F800S Hesitation/stuttering on acceleration - BMW F800 Riders Forum & Registry



Remove this advertisement by REGISTERING.

Results 1 to 9 of 9
  1. #1
    Points: 7,153, Level: 59

    Location
    Devon, UK
    Joined
    Nov 2010
    Online
    4 Weeks Ago
    Posts
    38 / 0 / 1 / 0
    My 2006 F800S seems to have developed an aversion to full-bore acceleration.

    Runs fine on "normal" riding, but when given 75-100% throttle it hesitates and stutters for a second or two before clearing and then it accelerates fine and will go up to the redline. I think this is a relatively recent thing as I've only noticed it the last two weeks.

    Fuel regulator ECU thing was replaced a month or so ago, so suspected that at first, but they seem to be either working or not working (so no fuel and bike won't start) thing.

    Where to start looking? Air filter? Plugs and coils? Again, the fact that the bike work with gentler throttle applications and will rev out makes me think that these must be OK

  2. Remove Advertisements
    F800Riders.org
    Advertisements
     

  3. #2
    Points: 8,155, Level: 63

    Location
    Berkshire, UK
    Joined
    Jun 2013
    Online
    12 Hours Ago
    Posts
    620 / 0 / 2 / 32
    if you blip the throttle at idle, does it do the same?

    If so I would be checking the airbox is seated correctly and there are no air leaks. Check the Idle Control Valve Vacuum hoses too.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, 

  4. #3
    ccramerusc's Avatar
    Points: 7,507, Level: 60

    Real Name
    Cramer
    Location
    Milwaukee, WI
    Joined
    Jun 2013
    Online
    6 Hours Ago
    Posts
    561 / 0 / 0 / 6
    Motorcycle
    '08 F800ST
    It would be worth considering the throttle position sensor as the culprit. It went bad in my ST, but at the low end of the RPM range, so mine struggled to idle. Try to reset it to see if it temporarily fixes the symptoms.

    1. Turn on ignition but do not start the bike
    2. Turn the twist grip from zero to fully open and hold fully open for 5 seconds
    3. Wait 5 seconds and repeat step 2. another 4 times (do 5 times in total)
    4. Then turn off the ignition and wait at least 15 seconds before turning the ignition back on.
    5. Ride and try



    Sent from my SAMSUNG-SM-G891A using Tapatalk
    08' F800ST- side panniers & Shad SH45 top case, Russell Day Long seat, MRA Vario Windscreen, SW Motech crash bars, ZTechnik exhaust, PC-8 fuseblock, Stebel Nautilus horn, Throttlemeister throttle lock, SW Motech handlebar risers, LED fog lights, highway pegs 

  5. Likes308bever liked this post
  6. Remove Advertisements
    F800Riders.org
    Advertisements
     

  7. #4
    Points: 8,155, Level: 63

    Location
    Berkshire, UK
    Joined
    Jun 2013
    Online
    12 Hours Ago
    Posts
    620 / 0 / 2 / 32
    Quote Originally Posted by ccramerusc View Post
    It would be worth considering the throttle position sensor as the culprit. It went bad in my ST, but at the low end of the RPM range, so mine struggled to idle. Try to reset it to see if it temporarily fixes the symptoms.

    1. Turn on ignition but do not start the bike
    2. Turn the twist grip from zero to fully open and hold fully open for 5 seconds
    3. Wait 5 seconds and repeat step 2. another 4 times (do 5 times in total)
    4. Then turn off the ignition and wait at least 15 seconds before turning the ignition back on.
    5. Ride and try



    Sent from my SAMSUNG-SM-G891A using Tapatalk
    At idle the ICV does everything. TPS is only active with the throttle bodies, which the ICV by-passes.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, 

  8. #5
    ccramerusc's Avatar
    Points: 7,507, Level: 60

    Real Name
    Cramer
    Location
    Milwaukee, WI
    Joined
    Jun 2013
    Online
    6 Hours Ago
    Posts
    561 / 0 / 0 / 6
    Motorcycle
    '08 F800ST
    The ICV does everything only if the computer tells it to. The computer will only tell it to if it gets the correct voltage from the TPS indicating that the throttle is indeed closed. In my case, the potentiometer went bad at the lower end, so it wouldn't run or idle unless I gave it enough throttle to stay above the "threshold" of damaged resistor. So the computer was never told to activate the ICV. The only way I could start it was to hold the throttle slightly open while hitting the start button and then keep RPM above 2K. This symptom came and went. I could typically do a TPS reset and it would run normally for a while, then the problem would show up again a few minutes, a few hours or even a few days later. There obviously was a short in the resistor of the TPS. Other symptoms it showed was a jumpy and hesitant throttle while riding. My guess is that the voltage that the TPS was sending the computer would jump around which would cause the computer to abruptly change the fuel mapping. I changed the TPS and haven't had a problem since.

    Since fuel mapping is almost certainly causing the symptoms, he should look into any of the variables that impact the computer's decisions on fuel mapping. They would include pretty much every sensor and feedback system teh bike has including air box leak, vacuum hoses, the TPS, air intake temp, etc.

    A faulty TPS could result in the hesitant and stuttering mentioned by the OP, hence my suggestion to try and reset it. If it works, then that's probably the only problem and is pretty cheap and easy to fix. I replaced mine in my garage with a used one off a R1200GS.
    08' F800ST- side panniers & Shad SH45 top case, Russell Day Long seat, MRA Vario Windscreen, SW Motech crash bars, ZTechnik exhaust, PC-8 fuseblock, Stebel Nautilus horn, Throttlemeister throttle lock, SW Motech handlebar risers, LED fog lights, highway pegs 

  9. Likes308bever liked this post
  10. #6
    Points: 7,153, Level: 59

    Location
    Devon, UK
    Joined
    Nov 2010
    Online
    4 Weeks Ago
    Posts
    38 / 0 / 1 / 0
    Quote Originally Posted by ccramerusc View Post
    It would be worth considering the throttle position sensor as the culprit. It went bad in my ST, but at the low end of the RPM range, so mine struggled to idle. Try to reset it to see if it temporarily fixes the symptoms.

    1. Turn on ignition but do not start the bike
    2. Turn the twist grip from zero to fully open and hold fully open for 5 seconds
    3. Wait 5 seconds and repeat step 2. another 4 times (do 5 times in total)
    4. Then turn off the ignition and wait at least 15 seconds before turning the ignition back on.
    5. Ride and try



    Sent from my SAMSUNG-SM-G891A using Tapatalk

    Thanks for the tip. Tried it this morning, but unfortunately it hasn't cured the problem.

    On the ride in to work i tried a few experiments to see if i could nail it down any more.

    If you ride with around 0-60% throttle movement it is fine - revs up to the redline smoothly in all gears (well, up to fourth, i chickened out of redlining 5th and 6th on the morning run to work!)
    It bogs down/stutters with more extreme throttle openings - so when you go to make an overtake, for example. Seems to be around the 3000-4000rpm area when it does it. Once above 4500rpm it is fine and will rev normally.

    It idles fine, and at doesn't show any indication of hesitation at small throttle openings.

  11. #7
    ccramerusc's Avatar
    Points: 7,507, Level: 60

    Real Name
    Cramer
    Location
    Milwaukee, WI
    Joined
    Jun 2013
    Online
    6 Hours Ago
    Posts
    561 / 0 / 0 / 6
    Motorcycle
    '08 F800ST
    That sounds more like it's running too rich. Maybe oxygen sensor problem? It would be interesting to see if you are getting any smoke out the exhaust when you get heavy on the throttle. If that's the issue, it would smoke with abrupt throttle changes even with it parked on its side stand in neutral. Plus your gas mileage would be low.

    Of course the opposite might be true. Maybe a fuel injector or fuel pump issue, or even a bad spark plug or coil?

    It might be worth having the shop run some diagnostics. There are a lot of variables and sensors that can impact those symptoms.

    Sent from my SAMSUNG-SM-G891A using Tapatalk
    08' F800ST- side panniers & Shad SH45 top case, Russell Day Long seat, MRA Vario Windscreen, SW Motech crash bars, ZTechnik exhaust, PC-8 fuseblock, Stebel Nautilus horn, Throttlemeister throttle lock, SW Motech handlebar risers, LED fog lights, highway pegs 

  12. #8
    Points: 318, Level: 6

    Joined
    Sep 2019
    Online
    4 Weeks Ago
    Posts
    25 / 0 / 0 / 0
    Your clutch is starting to go, it's slipping and reengaging. check your clutch cable adjustment. contact me if you are interested in a hydraulic clutch kit to replace your cable operated one and make riding your bike even better than it already is...

    I Just put a DynoJet Power Commander 5 on my wife's F800S and it rode like a NEW bike. it was an incredibly gratifying experience, and the unit was a cinch to install and program.

    -David
    -Rocket Cycles

  13. #9
    Points: 8,155, Level: 63

    Location
    Berkshire, UK
    Joined
    Jun 2013
    Online
    12 Hours Ago
    Posts
    620 / 0 / 2 / 32
    Quote Originally Posted by Spark691 View Post
    Your clutch is starting to go, it's slipping and reengaging. check your clutch cable adjustment. contact me if you are interested in a hydraulic clutch kit to replace your cable operated one and make riding your bike even better than it already is...

    I Just put a DynoJet Power Commander 5 on my wife's F800S and it rode like a NEW bike. it was an incredibly gratifying experience, and the unit was a cinch to install and program.

    -David
    -Rocket Cycles
    if the clutch was going the revs would rise and the speed would not, this would very clear especially at higher revs.

    His problem is the engine stuttering at WOT. A slipping clutch would mean the engine would red line and the bike goes no where faster.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, 

  14. Likesbmwroadsterca liked this post

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •