Modern Vespa

Hello

What is the wattage output on an ET4 125cc?

About 175 watts.

A huge amount of that is required for re-charging the battery after starting and for running the bike. The 125 Leader engine has very little spare capacity for 'extras' with one headlight on. Heated grips and a GPS at a pinch using about 5A - all that's spare on a good working electrical system.

Jim, while we're on the subject, would you happen to know the capacity of the Quasar 250ie alternator? If so, where did you see it? I've searched in vain...

The rule of thumb used here is that the extra continous load on a tip-top condition system is 4A for the Leader, 8A for the Quasar and 12A for the Master. Reduce for short journeys under 5 miles.

All of them can provide much higher currents for a minute or two - but that will be taken from the battery. For this reason it's a Good Idea to replace the small capacity batteries in the smaller engined bikes with the largest capacity battery that will fit in the space. This applies even if you have no extras - it gives the smaller engines a far better chance of starting in the cold.