Then it's quite likely it's the battery Patsy. These SLA batteries don't last as long as car batteries since their working conditions are harder, and it's not unusual for them to only last for about 18 months. In addition, the bike may have been in stock at the dealers for a while. Once first used, the batteries deteriorate afterwards even when the bike isn't used.
The big advantage of those SLA batteries are that they are very much cheaper than other types like NiMh and lithium, so the replacement costs should not be too bad.
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