If your 2 stroke engine has a very fast idle or erratic idle it could be due to an air leak.
An air leak in your crankcase will cause a lean fuel mixture which in turn can lead to a fast or erratic idle speed.
It is imperative that these symtoms are investigated as the result of running an engine lean can be disarstrous.
The Theory of Air-leaks
Unlike 4 stroke engines, the two stroke engine must have a completely air tight lower end.
The normal vacuum in the 2 stroke engine's lower end will draw a mixture of fuel and air from the carburetor though the intake manifold. Once this fuel air mixture has been sealed off by the reed valve or a piston skirt, the resulting crankcase pressure moves the mixture through the transfer ports upward into the cylinder. A small "air leak" at a crank seal or an intake gasket will cause the usually perfect fuel/air mixture in the crankcase to become slightly lean...sometimes very lean. This lean mixture can quickly result in a seized piston. Air leaks are, by far, the number one cause of engine piston seizures.
If you do not have the tools to perform a pressure test (leakdown test) then you could try spraying WD40 around the carburettor inlet manifold and crankcase joint. If there is an air leak the WD40 will bubble and you may hear a change in engine speed. The crankshaft oil seals are difficult to check using this method and are a potential cause of air leaks.
The Pressure Test
DO NOT CONFUSE WITH A COMPRESSION TEST.
The step by step is :
A) Seal off the intake manifold with a plug or rubber gasket
B) Seal off the exhaust port with an automotive expanding rubber “freeze plug
If you have lost the keys to your Vespa/Piaggio scooter we have all the equipment available to get you back on the road cost effectively. If you have lost the brown master key you will not be able to add a new service key using the guide below. We have the equipment available to programme a new master and service key.
As your scooter will not be running the best option is to send us your immobiliser/ECU. We will require verification of ownership. We can then programme a new master and service key and supply a new barrel set to match. Please contact us for any advice.
If you are having trouble with your Piaggio immobiliser or Vespa immobiliser or Vespa ECU or Piaggio ECU the PDF link below is a brilliant guide to help you diagnose the problem. The Vespa transponder key and Piaggio transponder key are very expensive so look after them. If you lose the master key you may need to replace your immobiliser unit as well.
Vespa/Piaggio Transponder Key Programming
We have a good stock of blank and pre cut keys, lock sets, barrels, remapped CDI's/ECU/immobilisers and antenna etc . We have everything you need to cost effectively get your scooter up and running.
This PDF will guide you through diagnosing your transponder key problems. If you need any further assitance please contact us. We have all the equipment available to read your immobiliser/ICU and reprogram your keys.
Full throttle hesitation is a common problem with the Piaggio Zip 50cc 2 stroke scooter. Low speed response tends to be ok but when the throttle is opened beyond half way the engine dies and returns to idle. Sometimes stalling but usually resting back at idle as the throttle is released. This occurs when the engine is warm.
There are a number of potential causes to this problem. The nature of the symptoms suggest fuel starvation so this is a good place to start.
The fuel taps on these scooters have two connections. One is the outgoing fuel and one is the incoming vacuum line. This is connected to the inlet manifold. When the engine is started a vacuum is created that releases the diaphragm in the fuel tap allowing the fuel to flow.
1) Check that the fuel tap is working correctly.
2) Clean, check and thoroughly inspect your carburetor. The needle and main jet are a common cause of these problems.
3) Clean and check your air filter.
4) Check the correct operation of the choke. When started from cold after a few minutes you should notice that the revs drop as the automatic choke releases due to the engine reaching operating temperature. Poor operation of the choke can cause a number of different problems.
5) If after checking all these components check your spark plug and all components of the ignition system.
The technical talk section has been written to provide scooter technical advice, scooter technical help and scooter technical support.