Author Topic: Intermittent starting  (Read 381 times)

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Offline richtea

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Intermittent starting
« on: January 17, 2025, 09:38:49 pm »
I have an intermittent problem with starting.

Listen to/watch the video:
www.poqit.com/starter_fail.mp4

It only does this once in a while - maybe every 5th / 10th time. Occasionally (as in the video case) it doesn't start several times in a row.

I took it into BMW to investigate, and they couldn't reproduce it.
I then took it out several times until it failed again and then took it back to BMW. They listend to it (it only failed for about 2 seconds on the BMEW NOG premises and then fired, but that convinced them to replace the starter motor, just before Christmas.

It's taken a while to get back out and ride due to weather, but now I find it's not fixed.

I know the first step is to take it back to BMW, but does anyone have any hints on what else might go wrong - since it's not the motor itself?
(Actually, the ideal first step is to break it permanently so it can be diagnosed properly, but whatever.)

Thanks in advance...

Offline Matt

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Re: Intermittent starting
« Reply #1 on: January 17, 2025, 10:30:29 pm »
Oof. I mean you know me I've nothing useful to add. But it does (does it?) sound like there's bits jangling about when the starter is spinning... broken teeth? Are teeth involved?

Someone less millennial will be able to say but shouldn't we hear the thing turning over if the starter is spinning or is there a clutch somewhere? I'll realoem and educate myself in the morning!
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Offline andym2

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Re: Intermittent starting
« Reply #2 on: January 17, 2025, 10:31:06 pm »
Assuming the starter motor is bolted in properly, my guess would be either a missing a tooth on the starter idler gear or the overrun clutch is sticking. Unlike the bendix on an old British car you can't just give it a tap with a hammer. 

Offline Matt

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Re: Intermittent starting
« Reply #3 on: January 18, 2025, 09:01:17 am »
Well chatgpt agrees haha.

Quote
What to Do Next?
Try Jump-Starting with a Strong Battery → If this helps, the battery is suspect.
Check for Oil-Related Symptoms → If the issue worsens in cold conditions, consider an oil change.
If Problem Persists, the Starter Clutch / Sprag Clutch Likely Needs Replacement.
This is common in BMW K-series bikes and is a known failure point over time.
Replacing the sprag clutch requires removing the alternator cover, and on some models, splitting the case.

Final Thoughts
Since your starter motor is new, but the problem remains, the starter clutch (sprag clutch) is the most likely cause. Unfortunately, replacing it is a moderate-to-advanced mechanical job, and if you’re not comfortable doing it, it’s best handled by a BMW specialist.

Would you like a repair manual link or a video tutorial to help with the repair? 🚀

EDIT: Then it got confused trying to give tutorials etc so I reverted to using the internet manually.

This discussion on k-bikes is a little scare - so i say book the bugger in soon and use the big K!

EDIT 2: This discussion seems more positive and a happy ending!
« Last Edit: January 18, 2025, 09:12:13 am by Matt »
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Offline Phmode

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Re: Intermittent starting
« Reply #4 on: January 18, 2025, 05:43:01 pm »
The starter is spinning but the teeth on the  starter are not engaging with the flywheel. Show me a picture of the starter from Real OEM whatever (cos I'm idle).

If the solenoid (which is actuated by the key and then shoots real 12v power to the starter coils AND pre-engages the teeth on the dog with the teeth on the flywheel) is separate from (although bolted to) the starter itself, then when they changed the starter, did the solenoid get changed?

Some starter/solenoid units are integral (and therefore expensive to fix if only the solenoid goes pop), whereas others are separate units (and therefore cheaper to fix if the solenoid goes pop).

Simples!

Offline chriscanning

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Re: Intermittent starting
« Reply #5 on: January 18, 2025, 06:47:18 pm »
I have an intermittent problem with starting.

Listen to/watch the video:
www.poqit.com/starter_fail.mp4

It only does this once in a while - maybe every 5th / 10th time. Occasionally (as in the video case) it doesn't start several times in a row.

I took it into BMW to investigate, and they couldn't reproduce it.
I then took it out several times until it failed again and then took it back to BMW. They listend to it (it only failed for about 2 seconds on the BMEW NOG premises and then fired, but that convinced them to replace the starter motor, just before Christmas.

It's taken a while to get back out and ride due to weather, but now I find it's not fixed.

I know the first step is to take it back to BMW, but does anyone have any hints on what else might go wrong - since it's not the motor itself?
(Actually, the ideal first step is to break it permanently so it can be diagnosed properly, but whatever.)

Thanks in advance...

Can I digress? Sounds like you have the bike on some kind of BM maintenance thingy or is that me just reading wrong.


Offline richtea

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Re: Intermittent starting
« Reply #6 on: January 18, 2025, 07:31:59 pm »
This discussion on k-bikes is a little scare - so i say book the bugger in soon and use the big K!

EDIT 2: This discussion seems more positive and a happy ending!

Good searching, Matt. Thanks.

The first link is for a K1200RS, but according to this, the K1300S has a 'starter sprag gear':
https://www.k-bikes.com/threads/rebuilding-k1300s-engine-easier-than-youd-think.51708/

From the K1200RS link:
'Many metal fragments from the sprag were throughout the crankcase.'
Since the bike was also serviced and no mention if metal chunks came up, I thint I can tentatively discount that one. With fingers firmly crossed.

The second link is also a K1200RS, but that was solved by cleaning. That would be sweet. I will read further.

The starter is spinning but the teeth on the  starter are not engaging with the flywheel. Show me a picture of the starter from Real OEM whatever (cos I'm idle).

I can't find a suitable picture of the engine in RealOEM.com. This is the starter motor - probably not useful:
https://www.realoem.com/bmw/enUS/showparts?id=0508-EUR-09-2015-K40-BMW-K_1300_S_0508,0509_&diagId=12_1358

And this YouTube vid shows the position of the starter motor (between the tank and engine), and it's end:
https://youtu.be/Mq1uwLpJzE4?t=309

Can I digress? Sounds like you have the bike on some kind of BM maintenance thingy or is that me just reading wrong.

Correct - a 5 year/30k plan which was a proper bargain at £210 per service, inc the big ones.
But I cancelled the warranty unfortunately, in a fit of pique at Warwick Shytner doing such a sub-standard bodge job last year. Some you win, some you lose! Hey ho.

Offline chriscanning

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Re: Intermittent starting
« Reply #7 on: January 18, 2025, 08:14:34 pm »
Sensed their was something by the tone of your post and why the dealer took the easy way out cuz my gut says tooth off the starter wring which is going to be a major ball ache compared to putting a new starter in,although while looking at the easy options I’d also go lithium battery if you haven’t already.

Offline andym2

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Re: Intermittent starting
« Reply #8 on: January 18, 2025, 09:30:45 pm »
According to RepRom you get the idler gear out by removing the clutch basket then undoing the bolt on the end of a short shaft, and the starter free wheel is behind the alternator mounting.

https://ibb.co/5kb5nqB
https://ibb.co/fn3Hv5g

Hard to see exactly where this is from the diagrams, but a lot more disassembly to change either than just swapping a starter motor.

PS I've got a clutch holding tool if you need it.
« Last Edit: January 18, 2025, 09:39:21 pm by andym2 »

Offline Phmode

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Re: Intermittent starting
« Reply #9 on: January 18, 2025, 10:55:36 pm »
Ah Bugger! I forgot you threw a hissy fit. And no solenoid with a spray clutch.

So, seat off, tank shrouds off, tank out.

That gives you access to the starter motor. Disconnect cable, remove two bolts and starter motor comes out. 20 minutes so far...

That will let you see where the splined shaft on the end of the starter engages inside the transmission housing. That will show whether there is a damaged tooth somewhere. BUT...

When it spins over but doesn't start and then eventually it does, it 'can't' be a chipped/missing tooth otherwise it would never engage unless you moved the bike with it in gear to move the damaged tooth away from the splined shaft.

My money is now on the sprag clutch thingummy which is somewhere I have never been.

Offline richtea

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Re: Intermittent starting
« Reply #10 on: January 19, 2025, 06:16:47 pm »
When it spins over but doesn't start and then eventually it does, it 'can't' be a chipped/missing tooth otherwise it would never engage unless you moved the bike with it in gear to move the damaged tooth away from the splined shaft.

The annoyance is it often starts. Too often to ride to NOG on spec and guarantee I can demonstrate it (although I did manage it last time). And I never move the bike - well, not noticeably / on purpose - and it starts anyway, with no memorable change. I do try power off/on again, and the battery seems plenty strong enough. Still no real hints to the source of the problem.

But all good info, thanks!

I think I'll start with a call / visit to NOG before I stretch my mechanicing skills beyond their very small envelope.
« Last Edit: January 19, 2025, 08:19:04 pm by richtea »

Offline Grumpy jase

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Re: Intermittent starting
« Reply #11 on: January 20, 2025, 10:11:23 am »
Hi Rich, I'd say that is the sprag clutch.  I'd be wary of riding it much as if it lets go properly, it could disintegrate.  It sounds like it has partially failed, with some of the balls no longer intact, which is why it is intermittent. 
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Offline richtea

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Re: Intermittent starting
« Reply #12 on: January 20, 2025, 05:30:20 pm »
Thanks Jase. I will will ring NOG tomorrow, and ask for advice.