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Thread: 2012 R1200RT: can't get a good throttle body sync (paging JVB!)

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    2012 R1200RT: can't get a good throttle body sync (paging JVB!)

    Hey folks,

    I've read every thread under the sun on this, followed JVB's excellent video, and I think I have a pretty good handle on the mechanisms involved.

    However, I can't get a good TBS.

    Here's what I do:

    * Check free play. All cables seem to have adequate free play.
    * Loosen then re-snug right throttle body lock nut.
    * Calibrate Harmonizer.
    * Hold revs around 3200, adjust adjustment nut until zeroed.
    * Tighten down lock nut, fix adjustment to correct.

    Here's my issue: if I get a steady ~0 at 3200 with no load, my readings on the road range from low-+ve at crawling speeds, up to +70 if I'm holding a steady 4000rpm in 1st gear.

    There's some perceived vibration, particularly in the left grip, at 4k or above, which is encouraging me to shift early. I'm trying to fix that.

    (Last year's pre-trip sync was so bad that I stopped in a parking lot after 50 miles, pulled off all the plastic, and basically re-did the sync 'blind' -- I kept my gear on and relied on vibration feel on countless quick runs up and down the lot to get something bearable, mostly ignoring the output of the Harmonizer. I'd like to do better this year!)

    Baking in extra -ve during syncing drops the huge +ve offset when on the road, but I'm not feeling good about having an apparently miscalibrated machine in an attempt to correct a different situation. And that -ve offset seems to add some vibration to the footpegs.

    I feel like this shouldn't be as trial-and-error based as it seems to be: most other experiences seem to be "if it zeroes on the center stand, it'll be smooth sailing on the road". That's not my experience so far.


    The only things that I can observe are mechanically questionable are:

    * The top exhaust valve clearance on the throttle-side cylinder is slightly over 0.406mm. All other valve clearances are perfectly in-spec.
    * The secondary plugs were both fouled, mostly dry carbon, some oil on the clutch-side cylinder's secondary plug's threads. I chalk this up to short runs as I did diagnostic work prepping for spring.


    Can anyone suggest possible causes or things to try? Or is this a case of "take it to the dealer, let them try?" (it's under warranty until November, so if something's wrong it shouldn't cost me, but of course the service itself will).

    Thanks in advance, all.
    Last edited by holygoat; 03-17-2014 at 12:02 AM.

  2. #2
    Cam Killer marchyman's Avatar
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    What does the harmonizer show at idle? If you have greater than a 25 mbar imbalance then you MUST first fix that by getting your valves correct, making sure there are no air leaks, etc.

    I know everyone is keen on adjusting off idle at 3000 or 4000 RPM, but the butterflies are open enough then that you might not notice small changes. The reprom specified the off idle check at 1400-1800 RPM, i.e. throttle barely cracked. After you've done that adjustment make sure you still have free play all around. If you don't (and I've been there) you need to start over with more free play.

    And this should all be checked with the engine at normal operating temperature.

    If you have a GS-911 available resetting the steppers and parking the steppers before checking for idle can also sometimes be helpful.

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    Everything Marc told you is correct.

    You've got to get valves right to get a within spec idle vacuum that then allows you to do a synch at 1400-1800. (I check at higher revs also but its the lower rev is the high sensitivity point)

    Vacuum leaks are a common cause of problems and can be caused by something as simple as leaving off a nipple or a funky hose connection at the throttle body or in the canister vent system. Its always good to review who did what on the bike to anticipate where to look for such leaks.

    If you have GS-911 and know how to read real time engine log data that might give you an idea of what's causing your problem.

    Just remember the boxer isn't an in line 4...

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    Thanks for the replies!

    At idle, values are small (<8).

    With a sync to zero with revs anywhere above idle (i.e., not accounting for error under load -- a "normal" sync), there's plenty of free play.

    Engine is at normal operating temperature.

    The behavior I'm seeing seems to be a linear (or greater) relationship between engine RPM and pressure imbalance ? that is, at ~2000 rpm the Harmonizer claims the engine is pretty close to balanced (and I'm very happy with its smoothness around town, in the areas most people complain of vibration), but if I hold steady at 4000rpm under load the measurement is well off.

    That concerns me, because everything I've read suggests that it should be harder to maintain balance at low rpm, not high, especially at idle -- and thus the imbalance isn't down to the throttle bodies. In order to hit 0 at 4000rpm, it would seem that I need to shift the line on that imaginary graph down by a lot, which doesn't seem right.

    I'll check for any obvious hose/nipple errors, but I haven't noticed anything so far.

    Would a vacuum leak be increasingly more significant as revs increase?

    Is there a good technique for finding vacuum leaks at home?

    Would a coil issue result in this kind of symptom?

    Thanks again.

  5. #5
    Benchwrenching PGlaves's Avatar
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    vacuum leak distorting the synch down low - meaning the throttle plates aren't really equal angles, so at hiugher rpm the difference is magnified.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  6. #6
    Cam Killer marchyman's Avatar
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    In the bad old days I'd spray carb cleaner around the carb. If the RPM changed there was an air leak. Not sure carb cleaner is the safest thing to use with all the plastic/rubber bits around the throttle body.

    And let me throw out this hypothesis: you are checking the idle balance with the steppers engaged, correct. So the steppers could be doing their job well enough that they are removing a largish imbalance. Once you get off idle and the steppers stop doing their thing you'll get an imbalance. I think. I am not 100% sure that's how beemer engine management works.

    I'd try to borrow a GS-911 and use it to sync the steppers, then park them before checking idle balance. Again, I don't know that it will make a difference. My only experience is the opposite. The idle balance was once terrible on my '05 GS before syncing then parking the steppers. Most of the time it didn't make much of a difference either way.

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    If there is something wrong in your Bowden cable box you will never be able to get a sync to stick. I've gone through this with my Camhead. If your bike is under warranty, I'd give it to the dealer to look at it.

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    A bozo on the bus deilenberger's Avatar
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    I'd STRONGLY suggest reading the TB sync procedure in the DIY section of this forum.

    A few salient points:

    1 - Balance at idle is meaningless - the steppers are controlling the balance, the throttle plates are COMPLETELY closed (there is a step in the bore of the throttle body that seals them when the cable is slack.) ALL balance is being done by the steppers.

    2 - BOTH cables must have free play at idle.

    3 - It doesn't matter which side you adjust. Unlike the old oilheads - the throttle position sensor is "learned" by the BMSK and does not have to be any specific value to work correctly. I still do the starboard side since it's easier to reach the throttle on that side.

    4 - Balancing at 3,200 RPM is futile. Any imbalance will be most evident right off idle. The imbalance will be a larger part of the total airflow and will be more evident. I balance around 1,600 RPM, and no higher than 2,000 RPM.

    5 - The GS-911 is handy to lock the steppers - but once off idle - the steppers are put into lock-sync and are open the same number of steps. This is very easy to see with the GS-911 (which reads the position of the steppers continually.) The suggestion to disconnect them - is a bit bogus IMHO, since you don't know if they are in the same position (open the same amount) when you disconnect them. I'd suggest either locking them with the GS-911 (which first bottoms and calibrates the steps - then locks them in the same open position) - or simply counting on them being open the same amount above idle since they go into the lock-step mode.

    My experience is without an accurate valve adjustment (something that concerns me a bit with the camhead engine - which has discrete steps that the valves can only be adjusted in) - trying to balance the TB's may well make things worse rather than better. Since you know one valve IS out - would replacing the adjusting sphere bring it back closer to the other valves? If so - do so before trying to balance the TBs.

    My experience with the hexhead throttle-balance - is - it's almost never actually needed unless someone has "adjusted" it improperly. Once I get the valves adjusted correctly, my TB balance is typically perfect. I think BMW got the system bugs worked out with the hexhead. I assume they use the same cable system on the camheads.
    Don Eilenberger http://www.eilenberger.net
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    '07 R1200R (current ride) and some bimmers.. and a Porsche

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    One obvious thing to do here is get some other well experienced BMW R owner to ride your bike and see what he says. Some folks are inordinately sensitive to boxer vibes at 4000 or a bit better and never seem to get their bikes to suit them.

    You absolutely must have a good valve job (and at least on earlier models) an in spec end clearance (especially not too tight) on the rockers to get a decent balance.

    As usual Don is on target noting that boxer motors hold adjustment and synch for a very long time if done right. I haven't touched mine in so long I'd have to look up when- a bunch of miles and several years ago. Most who do their own work report similar experiences.

    I am not quite as worried about modest differences in valves of the newer motor (due to its stepwise method of setting) causing problems when they're all in spec though I would expect to be able to note modest differences. The reason is simple- cams don't generate much lift at all in the first few degrees of contact- which is all the difference there is unless a valve is way out spec- so air flow will be very close.

    Unless you know steppers are working well (and they sometimes mess up) it is good to shut the off with the GS-911 or even disconnect them doing a synch. Not sure if the GS-911 function would work properly with a stepper needing replacement. But steppers alone cannot cause the problem you note- thy don't have an impact on synch at recommended rpm.

    Vacuum leaks get found by the spray method- anything with an isobutane propellant in the can that won't eat your plastic or leave crap all over the bike that doesn't wipe off or evaporate is fine (eg don't use hair spray) as is any propelled organic solvent that burns and doesn't eat paint, rubber or plastic. When in doubt, test first...(If you can use it in the potato gun you should already own, its a candidate for testing)

    Could a funky coil cause your problem- yes. Would need to be a primary, probably. If your coils can throw a good spark over a 1/4"-3/8" gap they're probably OK- just checking with a grounded plug is worthless and it can take swaps with a known good coil to find a bad one. (No simple electronic tool for this though again GS-911 real time data may give you a clue. I cannot over emphasize the value of learning to read real time data on modern FI systems for troubleshooting many of those more obscure issues- it won't tell you to "Replace X" but if you understand, it provides great leads to track down. This skill is one of the differences between a competent modern wrench and parts swappers)

    You may be at the stage where a fresh set of experienced eyes is the fast way to end this.

    Many moons ago I noticed some vibes on a boxer I had just serviced and a quick look showed I had forgotten to replace the throttle body nipple on one side. I also learned that BMWs factory hoses don't fit those nipples at all well so I add zip ties to mine, snugged hard to keep them tight (my factory hoses even with a fresh cut end come off with just a couple lb pull- a sure sign they could easily generate a small leak though probably not enough to do what you describe).

    My R bike is a hexhead where you can seriously screw up synch by trying adjust those little brass screws that look like idle adjusters but aren't- they are factory set equalizers not meant to be disturbed. If your bike has similar- be sure to leave them alone.

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    May be easier to produce a time machine, go back to 2012 and hold back on the purchase of the Camhead, then buy a 2014 RT with fly by wire throttle . No more syncing with antiquated cables and screws needed. I know, I know, I'm not helping. Have you seen the new bike though ? Awesome !

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    If BMWs ride by wire isn't more reliable than its switches, that might not be a great idea.
    Waiting another 2-3 years to see what the real world says about the new one- I'm due 4 recall letters already, theoretically some time this year. Distance to dealer makes this a pita..

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    Thanks for the continued input, all. Before I start spraying flammable stuff around, I figured I'd inspect hoses. Can someone tell me if the left side intake should look like this? Because the right side doesn't.

    That's a thumbprint-sized, somewhat soft dip in the top of the hose.

    uploadfromtaptalk1395111557522.jpg

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    Quote Originally Posted by deilenberger View Post
    4 - Balancing at 3,200 RPM is futile. Any imbalance will be most evident right off idle. The imbalance will be a larger part of the total airflow and will be more evident. I balance around 1,600 RPM, and no higher than 2,000 RPM.
    The reason I attempted to balance at higher revs is because a balance at lower revs didn't seem to "stick" ? I got worse engine vibration at highway speeds. That seems to be evidence of a problem, rather than me just screwing up the balance!


    Quote Originally Posted by deilenberger View Post
    My experience is without an accurate valve adjustment (something that concerns me a bit with the camhead engine - which has discrete steps that the valves can only be adjusted in) - trying to balance the TB's may well make things worse rather than better. Since you know one valve IS out - would replacing the adjusting sphere bring it back closer to the other valves? If so - do so before trying to balance the TBs.
    Everything I've read suggests that such a small variation (probably 0.01 to 0.02mm) in the valve spec isn't worrisome, particularly if it's on the upper end rather than the lower end, and perhaps close enough to just be measurement error on my part. I'd welcome more informed points of view, though!

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    You don't even have a tool to measure .01 mm - that's .0004" and you couldn't set a valve that precisely with anything you own. It isn't easy to get them all within 3X that amount.

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    Quote Originally Posted by racer7 View Post
    You don't even have a tool to measure .01 mm - that's .0004" and you couldn't set a valve that precisely with anything you own. It isn't easy to get them all within 3X that amount.
    Yeah, that's why I'm not worried about it. The past-upper-limit feeler gauge fits, and the next one up doesn't. I could (and might) switch to the incrementally larger semisphere shim, but only if I (or the dealer) is already going in there.

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