Yuasa Motorbike battery YB9-B (DC) 12V 9Ah

The Yuasa YB9-B is the classic among 12V batteries for scooters and light motorcycles. It belongs to the powerful YuMicron series and is the standard battery for countless Vespa models (e.g. PX series with E-Start) as well as many 125cc motorbikes from Honda, Piaggio or Benelli. Thanks to its compact dimensions and high capacity of 9 Ah, it offers reliable starting power. The integrated "Sulphate Stop" technology ensures that the battery remains durable even when used seasonally and is less prone to sulphation.

Highlights at a glance

• Ideal for classic scooters: The perfect choice for many Vespa PX models (Lusso, E-Start), Cosa and various 125cc motorcycles of the 80s/90s.
• YuMicron technology: Special glass mat separators reduce the internal resistance and allow up to 30% more starting power than standard batteries.
• Sulphate Stop: A chemical treatment of the lead plates inhibits crystal formation (sulphation) at rest and significantly extends the lifespan.
• Dry pre-charged (DC): Supplied dry (without acid), so the battery can be stored for an unlimited period before activation and does not age.
• Vibration-resistant: Robust construction with glass fibre fleece protects the active materials from shocks, which is important in scooters and single-cylinder engines.
• Maintainable: The acid level can easily be checked and, if necessary, corrected with distilled water via the plugs on the top.

Features

FAQs about the Yuasa YB9-B

Will this battery fit my Vespa PX?

The YB9-B is the standard battery for Vespa PX models with battery (E-Start / Lusso) as well as for the Vespa Cosa. Please compare the dimensions (135x75x139 mm) and the terminal arrangement with your old battery to be sure, as some older models without E-Start use a smaller battery or none at all.

Where are the positive terminal and vent located?

With the YB9-B, the positive terminal is on the left (when looking at the battery from the front). The vent connection is on the right. This is important because the cables and the vent hose in the battery compartment are usually designed for exactly this arrangement.

Do I need to charge the battery before installation?

Yes. After filling with acid, the battery should rest for approx. 30 to 60 minutes ("outgassing"). Then a full charge with a suitable motorbike charger is mandatory to ensure full starting power and maximum service life.

What is the difference to the 12N9-4B-1?

The YB9-B is the more powerful further development (YuMicron) of the classic 12N9-4B-1. It has the same dimensions and terminal arrangement, but due to the more modern internal construction offers higher starting power and a longer service life. It can easily replace the 12N9-4B-1 (upgrade).