Vespa ET4 125. Elecric start doesnt always engage properly.

First of all your service light came on so give it a service then have the service light reset then check the thermastac, water levels and the choke is working properly and all the elecric working parts are good

You might want to post this question in the specialty kitchen appliances section so that the proper expert sees it.

it's not a bug - it's a feature....some people would say...
- actually it happened on mine too after some time when it was new on both brake levers, that means it cannot be a short or something.
but, after some time I got used to it and even got to like it like that.

After getting a new set of batteries, now when I turn on the key the scooter's motor engages and takes off. I have the wiring diagram and everything looks right, what could be the problem?

first thing to check is make sure battery 12.6 volts.

Thank you for contacting FixYa with your inquiry.
This is not an uncommon behavior and we need to locate the source of the problem and eliminate the things that are not effecting the issue.
Most probable causes: Battery, Starter Relay, Start Button, Starter.
Manually start the bike and take it for a good rip and see if the battery takes/holds a good charge for the rest of the day. If you don't have trouble starting through out the day then it's a good chance you may need to replace the battery. Recommend the use of a trickle charger to keep the charge up during the week when bikes in the garage. Part# 53 Frame Parts/Wiring Harness. http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx
If your battery is known to be new or has a good charge, do you often hear a clicking sound. It might indicate your starter relay is wearing out or you have a short. Trace the wire harness and confirm insulation wear.Check starter wire and confirm the nut's tight with a good star washer. If relay - replace it. Part Number #58 Frame/Wiring Harness http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx
If the battery is known good and the relay pulls in but the starter won't engage and you can hear it attempting you may have an issue with the starter being in a bind from some internal obstruction or just plain worn out. Pull it and check it. See if it engages off the frame. You may have to take it to an alternator shop and have it re-wound. New ones are spendy. http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx
Starter Control Button: Reseat the connection and confirm it's engaging the relay. Part Number #69 chassis/Handlebar Controls. http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx
Hope this helps you resolve your starting issue. If we can provide further assistance please advise,
Best regards,
TF

they have elecric motors to press in the splines if there is a short or a blown fuse no power to hubs thus no locking check the fuses and make sure power is getting to the hubs

If you are saying the starter just spins and doesnt start the engine then your starter bendits has gone bad and is not kicking out to meet the fly wheel. You while have to remove the starter and have it repaired or replaced.

Check for bad gas -- water in gas , it is likely you have left the choke on.

hi m8,, first try this, take the handle bar start button switch gear appart,,and clean the starter button terminals that connect wen u push button in,,spray some wd40 inside the switch gear wen u put it back together,,,,,often after off roading ,,connections that the eye cant see corrode wen the bike is washed down,, any probs still ,, shout and il anserw m8,,,,,cheers