I have a Triumph Street Twin Motorcycle (2016) that has generally low milage and running well over the years. When trying to ride recently the bike stuttered and engine didn't kick in, after a few repeated attempts the stuttering didn't happen either and just no start.

Thinking the battery might be low (due to infrequent use) I used a jump starter battery and bingo! Working bike! However, after some riding and giving the battery a chance to recharge, once turned off the engine refuses to restart again.

Next I tried removing the battery and using a mains charger to full recharge the battery, after some hours and the charger indicating the battery was at 100% I popped the battery back in and still no luck.

So a fully charged battery won't start the engine, but an additional jump starter battery will.(Connected to the same terminals / contact points)

What could the issue be? and how can I fix this at home? (Given this has taken a while so far, my MOT has lapsed so getting the bike to a mechanic would be technically illegal)

  • Welcome to Motor Vehicle Maintenance & Repair! Oct 20, 2023 at 10:39
  • What happened when you try to start after charging with the mains charger? Did the starter motor run as normal? Was the starter labouring?
    – HandyHowie
    Oct 20, 2023 at 10:42
  • There may be two problems; a worn out battery and/or the charging system isn't recharging the battery. If I'm not mistaken, motorcycles use a magneto with electronics to supply electrical needs while recharging the battery.
    – F Dryer
    Oct 20, 2023 at 17:57
  • I had exactly the same issue with my BMW F800ST. The problem was that the alternator was completely burned, did you check that?
    – Sirfara
    Feb 20 at 10:00

1 Answer 1


You need to have the battery load tested as well as get it checked to see its health. More then likely, the battery shows on the charger it is at 100%, but really what the charger is saying is its at 100% of the charge it can take. If it'll start off of a jump pack (or battery), but not off of your main one alone, it all leads back to the battery.

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