Stumbling and stuttering - K-Bikes.com - Excellence in Motion
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post #1 of 10 (permalink) Old May 11th, 2020, 10:05 pm Thread Starter
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Stumbling and stuttering

First thing I noticed about my '02 k12RS this morning is the clock had lost 4 hrs and 17 minutes since Friday. Thought it was curious, but then the engine stumbled and died when easing out the clutch in 1st. I had to nurse the throttle to get the bike moving but, after that, it was the usual joy to drive. After arriving at work, bike thoroughly warmed up, I snapped the throttle a few times and every time it stumbled like it wasn't getting enough fuel. I tried a quick open to half throttle and hold it there and the engine stumbled and protested up to 3k or so and smoothed out nicely and continued to rev higher until I released the throttle. It did that several times with no improvement. On the way home under load, acceleration is as strong and smooth as it ever was.

Other than the clock anomaly, the only things I've done recently are re-install the side panels and put 2 gallons of month old shell premium in the tank.

What does K-bikes think? Bad gas or something more sinister?
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post #2 of 10 (permalink) Old May 11th, 2020, 11:09 pm
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Start with the easy one. Your battery is probably almost dead. Stumbling while running can be a bad connection to the battery also. Take your volt meter and read the voltage while stopped. Keeping the meter connected start the bike and observe the voltage drop. If it goes below 9.5 the battery is no good. Be aware that stumbling in this bike can also be wire insulation on the Hall effect crank sensor.
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post #3 of 10 (permalink) Old May 12th, 2020, 5:08 am
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Yep battery a likely cause to investigate first. If you are removing/installing a battery be sure to remember there are TWO negative battery cables to attach. This is super important to remember. A TPS reset is good practice anytime your battery is disconnected for more than 20 minutes too. Other likely causes of cold stumbling, especially in cooler weather is an intake air leak, and the vacuum crankcase breather hose is a well known culprit to split/crack. If you have an excessive oily mess on top of the engine behind the throttle bodies this is a dead giveaway to investigate further.

2002 K1200RS Owned from new. Pacific Blue, Ohlins. 183,000kmís
2016 K1300R Black, Remus hexacone. 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #4 of 10 (permalink) Old May 12th, 2020, 8:03 am Thread Starter
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Ok, will check all of that but, bike has had a lot of maintenance work done over the past 12 months: new battery, new breather hose, fuel/air filter etc. Battery shows all the right signs when put on the trickle charger so we'll see. Will report back.
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post #5 of 10 (permalink) Old May 12th, 2020, 8:07 pm Thread Starter
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So, it isn't the battery. Cold static voltage was 12.2, dropped to 10.9 on start, then immediately to 13.5 post start, even with brakes, grip heaters and headlight on. Just for drill, I cleaned the terminals and wire connectors. Did the TPS reset. Sadly, it almost sounds worse but, I didn't give it much time to warm up. Symptoms are similar to the timing being retarded/not advancing or not getting enough fuel. So, I guess its on to the hall sensor. Where do I find it and how do I test it? I have the Clymer, but the index is not it's strong suite. Just point me to a page number. Thanks for all the help. Would have loved to see this go away with a new battery.
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post #6 of 10 (permalink) Old May 13th, 2020, 3:25 am
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Going back to your opening post, I keep looking at the part about your clock and can’t help thinking there is a connection here. Clearly the only way the clock could loose time is if it it looses power - positive or negative. By my own admission, electrical issues are not my strong point, however I think I’d investigate the earth connections and make sure they are all sound. The clock earths (according to Clymer) through the neutral switch and the side stand switch, and then appears to run through a diode before earthing through the clutch micro switch. It’s a disaster. I would start with checking all the wiring connectors on these circuits and make sure all the earths (brown) are solid. Make sure all the switches are clean of road grime etc. H96669 or Sailor should chime in on this but have been a little quiet lately. They have a huge wealth of knowledge.

2002 K1200RS Owned from new. Pacific Blue, Ohlins. 183,000kmís
2016 K1300R Black, Remus hexacone. 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #7 of 10 (permalink) Old May 13th, 2020, 7:07 pm Thread Starter
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And the winner is......

Flyingkiwi, who correctly guessed crankcase breather hose.

The clock thing, it turns out, was a red herring, so there is still an issue there somewhere. Regardless:

I was able to remove the panels again and poke around a bit looking for anything obvious before I started tearing into it in earnest. On taking a peek at the top of the engine, I happened to notice the breather manifold that connects the 4 intake tubes had slipped off the front 2 fittings. Tried to finesse it back into place, but I might have dislodged one of the back 2 as it still runs poorly. Last spring when I installed that thing, I had lowered the engine in support of a clutch rebuild. Am I going to have to lower the engine again just to fix this or can someone suggest an easier way?
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post #8 of 10 (permalink) Old May 13th, 2020, 11:57 pm
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You will be able to replace the breather hose without raising the frame. It’s a fiddly job but very doable all the same. I suggest you first clean the area as much as you possibly can, and working from top to bottom, remove the air box and throttle bodies, (remove the injectors before removing the TB’s) leaving all cables in place if you wish. Take heaps of photos, and even if your sure how it goes back, take the photos anyway - trust me on this. There are different fittings attaching the air intakes to the TB’s including (if you have cruise control) two non reusable clips that are in fact reusable. Clymer covers this pretty well so I won’t go into details here, suffice to say orientation and position of clamps is VERY important. I can help you with the re use of the clamps when you get to that point if needed. Under the manifold stubs which are attached to the engine block are O-rings which should be replaced since your nearly there anyway. When the stubs are off you will notice brass collars where the screws pass through, and after many years they start to sit a little proud of the plastic stub. Give these a hone with emory paper on a flat surface - glass is best here - until perfectly flat. Also check for corrosion on the engine block and attend to if necessary. Forward of the front intake is the water feed stub and this is also worth a good look since your this far in anyway. I’ll leave that to you, however there is an O-ring under it... Every second coolant change at four years I remove the radiators and all hoses for a thorough clean and inspection. Earlier on I mentioned removing the injectors. Perfect opportunity to have them professionally cleaned and flowed as dirty injectors cause poor idle and running. These are generic BMW injectors found on many of their cars so any injector business will deal with them, and of course they should fit new O- rings as part of the service. Give the TB’s a thorough clean, including the butterflies as they get pretty dirty too. Check the two screws holding each butterfly in place are secure and tight. Unusual for them to come loose, but it has happened. Probably missed something, but this will get you started and others will undoubtedly chime in with suggestions too. I’m a huge believer in preventative maintenance.

2002 K1200RS Owned from new. Pacific Blue, Ohlins. 183,000kmís
2016 K1300R Black, Remus hexacone. 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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post #9 of 10 (permalink) Old May 14th, 2020, 12:37 pm
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Here is a set of pliers that will help with those click hose clamps. They are definitely intended to be re used.
https://www.amazon.com/Pliers-Clic-R...s%2C226&sr=8-2
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post #10 of 10 (permalink) Old May 15th, 2020, 4:26 am
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Hey Beach thanks for sharing, I didnít know about the pliers and without them itís a bit of a lottery getting the clamps to go back together. I have found that manipulating the clamp into a closed position as much as possible before installation makes it possible to snap them back together with a pair of needle nose pliers, common in most peoples garage tool kit.

2002 K1200RS Owned from new. Pacific Blue, Ohlins. 183,000kmís
2016 K1300R Black, Remus hexacone. 6000kmís
The family history
1951 AJS 500 single - my Dads
1916 Triumph Type H, Western front, France WW1 - my Grandads
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