My Scooter Wont Start - Lambretta / Vespa

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My Scooter Won't Start

OK so we have stated the obvious, now it is up to you to check the obvious as well, time after time people call us for advice and totally ignore the basic things. Never assume the worst, start at the very begining at lets see if we can get it going!

Your Lambretta (or any scooter for that matter) needs three things to get it going. A) a spark delivered at the appropriate time B) You must have good-quality fuel/air mixture, and C) compression to compress and provide a suitable bang to get the engine going! So with all those three items, an engine will run, so now to find out which one is missing!

A) Checking For Spark

We just need to start at the begining and work our way along the line of where the spark is produced, and see where it stops working. To contradict what we have just said, the first and most simple thing to do is check for a spark at the plug. Remove the spark plug from the cylinder, check its general condition, insert the plug back into the HT cap, hold the plug against the engine casing, and kick the scooter over (remember to turn the ignition on, and hold the HT lead not the spark plug so you wont get a shock!)
The spark plug should produce a nice blue spark, if it produces a weak spark, check and adjust the gap on the plug, and try again. If you still have a weak spark, or you have had no spark at all, then follow the guide lines below.

1) From the stator plate there will be a green wire, remove this wire from where it is plug in, brush the wire on the mag housing and kick the scooter over and check for spark again. If no spark from the green wire, check the following
Points and condensor :-Check correct timing for the opening of the points, most accurate way is bulb and battery.
Check and clean the contacts of the points.
Replace contact points and condenser if still no sparkElectronic :- Using a multi meter on a 2k setting, check the read outs give the following (earth your - probe on the meter to the mag housing)Green wire should read around 400 or just below
Red (sometimes yellow) wire should read close to 90Should you want further advice and help with SIL/Indian electronics, we have written a guide on how to check these systems out, this can be found on our help and downloads page.

2) The next step is if you do have a spark on that green wire, and do have the correct readings from the electronic stator. We are now going to suspect the ignition coil, or for electronic systems the CDI. Just before we do, if you have not done so already with the previous step, take the green wire off the CDI or coil, and brush it against the frame whilst kicking the scooter over. If you have no spark here, you might just want to check the ignition switch or cut out button is not faulty. Take the headset top off, and disconnect the green wire from the main loom, from the junction, and make sure this does not touch any other wire or body work. Quickly check for spark again, if you have a spark now, either your ignition or cut our switch; which ever one you have fitted, is faulty.

3) OK presuming you still have to find the fault, replace the coil or CDI unit with a known working one and try again.

4) The last step is to check and eliminate the HT lead, and the HT cap, again possibly the easiest method is to replace.

B) Checking For Fuel

Checking for fuel is for both no flow and too much flow. To start with undo the fuel pipe from the inlet banjo on the carburettor, hold the hose near to the banjo and turn the fuel tap on. If there is no flow, or little flow, take the petrol cap off and try again. If the flow improves, the fuel cap breather, or if an early Lambretta petrol tank, it also has a breather tube in it, this breather it blocked. If taking the cap off does not improve flow, then the internal fuel tap filter is blocked.
If you have good flow to this point, remove the float bowl, refit the fuel pipe and allow the float to drop and check the flow coming out from the carburettor. check the level of the float, and the condition of the float retaining pin, and the float needle. Also


One of the most common questions we get asked is about poor hot starting, this is VERY common.
Some things to check are :-Wrong grade of spark plug / wrong gap,
Dirty air filter, (includes poor quality air filters that are either too small, or incorrect paper elements)
Incorrect points gap / wrong timing,
Worn rings / worn piston bore,
Float needle worn,
Throttle slide worn
Wrong pilot jet size / blocked pilot jet.
Choke on, either worn choke or check choke cable is adjusted correctly
Air scoop blocked, or wrong size scoop / airbox for carb.
Break down of coil
Break down on pick on on electronic kit
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