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Stalling and stuttering

18K views 82 replies 11 participants last post by  Timskloss 
#1 ·
I have a 2010 F800ST that has recently (ever since the weather started getting warmer in the last 2-3 months) been giving me some low-RPM trouble.
First, it was problems taking off from a stop. I had to rev up to 2-3k, at least, to avoid stalling it. Just a few days ago, every time the RPM dropped (whether starting from 0 speed or during gear changes), the bike would hesitate as if it's going to stall before the revs pick up.
Per the extensive discussions on this forum about such issues, I have found that people usually suggest looking at:
- Idle actuator valve and/or the hoses from it
- Charcoal canister
- Fuel pump and possibly fuel controller (?)

Here what I've tried/checked so far:
1. Checked the battery - it's fine (battery tender shows more than 80% charged light when connected).
2. When taking off bodywork to check the idle actuator hoses (picture attached), I noticed that the coolant level in the overflow reservoir was lower than the min mark (I topped it off to close to max). The most recent case of RPM stuttering happened within 5 mins of starting the bike up (before the fan kicked on), so I'm assuming the coolant flow from the reservoir wouldn't have even started?
3. Checked idle actuator hoses by lightly pressing them near the bends (didn't seem cracked or overly soft). I didn't tinker with the charcoal canister circuit because I didn't have a replacement zip tie or the hose connectors required to bypass it.
4. Borrowed a wifi-based OBD tool (inexpensive one off of Amazon) from a friend to check for fault codes. Neither of us could get Motoscan to connect to it, but my friend used another app that he uses regularly with his car to check for them. It showed the idle RPM of my bike correctly and showed no fault codes. It does show fault codes when he connects it to his car.
5. Did the throttle reset cycle (5x twisting throttle from fully closed to fully open with the power on, etc.). Also tried revving the engine in neutral just after startup (i.e. not after full warmup/fan-on) - it revved up and went back to idle without any issues.

It's been at least 3-4 weeks since I rode the bike and maybe 1-2 months since I refueled, so could the charcoal canister could have dried out if it ever did get saturated (and therefore isn't the culprit)? Also, given there are no fault codes, does it mean the fuel pump/controller are OK? The previous owner said he had replaced it when the bike had trouble starting (I didn't ask when this happened). I also read conflicting reports (https://forums.bmwmoa.org/showthread.php?68499-Devilish-stalling-problem-2007-F800ST/page2) of whether or not fuel pump issues show fault codes. The engine does have that slow oil leak from up top (valve cover, I think), but there has never been an oil pressure light. I also checked the dipstick recently and the oil level is almost near max.

I'm just hoping to narrow down what the problem might be. Right now, the idle actuator hoses are about $55, the idle controller around $190, the fuel pump seems to be anywhere from $60-70 (non-OEM) to either $237 or $425, and God knows what other one-time use parts or unexpected extra parts I'll need to purchase as well. I definitely don't have the budget to test out all of them, and I'm starting to think about getting rid of the bike altogether. If you have any insights on how I can troubleshoot this issue, I would really appreciate them.
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#2 ·
Here's my humble opinion:

I don't think the vacuum hoses are the issue. The problem with these was that they were too soft and not pre-formed, so when they got hot, they could collapse on themselves restricting air flow. Your issue seems to not be when the engine is hot, so I doubt this is the problem. In case you want to rule this out on the cheap, then you can just replace them with standard fuel hose. That's what I did. The only down side is that they won't fit in the little plastic holders on the bottom of the air box, so I ran one of them outside the intake, and one of them between the intakes.

I also doubt that the idle actuator valve is the issue because if it was, then it wouldn't idle well and would probably stall instead of returning to idle after you revved it. Also, it sound like your symptoms occur as you are giving it throttle (taking off from a stop). This would require the butterfly valves to open as opposed to relying on the IAV to control air/fuel mix. Most IAV and vacuum hose problems caused a stall when you clutched in (like downshifting) after a fairly long consistent stretch. When the revs dropped, the IAV couldn't react quick enough to control air/fuel mixture after the butterfly valves closed. Then again, it looks like you already have the air box off, so you could go ahead and give it a good cleaning. While it's off, check all the other ports and rubber gasket where it attaches to the air box (there should be instructions for this in the hall of wisdom).

It sounds like a lack of fuel is the problem. If the charcoal filter is clogged, then I would again think that it would only give you problems after having ridden for a while because a plugged filter would create a vacuum in the fuel tank making it hard for the fuel pump. To test this (or a clogged roll over valve for that matter), you could open the gas cap when you are having the symptoms. If you hear it suck in air when you open it, then there is something clogged in one of the two vents (charcoal or roll over).

That leaves the fuel pump and/or controller. One of these two is my guess, but that's all it is... a guess. I don't know of any easy way to test pressure in the fuel lines or at the injectors. Which makes me think that the injectors could also be clogged. You could run some Techron through it. That certainly wouldn't hurt. Or for that matter, maybe there is a spark issue. Plugs and/or coils? They would probably give you more of a misfire or hesitation symptom though.

I know how frustrating this can be. I had stalling issues for a couple years until I finally got it sorted. For me it was a combo of IAV and throttle position sensor. I also added a BoosterPlug. Not sure how effective that is long term, but it smoothed things out for a while.

Keep us up to date on how it goes. Good luck!
 
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#3 ·
@Cramer, thank you for your inputs. I also feel that the problem is with the fuel/spark. I did have the airbox off, but I put everything back together since my bike is parked in the open.

I also like your ideas of Techron, fuel hose, and checking for vacuum inside the gas tank. I also ordered spark plugs and the ignition coil removal tool and will check that pathway. I used to have a Suzuki before this one, and when one of its spark plugs failed, the misfiring felt very similar (it's a loss of power, after all). The bike idled OK, but unlike the BMW, it stuttered consistently upon applying throttle (not just for a few seconds at low RPMs). Nevertheless, spark plugs aren't that expensive, and hopefully easy enough to replace.
I'm just wondering how I'll get the Techron to run sufficiently long through the whole fuel system since I'm worried about riding the bike right now. I guess I can just keep riding around the block.

Any chance you remember what diameter fuel hose you used for replacing the 2 IAV hoses? Also, what's the roll over valve, the one you said could also cause a tank vacuum if clogged?

I'm really hoping that it's not the fuel pump/controller. Since the FP controller is a pretty important module, won't that trigger the warning light on the dash? And one last question: if, by elimination, I do have to end up changing the fuel pump, would an aftermarket one like the ones from Amazon/eBay work OK? And do you have any recommendations for which one to get? (Sorry for making it a 2-part question)
 
#4 ·
The hose is 5/16 inch ID. Any auto parts store sells it in bulk for about $2 a foot. I bought 2 feet and trimmed it down to about 8-9 inches each. You don't need fuel injected line, just the standard will be plenty stiff, yet still flexible.

If you will be in there to swap plugs, you might as well remove the valve cover and fix that leak. If you do that you'll need a new gasket kit (very overpriced) and some red RTV for that corner where it's leaking. While you have the valve cover off you should also clean your secondary air system and check your valve clearances. Plus, having the valve cover off makes it a little easier to get to the plugs. A super thin and deep socket will also be necessary to reach them.

As for the techron, I'd try to get it to a highway and ride for a while with the revs up pretty high and do some WOT to get lots of fuel pushing through the injectors. That should help clear any possible deposits from the injectors. But, since you will be taking the air box off again anyway, you could actually remove the injectors and soak them instead.

The roll over valve is the part where the hose that goes to the charcoal filter enters the gas tank. There is a shiny little steel ball on the outside/top and 4 screws that hold it onto the tank. Take it off, remove the hose, and make sure that the ball inside there is loose enough to move when you tilt it. The idea is when the bike is on its side, the ball will seal the vent so that no gas will leak out. I think this vent and the charcoal filter are only on US bikes.

I've heard that the fuel pump is a pretty standard part. I wanna say it was the same as a Toyota corolla or something. So yes, I would think the ones from Amazon/eBay will be fine. You could also consider ebay for a used original part, but who knows how many miles or the condition. Either way, make sure you clean the fuel filter while you are at it. The easiest way is to pull it off, let it dry, then vacuum it clean. Careful putting the pump back in, I took mine out once to fix a fuel gauge problem and didn't seat it perfectly which led to a very big (and embarrassing) spill at the pump.

I hope you have a shop manual because you're getting into some fairly serious stuff here.
 
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#6 ·
I wouldn't be pointing fingers at any one issue being the most likely as your problem seems a bit unusual.

Start simple. If your plugs or air filter are old then replace those first. My next guess would be either the IAV or fuel pump/filter/tank vacuum. Contrary to logic, the idle controller works up to about 2000RPM (in other words, even when the throttle bodies are cracked slightly open). It's not a 0-1 operation but rather a gradual, complementary setup for low RPM control.

Your idle hoses are ok if they're not cracked, no point in replacing them. You should remove them and check for cracks properly. Clean your throttle bodies and the idle actuator when you replace the plugs.

No faults shown with a generic car app doesn't necessarily mean there really are none. Nevertheless, most fault codes on these bikes are from faulty sensors or various ECUs. I don't think a pump or pump controller failure would show up.
 
#7 ·
Hi. Here's my penny worth. I agree with Bachu, start simple. You say your bike is standing outside and you haven't ridden it for a while. Are you sure your fuel is ok? Could water have got in there? How old is the fuel? Just a couple of simple things to start with before considering big bucks. Rob.
 
#8 ·
This thread reminds me of the time my Chief Clerk (When in the Army) who had bought a large unreliable Fiat. He consulted me on a wide range of problems which cost a lot to rectify. After some time I realised he wasn't asking me for help. I asked him if at last it was running well. His reply was that it was worse than ever, but the RSM's suggestions were cheaper.[eek]
 
#9 ·
@Cramer and @Robert: I finally got some time to take a shot at checking some things off the list. Here's an interim update.
I got down to the ignition coils, but couldn't get to the spark plugs themselves. I underestimated how narrow the opening was, so the sockets I had from another (Suzuki GSX650F) toolkit weren't able to go all the way. They're the swiveling type and the hinge is what gets in the way. So I'll try to acquire a thin(ner) socket and try again. On my way there, I noticed a few things, one of which is completely unrelated to my current problem but has caused quite a bit of concern nonetheless.

Pics here:

1. There was oil ON TOP of the valve cover itself (pics 1 and 2). The left ignition coil had a little bit of oil near the top. The right coil had more, mostly near the bottom (pics 3-6). I checked the spark plugs by gently prodding them with a screwdriver and they seemed to be tight enough i.e. no play, I think. Unfortunately, I couldn't reach them with a socket.

2. The top (green) face of the idle actuator had a little bit of oily dirt, but I don't think that's significant. I didn't check its operation. The idle actuator hoses seemed fine - no cracks or very soft/weak spots anywhere. The engine breather hose and the secondary valve hose (that goes into the IAV) were also OK. A little bit of oil in the hose that goes from the reed valve (the silver part between the ignition coils in pics 1 & 2) to the secondary air valve, but that's exactly what that's supposed to be, I'm assuming.

3. Lastly, the unrelated yet concerning bit: the crack in the plastic cowl thingy (last 2 pics). I somehow hadn't noticed it so far. I tried gently wriggling the whole part and it didn't seem weak, but I'm sure that's super-expensive and super-painful to replace. How bad is that? Surprisingly, the bolt seems perfectly OK, so I'm wondering how it got broken. Can I just put some thread-lock or something similar that works with plastics and zip-tie it to the frame around it to act as a clamp and also a long-term stabilizer?

I wiped off the oil on top of the valve cover, from the ignition coils, and from the ignition coil openings in the valve cover. I'm not sure how oil got on the valve cover (accidental leaks from the hoses?) but I'm assuming it's not very serious since it's not a lot. Same with the ignition coil.

Also, excuse the verbosity of my posts. I'm trying to minimize the number of replies and be a little more verbose so it'll be easier to read should anyone need it in the future. If you have any corrections or proper part names for those I described poorly, please post them so that those keywords show up in forum searches. And as always, thank you for all your replies. I've just not been able to do much in the last week, so I'll post another update once I make progress.
 
#10 ·
I'm not a mechanic, but that "plastic cowl thingy" is a bit discerning. Although it appears to just supports the fairing, so I'd put some plastic epoxy in there and not worry about it.

The oil on the valve cover and coils is also not worth worrying about. If you have a more significant leak down the left front, then that's different and worth opening up the valve cover to fix. What I see is very little in volume, although it had to have been in aerosol form to coat everything like that. I don't know where it would have come from.

As you learned, you need a really skinny socket to get the spark plugs out. I've found that a Chinese made no-name deep socket set works perfectly.

As far as the idle air thingy (verbosity): The key is to clean it on the sides of the plunger and the threads of what drives the plunger in and out. These areas were not shown in your pics. Check this out for reference: https://f800riders.org/forum/showth...Idle-Actuator-Air-Bleed-Circuit#/topics/50935

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#11 ·
16mm Spark plug socket and 2 socket extensions + a 1/4" wrench and you'll get the spark plugs out.

The oil on the cover, I'd check the hose going out from the middle of the valve cover. That's a breather hose going to the airbox and it contains a bit of oil. A crack in it or too loose a fit on the valve cover could cause an oil spray. Other than that, the valve cover bolts could have faulty seals. No other oil sources above the cover.

Clean the idle motor and replace the plugs.

The crack you have is a bit troubling. You can look for a 2nd hand front support. They sometimes pop up at reasonable prices. Otherwise I'd think about getting it plastic welded by someone. Thankfully there are 3 other big bolts that keep it in place so you should be ok for the time being. All in all, it's a crucial part. This plastic piece is the "front" frame that supports: headlight assembly, front upper fairing, mirrors (though this I think is threaded to the headlight assembly) and the instrument cluster.
 
#12 ·
All sound advice from bachu. There shouldn't be any oil sitting on top of the valve cover. The reed valve (in the center) may be the source of the oil or it could have been a loosely coupled breather hose. Definitely inspect the source of that spray. In terms of your low RPM issues, it points to a possibly weak spark.

If new plugs don't cut it and you've looked at your vacuum hoses, my bet would be that one or both of your stick coils is going bad.
 
#13 · (Edited)
@ Cramer, Robert and rtully: I changed the spark plugs and cleaned the idle actuator a little bit. I didn't completely disassemble it coz I was a little scared about resisting the movement of the plunger (as suggested in Mokkybear's thread) and also about resting the battery on the valve cover. I checked the idle actuator and secondary air hoses but didn't replace them because they weren't cracked or weak anywhere. Also checked the engine breather hose and the reed valve hose; they were both very dry.
There was a lot of oil on the threads of the right spark plug and the left one wasn't fully torqued (wasn't loose, but started loosening easier than the right one). I'm guessing the oil on the spark plug thread is because of the valve cover gasket as well.
Images:

The problem still persists. I rode it around my block today, and sure enough, on the second loop, the bike stalled several times when I tried to get moving from a stop. I also took a video of the idling after warm-up (). Towards the end of the video, you can hear fluctuations in the idle. I used to have an I-4 bike before, so I don't know if I'm reading too much into a 2-cylinder's sound, but the idle seems more bassy/lanwmower-ish to me. I'm unable to recall how different it used to sound earlier when there weren't these stalling problems. I did smell a little bit of gas when I was standing behind the bike, but I guess that's not unusual at semi-warm idle?

I think my next steps are going to be:
- idle actuator disassembly and thorough cleaning as per the thread Cramer shared.
- ignition coil testing (if that's even possible by myself).
- changing the idle actuator hoses for good measure.
- changing the valve cover gasket because it seems to be causing a lot of annoying messes. It doesn't seem to be causing any of the problems I'm experiencing, though, so I'll prioritize this lower.

One question I had was, the OEM valve cover gasket set has new bolts and washers. How crucial is it to replace them, especially bolts? Would it be possible to replace the washers with hardware store ones?

Suggestions, comments, analyses welcome.
 
#16 ·
I think my next steps are going to be:
- ignition coil testing (if that's even possible by myself).
- changing the valve cover gasket because it seems to be causing a lot of annoying messes. It doesn't seem to be causing any of the problems I'm experiencing, though, so I'll prioritize this lower.

Suggestions, comments, analyses welcome.
Coil Test
The only test I am aware of on these coils is a resistance test (from the positive pin to the output). You'd have to research the expected resistance (I couldn't find a precise one in.a short google search which only generalized the expected resistance). However, coils often start to weaken as they heat up so a cold resistance test may not show an issue. They are not cheap to replace ($150 each) so I'd do this as a last resort.

From the oily plug, I'd bet your leak is in the spark plug well itself. There is a gasket that is replaced on the underside of the valve cover that may be worn or may not have been seated properly (most likely).

I've used the kit from euromotoelectrics.com (Denver) and their stick coils with very good success. $110 for the whole gasket kit https://www.euromotoelectrics.com/product-p/gsk-vcsetfplus.htm or you can just buy the bits you need.
 
#14 ·
Your idle in the video sounds smoother than mine. Nothing to worry about there. Every time you go to start it, you are supposed to wait until the orange light goes off in the dash so that the computer gets a chance to do its thing to prep the engine to start. I can't imagine that makes a huge difference, but I have read that and heard service tech's say it.

Changing the valve cover would be a great move, especially after seeing that oily plug. The bolt gaskets are more like rubber grommets if I remember right. I think all these gaskets are rubber. The only one you really need is the main one around the outside of the head and valve cover. The rest just come in the kit, and i think you can buy the big one separate. Remember that you will need additional RTV sealant on the left front corner. While you have it off, you should remove the secondary air reed valve and clean it up. You'd be amazed at how that will help with burbling and pops on deceleration. I think i mentioned it before, but since you will have the cover off, buy some feeler gauges and check valve clearances.
 
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#15 ·
If the hoses were ok then there's no point in changing them.

I'd start with replacing the valve cover gaskets as the oily spark plugs are a bit of a worry. Shine a light into the throttle bodies in a fully open position and check if there isn't a valve with a leaking seal. That's one other source of oil residue on spark plugs.

It's possible you have a failed spark plug valve cover seal. There's a big seal that goes around the valve cover itself and 2 small seals for the spark plug wells. When manipulating the valve cover remember that there's a small lip seal at the water pump end of the intake camshaft.

The valve cover bolts have rubber grommets, indeed. If they look ok, no need to replace them.

How's the idle RPM? Does it fluctuate? What's the mileage? When was the last valve check? What's the condition of the air filter?

Have you checked tank vacuum? Maybe try riding with the fuel cap open?
 
#17 ·
I tried riding with the fuel cap open and did a few throttle blips to around 2k-2.5k. No dice. Still Stalls. When I blipped the throttle, it stalled once but did OK the other 4-5 times, although the speed dropped a little below idle before recovering.
Before the problem, the mileage was pretty great. I can't come up with an exact number, but the instantaneous MPG values used to go as high as 71 when doing 45-50 in 6th gear. That's part of the reason why I refueled very sparingly, although I don't think fuel should go bad 1-2 months (to answer someone's suggestion higher up in the thread to check if fuel might be bad).
Don't know when the last valve clearance check was. Air filter seems OK - kind of yellowed on the filter-out side, not excessively dirty on the intake side. I forgot to check for oil by opening the throttle valves, but I'll do it soon when I replace the clamp (read below).

I cleaned the idle actuator by disassembling it. I reassembled it and I think I got it to its proper position when compared with my previous pictures. When I turn the key on, the top surface of the plunger goes about 2mm below the green gasket. Some pictures here:
I didn't ride it yet (after the cleaning) because I got fed up with the engine breather hose clamp. I've decided to replace it with one of those ratcheting clamps that can be tightened with a socket, as Robert mentioned in another thread. I'll post an update after replacing that clamp and riding it again.

I'm going to order the valve cover gasket and the water pump seal. I took off one of the valve cover bolts (the right side one below the ignition coil) to check how the rubber grommet is. The grommet was fine, but I realized that the metal washer and the grommet are held to the bolt head with another little metal flange. So the cleanest way to replace the washer/grommet would be to the replace the bolts as well. I feel like bolts that torque to 10 Nm don't need to be replaced, especially since I'll be using the RTV stuff.

Few questions about the valve cover gasket job:
1. what all do I need to remove to replace the valve cover gasket? The manual talks about removing radiator heat shield(s). Is that the black plastic cover towards the front of the bike that the engine breather hose and the secondary air hose are touching (pic 4 in the link above)?
2. Did you guys use the Permatex high tack kind of stuff to stick the gasket in place? I'm planning to get the Permatex ultra black because of the oil resistance. Should I also get this one?
3. Can I do the valve clearance check without a center stand? I have the center stand parts, but it was lower on my list of things to do. My bike is also lowered, so I wasn't sure if it'd get up on the stand.

@rtully, I will try to test the coils later. The manual suggests a spark gap tester tool in addition to the resistance check as you mentioned.
If I understand how the ignition system works correctly, the problem isn't with the coil/plug because their deterioration should cause consistent problems and not just at some RPMs or RPM transients, right? Same with air filter - I feel like a dirty filter would reduce power but not cause problems intermittently. Since the idle actuator seems to be clean enough and working OK, I'm kinda lost now since that was my prime suspect given all the threads on the forum here. I guess it leaves only fuel pump on the list of things to check, although I don't know how to test that without replacing it.
 
#18 ·
Few questions about the valve cover gasket job:
1. what all do I need to remove to replace the valve cover gasket? The manual talks about removing radiator heat shield(s). Is that the black plastic cover towards the front of the bike that the engine breather hose and the secondary air hose are touching (pic 4 in the link above)?
If I recall correctly, you do need to remove that shield to give you the clearance you need to work with the valve cover. That is the correct reference in your pic. I think I was able to loosen and move mine out of the way without taking it off the bike but I am not 100% sure.

2. Did you guys use the Permatex high tack kind of stuff to stick the gasket in place? I'm planning to get the Permatex ultra black because of the oil resistance. Should I also get this one?
I think I used red Permatex (regular RTV, not high tack). You don't need very much of it as I recall, just around the circular portion of the gasket according to the manual. One tip (mistake I made), the tight clearance when working makes it easy to accidentally pinch some of the wiring under the gasket. Did that to my F800GS without noticing.

3. Can I do the valve clearance check without a center stand? I have the center stand parts, but it was lower on my list of things to do. My bike is also lowered, so I wasn't sure if it'd get up on the stand.
You probably could but it would be painful. Getting the rear wheel up definitely makes things easier.

@rtully, I will try to test the coils later. The manual suggests a spark gap tester tool in addition to the resistance check as you mentioned.
If I understand how the ignition system works correctly, the problem isn't with the coil/plug because their deterioration should cause consistent problems and not just at some RPMs or RPM transients, right? I guess it leaves only fuel pump on the list of things to check, although I don't know how to test that without replacing it.
On my twin spark RT, one of my primary coils caused issues at low RPM only as the other cylinder and spark would compensate for it at higher RPMs so it is possible that a coil could be acting up this way on a twin cylinder bike.

The fuel pump, if it were weak, would likely cause issues at higher RPM (more demand for fuel) so I don't suspect it with your symptoms. I do wonder, however, about the possibility of a bad throttle position sensor. Maybe see if you can test that while you are in there?
 
#19 ·
2. The ultra black should be fine. Here's a copy/paste from their Amazon description:

Temperature Range -65°F to 500°F (-54°C to 260°C) intermittent
Suggested Applications: Valve covers, oil pans, intake manifold end seals, timing covers, and differential covers

3. If your bike is too low to get onto the center stand easily (after you've installed it, of course), try placing a 3/4" - 1" wood plank or something similar behind your back wheel, and roll the bike onto it. It will provide a bit more leverage for getting the bike on the stand.
 
#22 ·
Interim update before Valve Cover Gasket change - I tested it today after the Idle Actuator Valve cleaning 3 days ago and there's no change.
@rtully that ignition coil issue is interesting. Didn't think about that. I think you might be on to something w.r.t. Throttle Position Sensor, so I've definitely added it to my list. I'm hoping it's either an ignition coil or the TPS coz I want to ride, and also hoping it's neither of them coz they're super expensive (although I seem to have ruled out most of the cheap parts as culprits). I also bought a spark tester to test the coils that way. So I'm looking at a pretty hefty work day soon.

@Robert: The manual suggests something similar w.r.t. turning the engine - the bolt under the alternator cover. I couldn't find replacement alternator cover gaskets anywhere, so I was hesitant to take that approach. I'm not sure why the gasket is needed, though, because there doesn't seem to be any fluid or high pressure underneath.
I just checked the center stand position on my bike and I understand what you mean about the clearances. Maybe I'll install it just for the valve clearances and remove it again. Also, air filter pictures here.

@Rod and Ken, I didn't think about that. Love the simple idea. Hopefully I can pull it off that way.
 
#25 ·
Interim update before Valve Cover Gasket change - I tested it today after the Idle Actuator Valve cleaning 3 days ago and there's no change.
@rtully that ignition coil issue is interesting. Didn't think about that. I think you might be on to something w.r.t. Throttle Position Sensor,
Thinking about it a bit more, I'd make the TPS my next focal point. As per Cramer's experience, It could be the root cause.
 
#23 ·
The air filter seems ok but it's more important what it looks like between the fins.

Myself I'd consider used parts as for the price of one new TPS sensor you could buy anywhere between 5 and 10 used ones. Even with used parts, chasing stalling and idle gremlins on these bikes can get expensive quickly. Maybe think about a shop that has some good experience with these bikes. There are 2 things I'd consider buying new - idle motor and gear sensor.

Myself I've swapped out a ton of parts on my 2006 and never cured my hunting low RPM behaviour. By now I'm starting to think it's more due to the lack of catalytic converter on the Akrapovic exhaust. Almost won a Power Commander to check different fueling scenarios but the price got a little too high for me.

As for your problem, a possible culprit could still be the idle motor or pretty much any valve or sensor involved in air and fuel mixture delivery. These bikes are extremely sensitive to anything going wrong in these areas.

Regarding valve check. Rotating the engine DOES NOT require removal of any other covers other than the valve one. There is no need to remove the alternator cover for anything relating the valve job. There is a locator screw for TDC which is located on the clutch side. If you were to adjust the valves you need to screw in a special screw to lock the bike in TDC. Alternatively, if you can get the rear wheel up in the air, you can leave the TDC unlocked and simply rotate the engine back to TDC if it somehow moves, before refitting the cams.

If you do remove any of the side covers, the new gasket is necessary as the old one will be damaged during the removal. Alternatively you can use silicone sealant but anyone doing the job later on will curse you.

Attached is the image of the "nut" on the camshaft that allows for engine turning during a valve check.
 

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#24 ·
I had similar symptoms a couple years ago and after chasing a bunch of leads like you are, I swapped out the TPS with a used one. Thankfully it is a very generic part across many BMW models, so it was inexpensive and easy to find on eBay. Thankfully it solved my problem. Before replacing it would only start and run while I had the throttle open a little bit, and would die everyone I pulled the clutch in for enough time for the engine to come to idle. I did the reset procedure and it would fix things for a few minutes, but then back to stalling.

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#26 ·
I tested the TPS by measuring its resistance while opening and closing the throttle and took pictures of the intake valves by opening the throttle bodies: video and pics here. The intake vales seem to be OK.
According to the test description in the Haynes manual, the TPS seems to be fine, right? Although when I release it quickly (a click can be heard in the video when I do this), it does show 'open load' for a second before showing the higher resistance values.

I tried testing the ignition coils, but my multimeter probes have a lip that prevents them from fully going inside the coil on the spark plug end. I also couldn't simultaneously contact the 1 & 3 terminals because of how wide the multimeter probes were. The inline spark tester I bought was too long - after connecting one end to the spark plug and the other to the ignition coil, I couldn't plug in the ignition coil connector. I briefly considered doing the other test the Haynes manual recommends, i.e. pulling the coil out, connecting a spare spark plug to it, touching the spark plug threads to engine/ground and cranking, to see how the sparks look. This essentially means that I have to remount the airbox, connect the battery, and give it a try. I didn't have enough time, but I was also a little apprehensive because the threads don't contact the frame easily. I didn't wanna rush through what seems like a burn/electrocution hazard. Have any of you ever tried this kind of test?

Also, if the TPS is indeed OK, I'm back to square 1 and I don't know what to test next. I do have a fuel pump with the silver controller. I read the threads here about problems with that type, but my symptoms don't seem to match the ones in those threads.
 
#27 ·
When I had TPS issues, I couldn't find anything wrong when I tried testing it. The resistance varied as it moved. I think the problem was that it was a little off at the bottom of its range so when the throttle was closed, it sent a signal to the computer that was either beyond closed, or not quite closed (I don't know which) but it didn't tell the idle control air valve to do its job when the butterfly valves closed, so it would stall. At anything above 2500 RPM it ran fine. When I did the throttle open, throttle closed reset, it would work for a little bit. I guess the reset would tell the computer where in the potentiometer the bottom was when I closed the throttle. I must have had a short in that area of it.

As for your coils questions, I can't help. The only issue I've ever seen on motorcycles (or cars) related to coils was that they had come loose. A little antiseize fixed them up. But again, the symptoms in those cases were more of a misfire or hesitance nature as opposed to stalling and not idleing.

I really think it's worth getting a used TPS. They're easy to install because you can get it off without removing the fuel injection rail.

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#28 ·
I was thinking about getting a used one, too. I see some on eBay for around $50-60. The only question I had about installing a new one was whether it would need calibration from a BMW dealership. The Haynes manual says so, and it'll be very hard to ride it to the nearest service/dealership with this problem. Did you take it to the dealership, or just do the key on and 5x open/close routine?

I will try to muster some courage, maybe get and put on some mechanics gloves and test the ignition coils as well, just to rule them out.
 
#31 ·
I was thinking about getting a used one, too. I see some on eBay for around $50-60. The only question I had about installing a new one was whether it would need calibration from a BMW dealership.
I can't recall if the GS-911 does a TPS calibration. I was working on an '07 ST yesterday to solve an unstable idle and a dead stator replacement. I ended up replacing the idle actuator with a used one. The GS-911 does do a calibration of that and I know it does a reset of all the adaptations (thats the term used for the self-learning/self-calibrating). I think the TPS will self-calibrate with the procedure noted above.
 
#29 ·
The valves look ok, far as I can tell. When you're in there, might as well wipe the throttle bodies reasonably clean (the black residue around the plates).

It's probably a good idea to calibrate the TPS but the bike should work ok even without that. Certainly should be good enough to drive to get the "new" sensor calibrated. Speaking from experience, I have done the swap more than once.
 
#30 ·
When I swapped out my TPS for a used one I just did the throttle open/closed 5x thing and it's been great ever since. I bought it for about $50 from eBay which came off an R1200GS. Same part number.

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