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Discussion Starter · #1 ·
Thanks for letting me vent....

I have a 2005 K12S w/ 27,000 miles on the clock. This spring, the engine developed the following symptoms: when fully warmed up (warm enough for the cooling fan to run) it runs on only 3 cylinders at RPM below ~3500. Above this RPM, all is good. When the engine is cold, it runs smoothly at low RPM. The bad news is that the techs couldn't find anything wrong and suggested that it seemed normal to them. The good news is that they charged me $0.00 for running the diagnostics and checking obvious potential explanations, e.g,. loose plug wires, etc.

Can anyone suggest what is going on? I know that rough idling is not uncommon for some K12S bikes, but temp-related changes in low RPM performance is new to me.

Thanks in advance,

Peterh
 

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Peterh said:
The good news is that they charged me $0.00 for running the diagnostics and checking obvious potential explanations, e.g,. loose plug wires, etc.

While your situation is not funny, I find the above statement is since the bike has no plug wires. :teeth


On a 2005 bike I would think bad coil as well. Unfortunately, a coil can measure OK when off the bike but not work well when actually in service. Also, they are expensive to replace just to check.

I would make sure it's only running on 3 cylinders. An easy way to do this is to put you hand on the exhaust pipes. If you don't leave pieces of melted flesh on one, it's probably not firing all the time.

But, it could be anything from the plugs, coils, crankshaft sensor, fuel pressure regulator, fuel pressure sensor, fuel injectors, fuel filter, etc.

This is where a true mechanic comes in handy. Not one that plugs it into a computer and says EVERYTHING's FINE. :wtf:
 

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JCW said:
While your situation is not funny, I find the above statement is since the bike has no plug wires. :teeth


On a 2005 bike I would think bad coil as well. Unfortunately, a coil can measure OK when off the bike but not work well when actually in service. Also, they are expensive to replace just to check.

I would make sure it's only running on 3 cylinders. An easy way to do this is to put you hand on the exhaust pipes. If you don't leave pieces of melted flesh on one, it's probably not firing all the time

snip
Well there are wires to the coils...
You might buy one of those IR temperature reading devices...Harbor Freight has them for less than 50 bucks and save the skin on your hands. They are really great for checking exh pipes.
 

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Intakes

I had a similar issue on my '05 K1200S: ran very rough at idle when engine was hot. I went through many of the same diagnostics, but in the end a simple cleaning of my intake air filters fixed the problem. They were caked with leaves, rocks, half a dead bird, etc (why BMW doesn't put screens over those gargantuan intake ports is beyond my comprehension).

I can only assume that for some reason, on my bike, the air pressure required at intake is greater when the engine is hot, which is why my clogged filters would manifest the problem only when engine was hot. I also had a thought that it might be related to the left intake being more clogged than the right one, and perhaps the bike favors the left intake at idle? All I do know is that the process of cleaning them out (whether it was intake obstruction or something else I accidentally fixed while pulling it all apart), fixed my problem. Good luck.

--
WarrenT
'05 K1200S
 

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Discussion Starter · #6 ·
simple fix

At the end of the day, it was a simple fix... Fifty miles w/ STP fuel system cleaner in the tank, and most of the symptoms went away.

cheers,
 
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If you can find it, BMW recommended Techron Concentrate (not the dilluted one) for the ailing 1300s that were stalling. Maybe the same stuff, but why not! Found it at Pep Boys and Advanced Auto Parts. Most auto parts places should have it.
 

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2012 BMW K1300S (also 1993 BMW R1100RS and 1974 BMW R60/6)
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Cross-posting K1300 R idle problem from other much more recent (though still pretty stale) discussion.

In short, a 2018 software version update MIGHT be the silver bullet.

Hope this helps.
 

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Are there software updates for the ’05 K1200s?
 
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