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Aankondiging: Geachte klant I.V.B met verbouwingswerkzaamheden zijn we van 31-05-2021 T/M 06-05-2021 GESLOTEN.

Cylinder & Head

Cylinder and engine block scooters

"The most common cause of a hot or jammer is a lack of oil: using 4-stroke engine from factory with minimal to no oil, it is highly recommended to check your oil regularly!"

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Engine block

Crankshaft & parts

Pistons & parts

A cylinder consists of a cylindrical sleeve closed on one side, two-stroke cylinders have two or more openings for, among other things, flush ports and the inlet. For four-stroke the following applies: fuel is injected on the sealed side. With a petrol engine, it is periodically ignited by means of an ignition system.

Two-stroke and four-stroke engine blocks are both piston engines. The difference between the two is mainly in the way the fuel and air mixing belt enters the cylinder and the exhaust gases leave the cylinder.

  • With 2-stroke this goes via the flush ports.
  • With 4-stroke this goes via the valves

It is a small difference, but it ensures that a 2-stroke and a 4-stroke totally differ in their advantages and disadvantages.

The inlet and outlet valves are driven by a camshaft which either directly (with an overhead camshaft) presses the valves or indirectly (with an underlying camshaft) the valves press via pushrods. The drive of an overhead camshaft takes place via a chain, belt or gears from the crankshaft. The piston drives the crankshaft via the connecting rod, which converts the up and down movement into a rotating movement..  

When the piston is down, the intake valve opens and the air is sucked in by the carburetor that mixes the petrol vapor. When the piston is down, the inlet valve closes and the piston moves upwards. When the piston is almost at the top, the spark plug ignites the mixture and is then pushed down with high force.

When the piston is below, the outlet valve opens, the piston goes up again and the burned gases are pushed out through the piston via the outlet valve.

The piston then goes up again and closes the outlet valve and opens the inlet valve as soon as the piston goes down. This process is then continuously repeated.

Zuiger set
Krukas scooter

If you want to know more about the operation of the engine, please check:




Question: While I ride with my scooter the scooter falls back in speed or out! But he usually starts again after this! What is going on should I replace my battery?

Answer: No, this is not your battery. There can be several reasons why this happens, however, the most common cause is a shortage of oil or waiting too long to carry out your servicing. It is very likely that your scooter has a so-called "Warm runner" or also called a "jammer". To solve this, only the cylinder can be replaced. You can drive on but it is inevitable that the scooter goes at a certain moment. Your oil consumption will also increase considerably below.


Frequently Asked Questions