Battery / starter motor again!!!

[JohnnyBoxer]

So that would be a starter failing through 'heat soak' when the engine is hot - Ill give your suggested test a go

I’d bet if it’s the original starter and if the bike has infrequent use, then it’ll be ready for a new one after 13 years
Treat it to a new battery too
How’s the alternator charging ?

 

[Santa-2512]

Holy thread resurrection Batman !!

 

[Wreford Miles]

Sounds like starter motor failing and drawing too much, when cranked
It pulls the battery down
Do a voltage test
Off
On
Cranking
That will yield your answer, if when cranking it drops to 10v or less then it’ll be a starter
Happened with my 1150 even with a brand new battery

Voltage ignition off 12.6
Voltage ignition on 12.3
Voltage when cranking drops to 9.8 but was starting
When the engine was running, charging was fine

So it seems it’s the starter motor - But here’s a thought:

Thinking about how I use the bike, I’d say the starter motor gets very little use. I start it I ride it I park it up, it’s rare that I’m stopping and starting during a ride. I wonder if I should just do a bit of stop start to see if the starter frees up

 

[Santa-2512]

Voltage ignition off 12.6
Voltage ignition on 12.3
Voltage when cranking drops to 9.8 but was starting
When the engine was running, charging was fine

So it seems it’s the starter motor - But here’s a thought:

Thinking about how I use the bike, I’d say the starter motor gets very little use. I start it I ride it I park it up, it’s rare that I’m stopping and starting during a ride. I wonder if I should just do a bit of stop start to see if the starter frees up

Just buy a new starter motorab and be done with it

Its lasted this long lol treat yourself

 

[seahorse]

I imagine your bike has a few miles on now. Might be worth taking the starter out and doing a strip and clean. New brush pack not expensive if they look worn. Done just this recently myself as well as new cables connected in parallel with existing ones. Made a bit of a difference for me anyway.

 

[JohnnyBoxer]

Voltage ignition off 12.6
Voltage ignition on 12.3
Voltage when cranking drops to 9.8 but was starting
When the engine was running, charging was fine

So it seems it’s the starter motor - But here’s a thought:

Thinking about how I use the bike, I’d say the starter motor gets very little use. I start it I ride it I park it up, it’s rare that I’m stopping and starting during a ride. I wonder if I should just do a bit of stop start to see if the starter frees up

Bingo
My 1150 did the same
It was the starter motor failing
New Valeo Starter and all has been fine for last 18 months
You don’t want to buy a new battery, only for the starter motor to wreck it

 

[Slipperyeel]

From everything I've seen lately with BMW motorcycles, full lithium batteries are a complete disaster ... I've heard tell of a hybrid battery that some are using in the UK and they seem to like them. Hybrid being both AGM and lithium. But a new AGM is a solid bet and many of the new 1300s that came with lithium are being converted back to AGM for the most part. You do have to tell the computer .... Or address the perimeter and adjust the charging voltage to the AGM level.
I also seen a guy at west denver BMW that had a Ural, a really neat machine, and he had put a lightweight lithium battery in it. It caused him many problems on a basically brand new bike, fuel pump went out, would start several times. A mechanic came out to help with the bike as it decided not to start when the fellow tried to leave. Myself and the mechanic talked him into putting an AGM in it ... It started right up and he drove it home ....

Well, on the 1300 you might be right, even possibly on the 1250 as any drop below a set amount, computer says no.

But my experience is on the twin cam and it's not what you describe. Lots of misinformation out there. My own view is based on some years of experience with this type of battery. I even bought another one, with a higher Amp hour rating to help fill the gap in the worst case scenario (winter, with heated clothing on, heated grips on and in traffic) and remove some load of the alternator. Maybe overkill, but not really after having done the numbers.

On the hex head and twin cam, I would recommend a lithium battery