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Thread: 2005 R1200ST complete loss of power when revs to full throttle

  1. #1
    Registered User landev's Avatar
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    2005 R1200ST complete loss of power when revs to full throttle

    Greetings,

    I picked up a "project" bike a couple of months ago, 2005 R1200ST with very low miles that had sat for ~ 3 years, same gas, gooey oil, lots of cracked rubber. There were some open recalls, most pertinent to this issue was the fuel pump.

    I drained the tank, put on a new fuel filter and rode it to a dealership ~ 90 miles north. It coughed and sputtered a bit before and after the recall service. (new fuel pump, banjo bolts, wheel flange, etc..) I have since adjusted the valves, new plugs, synced the TBs, new oil/filter, new air filter. The bike is running much better, but still has an issue when you blip the throttle. It feels like goosing the throttle shuts of the fuel supply until I release the throttle and things return to normal. I can throttle the bike hard (as long as it's a gradual increase) and it runs fine... actually it runs very strong. The loss of power is consistent however and happens EVERY time I goose the throttle. Seems if it were a fuel issue, it would stumble regardless of the rate of loading.

    I've come down to the idea that it's either a bad coil or fuel pressure regulator. When I did the throttle body sync, the GS911 showed me that cylinder temps were within .5 degree temp of each other. As I understand it, a bad coil would result in cooler temp on the bad coil side. Dunno. Primary resistance on all coils is between 1 and 1.5 ohm.

    This certainly "feels" like an electrical issue, but I'm still mystified about the feeling that it's just got either not enough fuel or too much. I'm now on my 3rd tank of fuel (with Seafoam) since draining the crap out of it. I also should mention that the injectors seem to have consistent patterns from one side to the other.

    Any ideas on this? Do I just need to run a few more tanks of fuel and see what happens?

    Thanks in advance!

    -l-

  2. #2
    Registered User GTRider's Avatar
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    A loss of power on sudden opening of throttle sounds like the bike is momentarily going lean. Were the blue paint marks on the TBs intact when you got the bike? If so, assuming the new plugs are to spec and the fuel pump/filter are new, Id be tempted to run a couple more tanks of fuel through it before tearing into the fuel rail and such. Id also recommend trying some BG-44 or Techron Fuel System Cleaner (not injector cleaner) in those tanks of fuel.

    Best,
    DeVern
    DGerber
    1983 R80ST 1984 R80 G/S-PD 2010 K1300GT 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  3. #3
    Registered User landev's Avatar
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    Thanks for that! Your advice is along my feeling of the issue. I wouldn't have thought of it being a "running lean" issue, but I am a self taught struggling mechanic.

    I ran the bike this afternoon... thought it was pretty much up to snuff as there was no longer coughing and sputtering for the first 28 miles... it was responding very strongly to throttle. It did start acting up again once I started on a twisty grade (fuel demand) and was totally bogged going into the first corner.

    It doesn't look like anyone's been monkeying about with the TB screws. As near as I can tell, the bike's never had much attention since it was new. The engine oil was like lavender black cream and what was in the fuel tank smelled more like lacquer thinner than petrol. I did check the spray pattern of the injectors this morning before I rode... they looked good.

    The odometer is on the fritz as the Motoronic shows 1.667 million km and the instrument cluster is pitching a fit about the erroneous reading. As the tires seemed to be original (factory 5gm BMW branded wheel weights) I'm guessing the bike has < 10K miles on it.

    It does seem like a fuel system issue, but I've no experience with complete shutdown of power at full throttle. I'm inclined to follow your advice and just run some more fuel + additive through it. It really runs much better than when I first started on this project. To me, that hints at gumming that needs to just be run out. Hopefully this makes sense!

    Thank you for your advice!

    -l-

  4. #4
    Registered User GTRider's Avatar
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    Ok, the blue-painted stop screws on the TBs are factory set, so the only two adjustment points for TB balance are the big brass screws and the cable ferrules. If your Motronic is throwing erroneous readings then you may want to check battery condition, clean the contacts on connectors (especially on the Motronic) and inspect for any wiring that may have degraded or been chewed by rodents.

    Best,
    DeVern
    DGerber
    1983 R80ST 1984 R80 G/S-PD 2010 K1300GT 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  5. #5
    Registered User landev's Avatar
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    Thanks! It seems like the throttle bodies are fairly untouched. I adjusted the play in the cables (by feel... didn't know how to physically measure them) before syncing them via my Carbmate. That was a bit of a chore, as I didn't realize I had to use the GS911 to lock the idle actuators before hand. I fooled with that for a good hour before realizing the correct procedure! My 2002 RS adjustment was much more straightforward... no intervening bits between the computer. I learn, albeit slowly!

    The service records on this bike show that it had an odometer issue in 2006... probably less than a year into it's life. The odo showed 9999999 and the shop that tinkered with it reported putting in a new circuit board. What that means is beyond me! My instinct is that when the "circuit board" work was performed, the Motoronic went bananas... perhaps from some static discharge? I don't think the bike has been worked on since then... just by the looks of things. The odo still reads 9999999 and the error code from the instrument cluster basically give the WTF error. "We don't know how to show anything above 1 mega miles!"

    The battery is relatively new and my Midtronics analyzer shows it to be good. When I took the bike for the recall work, the tech there logged the issue with BMW in hopes of some inkling as to what to do the the Motoronic unit. Hansen's BMW in Medford (amazingly GOOD shop!) advised me to have the Motoronic re-flashed. I've not been able to find out where to do that. Perhaps there's an easy fix? I can live without an odometer, but it would be nice to have the bike performing to spec. 'Don't know if there will be any response from BMW on this. 'Can't blame them for not wanting to research a 17 year old issue. I've got to hand it to the corporate office however, they covered $1.5K in recall work on the beast!

    Thanks for letting me bounce this off you!

    -l-

  6. #6
    Registered User lkraus's Avatar
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    As revs build, the timing for Hexhead lower coils changes so that they no longer contribute to cylinder firing. If you have a bad primary coil (or just a bad coil connection), the engine will run OK at lower revs, but loose power and stumble under heavy load and high revs.

    I experienced this after immediately after refueling at a rundown gas station far from home, which caused me to waste several weeks trying to correct a non-existent fuel problem. The engine would start, idle and run fine up to almost 4000 rpm, but would usually fall flat at higher revs and on acceleration. Eventually I found that a primary coil wire had not been fully seated during earlier maintenance work and the connection was intermittent.

    You might try taking a short ride after unplugging one of the primary plug wires. If the engine runs just as poorly, that coil (or connection) was probably the problem. If the problem is much worse, you unplugged a good coil, so try the test on the other side. If you have identical results, the primary coils are not the problem.

    An ohmmeter cannot tell you if a coil is good or bad.


    Edit - From the introductory press release for the Hexhead R1200GS, which uses the same engine:
    Featured in all BMW Boxers since 2003 (with the exception of the 850cc power units), dual ignition has been further modified and improved on the R1200GS. The auxiliary spark plug is now arranged at the outer edge of the cylinder, the ignition timing of both plugs being freely programmable as a function of load and engine speed in order to further optimise running smoothness, emission management, and fuel economy. Referred to as "phase shift", this adjustment process is maintained consistently all the way from part load to full load.

    In practice, this means different ignition timing points on both spark plugs in defined control map areas. When approaching full load, where dual ignition no longer provides any benefits, the phase shift effect is so large that the spark crosses over on the auxiliary plug in the expansion cycle (60 degrees at TDC). For all practical purposes this corresponds to single ignition on the central spark plug under full load.
    Larry
    2006 R1200RT

  7. #7
    Registered User landev's Avatar
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    Interesting info. So the lower coils effectively "disappear" at higher revs? That's some pretty amazing engineering, eh?

    Coil replacement is on the game plan should everything else fail. I was close to purchasing coils from RMStator until I ran the bike yesterday. Prior to checks and adjustments that I made, the bike ran so consistently bad that I figured it was either coils or a fuel pressure issue. After I balanced the TBs and took it for a ride yesterday, it seemed that all the issues were gone... for 28 miles. I climbed a substantial hill with some hard throttle ~ 13 miles into the ride and all was fine. It wasn't until the second hill climb that performance went south. That's what made me think more towards it being a fuel issue.

    I just remembered that, while warming the bike to operating temp (just ran it on the lift) there were probably 5 or 6 occasions that the bike did a hard stutter with a loud knock while idling (GS911 reported no temperature changes between the cylinders.) Prior to valve adjustment, plug change, and TB balancing, the bike did the hard stutter at idle a couple of times after getting home from the fuel pump recall service. That made me rethink the fuel supply possibly being the issue. I've not experienced that stumble at idle issue since completing adjustments.

    My current course of attack is to run a bottle of Techron as GTRider suggested and if I don't see improvement, I'll pull the pin on some coils. Does that seem like a reasonable tack?

    A full 4 coil replacement with RMStator coils is ~ $225. Reviews on these coils seem to all be positive and they have 2 year warranties. Anyone have any experience with these?

    Thanks for all the help!

    -l-

  8. #8
    Registered User landev's Avatar
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    I was sidetracked with ABS issues, so was unable to pursue this. Brakes are again up to snuff, so am tinkering with this again now that it's roadworthy.

    Fueled the bike this afternoon, put in the Techron, but have only ridden the 15 miles to town and back thus far. It occurred to me to test the throttle on the highway in lower gear. The ST is very tall with regards to gearing, so I was assuming that it just cut out at 65 mph at full throttle when I was riding in 5th and 6th.

    Hard throttle in 2nd gear showed the same issue, i.e. coughing and loss of power. What I noticed in the lower gears was that I could hold the throttle wide open... it would cough badly until the bike hit just below 5K rpm, then it cleared its throat, smoothed out and ran very strong and very fast. This was consistent behavior among 8 attempts. 'Seems like the issue is at 4K-4.8K rpm with a wide-open throttle. Once beyond 5K rpm, still at wide open, the bike takes wing and shows no hesitation. If this were a primary coil issue, shouldn't it cough consistently above 5K rpm?

    This is pretty much beyond me... sure is starting to feel like an electrical issue again though... funky Motoronic?

    Going to ride it a bit tomorrow and see if there is any change with the additive.

    Thanks for your help!

    -l-

  9. #9

    I have the same issues.

    I'm new to BMW and picked up a R1200-ST which has the exact same problem as yours. it runs perfect until you nail the throttle. It only has 15K total mileage but sat for years. The previous owner did have a new fuel pump put in .

    Did you ever find the final answer toy the problem? Thanks Rob

  10. #10
    Registered User landev's Avatar
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    Hi Rob,

    Nope... still working on the issue. I've changed out most everything that I could think of with regards to spark and fuel supply. I'm currently waiting for a new-to-me ECU from France... 'suspecting that the previous ECU programming by a local shop made the bike run bollox. Do you know if your bike's had someone tinker with the electronics?

    There's another thread going with regards to reprogramming the ECU and Motoronic units that might have more info that may be helpful to you.

    I'm curious if the symptoms you are experiencing are exactly the same. I found that the issue clears up above 4.8K rpm... the scooter then flies down the road like a screaming banshee. Are you experiencing the same "clearing of the throat" on your bike at those RPMs?

    It's damned curious... 'become a "thing" with me... i.e. I'm bound and determined to figure this out!

    Thanks for bringing your experience to light on this.

    -l-

  11. #11
    Most likely bad primary coils. They can have dead spots in the rpm range. So your 4-5k stumble is not uncommon, I have seen that dozens of times. The other possibility is the TPS. A bad TPS is a little harder to diagnose. If the bike has a complete sudden loos of power then TPS is suspect. If it feels like it is dropping a cylinder and running on 1/2 power then bad primary coil.

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