K1200S Stranded me; diagnosis suggestions? - K-Bikes.com - Excellence in Motion
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post #1 of 6 (permalink) Old Jun 17th, 2018, 1:03 pm Thread Starter
Dobervol's Avatar
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Question K1200S Stranded me; diagnosis suggestions?

’06 K12S, fairly new to me, no issues until yesterday on a drive way out in the TN twisties. Started noticing slight, quick off/on surge in gears 3-5 at about 6-7k rpm. Ride on about 15 miles, and it’s now in all gears and at nearly all rpm and getting worse. Bike dies the first time headed up the side of a mountain on switchbacks. Get it restarted several times and to top of mountain. Figure it might be one of the umpteen heat-related issues with this bike, since it’s the hottest day I’ve had the bike out yet. Wait 15-20 min. Still won’t start for more than a few seconds. Slowly coast 9 miles back down mountain (no servo issues with my bike at least, since I lived through the experience). Stop and start with at least 5 min. wait at least 10 more times, including having to push the bike out of several intersections (decided to go back home through civilization, in case I got in real trouble). Despite the ambient heat, however, water temp never gets any hotter than I've had it up to previously. Finally, battery dies, and that's it.

Possibly relevant info? BMW newer hydraulic cam chain tensioner installed (Abe Lincoln stovepipe hat). BoosterPlug installed (and routed to a suggested location, next to the right air snorkel; I never had the extent of stalling or surging or idling noise or other throttle issues some did, but put it on anyway. To be honest, never noticed any difference, better or worse, since installing it). Hottest and most humid day bike ridden so far, as mentioned above, and problem got worse as day got hotter. Only things done since last ride: top off with no ethanol gas, and throw in a can of the much beloved Liqui-Moly 4T racing fuel additive. In case one of those was the issue, I stopped at a gas station on the way back, and topped off again to dilute any ill effects of either the newer gas or additive, but it just kept getting worse. Dash never showed a code, until the engine actually stopped running, at which time I got the dreaded red triangle (well, thanks, bike; I kinda noticed you quit running!).

The way the engine was behaving, no way an injector was clogged, or spark plug had come loose. It feels like any spark and/or fueling issues were coming from the computer, not anything mechanical.

Am I stuck buying the Hex GS-911 to hope it will solve the mystery (I've seen a couple horror stories where it said all was well when it wasn't, even though the reviews are almost all positive), or anything else I might try or check which would be simple, or something I was too dumb to consider? Thanks in advance for any ideas or expertise, guys/gals.

EDIT: Just went down to the garage and...after Opti-mate back on all night and battery recovery, she started right up at first touch. Only abnormal thing was for less than a second, the cam chain sounded louder than ever before the fluid got in the tensioner (not merely loud, but like rocks-in-the-case loud), but went away a split second later and never returned. I let her run, repeatedly rolled on and off the throttle, held it at 4k for an extended period of time with no fueling glitches, and heated the water up to the same temp as when it just wouldn't go any further yesterday, and of course, everything ran just fine. Wut...the...fudge?

Last edited by Dobervol; Jun 17th, 2018 at 3:16 pm.
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post #2 of 6 (permalink) Old Jun 19th, 2018, 2:10 am
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Start the bike, measure the voltage on the battery while running. Could be a bad alternator which makes the system lack the power it need's to run all the electric's correctly.

You should be getting something between 13,8-14.1v with engine running and it charges as it should.
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post #3 of 6 (permalink) Old Jun 19th, 2018, 8:45 am Thread Starter
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Originally Posted by Mattias_r View Post
Start the bike, measure the voltage on the battery while running. Could be a bad alternator which makes the system lack the power it need's to run all the electric's correctly.

You should be getting something between 13,8-14.1v with engine running and it charges as it should.
Thanks for the idea. I can replace the alternator myself, but not the fuel pump (due to the huge metal ring which holds it in), which is another possible culprit.

EDIT: Alternator would be just as bad or worse, as BMW wants over $1K for a new one! Yeeeow! Didn't see that one coming. Makes a $500 fuel pump assy cheap by comparison, even though I'd still have the cost of install at the dealer on that one. If the main alternator needs replacing, I'd be riding my Yamaha until I could find one at salvage, or rebuilt.

Last edited by Dobervol; Jun 19th, 2018 at 8:54 am.
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post #4 of 6 (permalink) Old Jun 20th, 2018, 6:51 am
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Don't fret the alternator. There are tons available used for under the $60 range, and even reman ones available around $200. My guess would be the fuel pump as well though, as you mentioned everything was hot after the ride when it acted up. Also the pumps are dirt cheap, as you can change just the pump, not the whole assembly with an upgraded one, which may be good PM just in case.
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post #5 of 6 (permalink) Old Jun 25th, 2018, 8:32 am
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It sure sounds like your battery is not getting charged by the bike's charging system.

A good condition battery that has been discharged (i.e. lights left on) will often slowly recover enough to crank the vehicle, just like your's did, but is not getting charged so it runs down again.

It's probably something simple like a bad connection at a battery terminal, alternator or ground connection. Make sure they are clean and tight. A little corrosion from washing the bike or rain will make you crazy.

Check the voltage at the battery while the engine is running at about 2500 RPM. If you have an AGM type battery (Odyssey PC680 , WESTCO, etc "sealed") you need about 14.5-.7 Volts to fully charge it. Older lead-acid flooded plate batts need 13.5 Volts. Wiggle the connections while looking at the voltmeter to see if anything changes.

It might be something like a broken wire in the harness (hard to find). Older bikes like mine ('00 R1200RS) will not charge if the "ALT" light bulb on the dash burns out.

It could be a bad voltage regulator or a brush in the alt not making contact.

EME has alternators and replacement voltage regulators ($39 for my volt reg, with brushes): Motorcycle Parts: BMW, Moto Guzzi, Ducati. Many Brands in Stock. Bosch, Mahle, Valeo, EnDuraLast, NGK, NTK, Mann, Dynatek, Signal Dynamics, C-Tek, BMW, Ducati Energia, Duke Cannon, Sachse, Westco, Deka, Motorrad Elektrik, BERU, BMW and More...

Mine was easy to replace.

If you have an AGM battery and only 13.7 V, you might want to upgrade the voltage regulator to a 14.5 V. Ask Lori at EME, she is very good with this.

More info on AGM's here:Knowledge - AGM Battery Info - VDC Electronics

You would also want to make sure your maintenance charger at home is AGM rated.

Do some testing and report back on what you find.
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post #6 of 6 (permalink) Old Jun 7th, 2019, 7:49 am
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So did you figure this out? First thing I would have done is isolate the Boosterplug to see if that was a problem.
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