Modern Vespa

Hi i have a vespa et4 125 1999 and only had a few weeks the problem having is that when the bike is on idle the lights are dim and when you rev it they get brighter is there a reason for this or is it how it is meant to be thanks

Hi and welcome!

You posted this in the wiki section, where it won't get much attention. You probably want to post in the General Discussion area instead.

In what condition is your battery? Have you measured the voltage when idling vs when revving?

No not checked the battery yet only just got the bike should the voltage be same or different thanks

make sure the battery is topped up correctly
& fully charged , if you have a battery charger ?
before you start testing & buying new bits

charging voltage should increase as the revs increase

if unsure you tube is your friend for how to test the charging system

That's how it is - and it's nothing to do with the battery state of charge. The lights (apart from the brake light) are regulated AC, almost directly from the stator. Only the brake light is DC. The stator on an ET4 doesn't give out much voltage at idle, less than 12V AC - not enough to get the regulator to even keep it steady.

So dimming lights at idle on these early bikes is the norm.