment of specific consumption. Furthermore, information technology will likewise create overheating with the danger of fragments of carbon becoming loose, thus scoring the cylinder butt and causing piston seizure.

The cleaning of the piston ring grooves is also very im­portant, in as much that muddy surfaces facilitate adherence of the incombustible residues of fuel and oil.

Due to the temperature developed on the cylinder, these residues form deposits which can hinder the elasticity of the rings in so much as to cause them to stick.

These conditions as well can bring about loss of power, overheating and possible seizure.

The cleaning of the piston crown and cylinder head is necessary the carbon deposits have a depression coefficient of estrus transmission and therefore affect the cooling of the caput and piston and crusade faulty spark plug functioning.

The overheating of the carbon deposits in ratio of their low heat conductivity, tin bring about in certain zones a notable increase in the temperature, which through the reduction in the volume of the combustion bedchamber and therefore subsequent increase in the compression, tin can bring well-nigh preignition or auto-ignition, which manifest themselves past abnormal engine noises and increase engine stresses.

OPERATIONS
We requite you some illustrated details on the operations necessary for the correct decoking of Lambretta engines, so every bit to facilitate and simplify the execution.

ane	Remove caput and cylinder
2	Dismantle piston by removing the two gudgeon pins, circlips, and push out the pin by pushing it with a rod or using a gudgeon pin extractor.
three	Make clean out the cylinder exhaust port by scraping and then as to dislodge the carbon deposits, with a thin scraper. Clean cylinder and port with petrol and dry out out with air jet.
4	Make clean the exhaust gasket and ascertain if even so in usable condition. Otherwise replace with a new i to ensure perfect sealing between cylinder and exhaust tube. When plumbing equipment the gasket, be certain to fit the right style upward, the pigsty in the gasket must stand for exactly to the outline of the frazzle port on the cylinder.

5

To clean piston ; cheque the efficiency and quality of the rings; remove rings placing them on the bench and then as to be able to replace them into the original grooves. Launder piston with petrol, scrape and remove the carbon deposits from the piston crown, clean the crown with a sparse blade, do not use emery cloth, as the emery dust and metallic dust caused by the emery tin can stick to the piston and work loose during running. By using a piece of an old ring (Fig. 77) scrape the ring grooves with its broken border. Launder piston and rings with petrol and dry with compressed air. Bank check the play betwixt rings and grooves by rotating each ring on its corresponding groove (Fig. 78). Check the piston ring cease pins To check the piston ring gap, skid each ring into the cylinder foursquare to the diameter. The gap in the ring should not exist smaller than 0,three mm (0,012). If the gap is more than 0,6 mm (0,024") change ring. Refit rings to corresponding grooves.

vi	The clean cylinder head, remove carbon deposits from the combustion chamber and clean its surface with a curved scraper. Wash in petrol and dry.

Source: http://www.thelambro.com/workshop/decoke.html

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