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Cold starting question - SOLVED

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tris:
Morning All

My BMW F800GT turns over slowly when cold but once warmed up spins over like a good 'un

I initially thought that the battery was on its last legs (it was the original from 2019) so replaced with a new Yausa YTX14H-BS but still have the same problem.

Charging seems to be OK circa 14v with everything switched on or not at different throttle settings

I checked the voltage when I got home after a ride yesterday and it was at 13.0v dropping to 12.5v after a few hours and still 12.5v this morning.

Have I been unlucky an got a duff replacement battery or is there any else that can give these symptoms?

Cheers
Tris

paulbricey:
Probably worth checking all the usual suspects (clean & tighten all earths, check switchgear, check relay seats, check lazy relay, starter motor itself (my Griso starter needs periodic clean inside) etc etc.........but IMHO the quickest way to bypass working through all these checks is just carefully run the battery direct across the starter motor connections (with the starter in bike as normal and ignition on). If it spins and starts faster/normal with large thick wires direct from battery, then it is one of the things in the list !!...if not then it's either the starter itself or battery...

tris:
Cheers
That makes sense EXCEPT that this thing is a full Canbus bike and I'm not sure what I'll FUBAR if I go that way.

 I might put the bike on the charger and try and immediately start it as soon as I take the charger off.

That might show if it's a weak new battery before I rave all the farings off so that I can get the battery out for testing

paulbricey:
I know what you mean about sensors/proprietary bus networks & power spikes & TBH up to few years ago I used to avoid even putting charger on battery on our cars (they are slightly newer than my bikes  :laugh:) without disconnecting the car supply ......BUT more recently I've charged/jumped/shorted etc loads of 'modern' stuff without anything going bang.

DoubleGuzzi:
You don't mention battery type; I hope that you're using at least a Gel or AGM one.
There are a few variables, such as the starter motor gear ratio, that determine cranking speed but almost exclusively, you'll want a battery with high Cold Cranking current (CCA). Battery technology can greatly influence starting , for example the only true recommendation for a 2000 Laverda 750S Formula was/is an Odyssey PC680. Yup, other batteries can be used but not consistently/reliably. Less expensive, though typically a good choice are the Motobatt and Exide (upper/higher cost) ranges. Availability of particular manufacturers will vary Worldwide.
Lithium (LiFePo4) batteries offer a strong CCA but bring other 'challenges', lack of capacity being the biggest pain, IME.

Note: Yuasa batteries always had a good reputation (in the UK certainly) but if a 'standard' wet cell type, then not really 'up to the job'. Particularly with wet cell types, 'duff' ones do happen.

(I used to be a technologist that lab. tested automotive batteries. Dissecting them was 'fun'! )

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