Help Needed

[boilermaker1]

I took my 400f for a long drive today, bike ran great.
When I got home I turned off bike for a minute and when I went
to restart it. Battery was nearly fully dead, had to start bike with kick started.
Battery is only a few months old gel type.
Any suggestions on why battery drained? where do I start checking?

[mike the bike]

Is it charging?

[K2-K6]

Start it and while running it should give you a reading across the battery terminals of nearly 14 volts, that's the first step.

If that is true, then you're looking at the battery. If not, then it's likely the charging system.

If you post a voltage for us to see then further advice can target the problem more concisely.

[boilermaker1]

I did put a multi meter on battery later today, It read 13 volts but bike was cold and revs low.

[robvangulik]

Battery internal shorted due to overloading?
Gel batteries are meant to be loaded with a steady current of about 14,2 volts,and the SOHC's go up to 15 volts.
AGM batteries are much better suited to use in our bikes, and still maintenance free compared with normal lead acid ones.

[boilermaker1]

Cheers guys. I will give it a good warn up tomorrow as see what volts are at the battery,

[McCabe-Thiele (Ted)]

Fwiw my experience of batteries going flat has been to look at the rectifier causing a drain or ac going into the battery.

[philward]

I have had charging issues on my just rebuilt 500k2 - I had a new replacement cheapo regulator rectifier fitted and decided to go back to separate regulator and rectifier (having identified alternator was ok) - separate new rectifiers are hard to source but found this:-

https://www.ebay.co.uk/itm/202780277050

which works a treat - quick delivery from US and didn't get whacked with import duty/vat (only relevant if it turns out to be the rectifier obviously)
As previous posts, let us know the charging figures and electrickery savvy members will tell you how to check alternator, rectifier and regulator

[Bryanj]

All of the parts in the sohc four charging system are very robust unless messed with. Most charging problems can be fixed by cleaning connectors and making sure no volt drop in switches

[boilermaker1]

Thanks for the suggestions everyone... I put a multi meter across the battery this evening, 13-15 volts depending on revs.
Can I now assume charging system is okay?

[Bryanj]

If it stays at that with lights on yes

[philward]

Thanks for the suggestions everyone... I put a multi meter across the battery this evening, 13-15 volts depending on revs.
Can I now assume charging system is okay?

For your reference, have a look in Alladins cave at the (tab at the top of page) - 350/400 Shop manual page 62.