Sudden onset engine buzz at 4k - BMW F800 Riders Forum & Registry



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  1. #1
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    BLUF: doing 50 or so and had the bike suddenly start buzzing like I didn't have a counterweight. Nothing in the oil. No mount issues I could find but fairing cross brace was loose. Buzz comes on quick at 4k rpm, didn't push it to see if it went away or got worse... Any ideas?

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    Looooooong version:
    Had a sudden onset engine buzz while driving on a straightaway at about 50... Pulled over, on the center stand, rolled both tires looking for bearing or brake issues. Pull the dipstick, shine a light in... no glitter or anything visible.

    Back on the road and nothing odd up to 4,000 RPM. No matter the gear, 4 to 4.2k starts the buzz... pretty reliably at 4K.

    Made my way home under 3.8k. back on the center stand, drain the oil, nothing, pull the filter, nothing but no spare so didn't cut it open.

    Side panels off... turn signal clip is completely impossible to pull off until you see the tab you have to lift and then it's insulting easy
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    One under-panel screw missing... but this bike is so well designed, the chin fairing held the screw for me until yesterday

    Side fairing brace that crosses over the back of the engine is loose enough to rattle, but both bolts have red loctite... some very focused torch heat... got them out, cleaned up and reinstalled with blue lock tight. Could the combined side panels and brace harmonically shake the bike?

    While I'm in here, pried up on the engine to see if anything was shifting or clunking, then vacuumed some random debris away. Didn't have the official BMW crevice tool or 2x4 so I improvised. Was sure to clear away that worrying oil sludge from under the water pump weep hole, then pretended I didn't see a thing, but set a calendar reminder so I can pretend it's nothing again in a month.
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    Picking up a filter today so I can cut up the old one but there was absolutely nothing on the drain plug magnet or my drain pan magnet... (VW beetle taught me to run drained oil over a magnet)

    Haven't run beyond a brief warm up post oil change, and certainly haven't been on the road.

    Don't think it was the fairing brace because there wasn't much paint scraping you would expect from something moving that strongly... (VW beetle for ref again having vibrated through a heat shield)

    Open to suggestions. Everything was tight other than the fairing cross brace. Will get her on the road again today to see if anything changed.

    Cheers and thanks for reading my novela
    Last edited by VinceNStuff; 06-27-21 at 01:18 PM. Reason: Pics added

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  3. #2
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    Do you feel the buzz through the handlebars/seat/frame?

    Being at a continuous RPM, and not speed related that would say to me it is potentially engine mounting/frame related.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  4. #3
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    Buzz is everywhere. Definitely in the bars and pegs but also in the seat. I didn't get much above 4K but it seems to follow rpm.

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  6. #4
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    Could an engine mount be loose?
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  7. #5
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    How many miles on the bike? Have the valves been checked/adjusted at the proper intervals?
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  8. #6
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    I just passed 40k miles 2 weeks ago, not sure on the last valve adjustment but the vibe came on so suddenly that I'd swear something let go somewhere.

    I checked all the motor mount bolts and nothing was loose...

    One light run around the valley and it seems to have gone away but I'll get it out for a longer ride soon to make sure

  9. #7
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    Have you swapped any parts?
    In particular a new exhaust?

    Do you have any of the oil you drained out?
    You could send it off for analysis if so ...
    I used these guys and they were awesome: http://www.blackstone-labs.com/
    (If for no other reason than piece of mind
    Blue 2009 F650GS - H-B crash bars, TT luggage rack, Pelican top case, BMW Vario Panniers & bash plate, 20mm handlebar risers, LED voltmeter, Sargent seat, MudSling, a few other trinkets ... I may be just about at the end of the farkle train  

  10. #8
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    Jim reminded me that I once installed a plastic top box on my 1997 Funduro which resulted in a noticeable increase in vibration at higher engine speeds.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  11. #9
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    Thanks all for the thoughts. Buzz is still there, right on que at 4K rpm. I'll have to pull the plastics again and re-torque the engine mount bolts (though I don't have a socket for the huge torx locknuts). I may also have the miss' rev it up on the center stand and probe around with a stethoscope...

    I've used Blackstone Labs before, when I found out the 100K mile service for my prius didn't include the ATF flush I asked for... fluid was surprisingly good after 200K miles. Unfortunately, the oil is already in my recycling jug with oil from 2 other bikes and the prius...

  12. #10
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    You might have something totally unrelated to the bike itself causing this.

    My GT had a buzz from the beginning from about 3800 to 4000 rpms. I didn't even have to look at the tach to see what it read, it was so reliable. But at 30,000 miles the engine smoothed out and the buzz went away. So I was surprised to see you got your vibration at 40K.

    I had a really bad buzz or vibration a couple weeks ago that had me concerned that something had come loose on the fairing. Checked everything and had no issues. I finally tracked it down to the magnetic holder for my radar detector. The magnets were loose if the detector wasn't in place and vibrated. With a helmet on, it was hard to pinpoint where the noise was coming from.

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  13. #11
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    Read through the other 4k rpm vibe posts on the site... Only fix I haven't tried is to loosen and re torque the engine mount bolts. Just did and will check in the am.

    I've had a few super smooth inline 4's, and still have an sr400 single that buzzes like crazy, but this is different. It came on quick, during a very mild stretch of road where I stay in 3rd to avoid breaking the speed limit on base. Was strong enough to warrant pulling over... Very different from my first 3.6k miles with the bike.

  14. #12
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    Quote Originally Posted by VinceNStuff View Post
    Read through the other 4k rpm vibe posts on the site... Only fix I haven't tried is to loosen and re torque the engine mount bolts. Just did and will check in the am.

    I've had a few super smooth inline 4's, and still have an sr400 single that buzzes like crazy, but this is different. It came on quick, during a very mild stretch of road where I stay in 3rd to avoid breaking the speed limit on base. Was strong enough to warrant pulling over... Very different from my first 3.6k miles with the bike.

    I used to own a 1978 Yamaha SR500 that was the smoothest single that I have ever ridden. I wonder why the smaller SR400 is not like that? Kind of makes you wonder why some motorcycles vibrate much more than others of the same model.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  15. #13
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    Quote Originally Posted by Richard230 View Post
    I used to own a 1978 Yamaha SR500 that was the smoothest single that I have ever ridden. I wonder why the smaller SR400 is not like that? Kind of makes you wonder why some motorcycles vibrate much more than others of the same model.
    I will say the little 400 is awesomely civilized around town, but I do lots of freeway riding and any time spent near the 7k redline is buzzy. +1 tooth up front helped quite a bit when holding 70 on the way to work, but I try to keep it on the back roads.

  16. #14
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    The ride post re-torque of the top engine mount bolts showed no difference. Harmonic vibration comes on at 4K and steadily gets worse above that.

    Tried with or without top and side cases. Pulled and reattached oem exhaust per another 4K vibe thread here. Tightened belt slightly since the prev owner had it a little loose. Have had all plastics off and checked torque on every visible fastener (none missing that I could find).

    Same vibration with and without load (full throttle or chopped while in gear so not likely a spark/timing issue). Same vibe on the road, side stand or center stand.

    Either the engine is resonating, or something substantial is resonating with it.

    I think next step is to drop the oil pan and counterbalance cover to see if there is any play in the mechanism... really doubt it since I would probably feel vibes at lower rpm's, like the 2k harmonic. shopping for gaskets...

  17. #15
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    Is it possible that something came loose in the exhaust system? If the catalytic converter or muffler baffles have come loose it could cause a harmonic vibration like this.

    I have not heard of it happening on the F800 before - but it happens occasionally in the mufflers on the Savage forum.

  18. #16
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    Quote Originally Posted by Thumpin View Post
    Is it possible that something came loose in the exhaust system? If the catalytic converter or muffler baffles have come loose it could cause a harmonic vibration like this.

    I have not heard of it happening on the F800 before - but it happens occasionally in the mufflers on the Savage forum.
    That also happens frequently with Royal Enfield singles that have the cat welded into the inside of their very long stock mufflers. But I agree that I have never heard of that happening with original BMW mufflers. The F800 models have the cat located in a very sturdy box under the engine, instead of it hiding in the muffler. While the baffles in the muffler might have come loose, I doubt there are any problems with the cat box. And original BMW mufflers are nothing if not heavy and well built. But that might not be the same with an after-market muffler.

    If you ever find out what the problem is and how to fix it, that will be a valuable piece of information for members on this forum.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  19. #17
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    How does it feel at 4.5K....at 5K rpm? If the buzz is still there, could be a fuel flow/pressure problem. Replace fuel filter/pump. Could a diagnostic tool (GS-911) help?

    BTW: At 4K rpm my GT runs smooth as glass
    Sundog 

  20. #18
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    Thanks all for the thoughts. OEM muffler and cat, mounts seem secure with minimal flex in the bushings. Will probably pull them off just to shake them around and verify the mounts.

    Wasn't thinking it could be a fuel or air issue but it's smart and easy to rule them out so installed a new air filter and fresh gas with a shot of seafoam.

    New iridium plugs about 6k ago (per last owner), but I've ordered a pair just to rule it out.

  21. #19
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    Quick thought, this started on yet another lovely 110 degree day on Edwards AFB... other than trying to roast my left leg, the bike never seems to mind the heat. Temperature has never risen above the lower tick mark (nor dropped below it on the brisk 35 degree mornings back in Feb).

    Just because I don't see a connection doesn't mean there isn't one, but the other 4k vibe threads around here don't mention temp extremes... Just thinking out loud

  22. #20
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    Quote Originally Posted by VinceNStuff View Post
    Quick thought, this started on yet another lovely 110 degree day on Edwards AFB... other than trying to roast my left leg, the bike never seems to mind the heat. Temperature has never risen above the lower tick mark (nor dropped below it on the brisk 35 degree mornings back in Feb).

    Just because I don't see a connection doesn't mean there isn't one, but the other 4k vibe threads around here don't mention temp extremes... Just thinking out loud
    It has been my experience over the years that all of my motorcycles vibrate a lot more when the air temperature is hot and dry than when it is cold and damp. Inline fours seem to be the worst vibrators when running in hot weather.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  23. #21
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    Quote Originally Posted by Richard230 View Post
    It has been my experience over the years that all of my motorcycles vibrate a lot more when the air temperature is hot and dry than when it is cold and damp. Inline fours seem to be the worst vibrators when running in hot weather.
    I've noticed the same, though mostly on my air/oil cooled bikes. I used to blame my summer gloves.

    This vibe comes on quick though, like someone switched on a jigsaw zip tied to the frame somewhere... It's that sudden and strong.

    Pretty clear something is harmonically resonating...

  24. #22
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    Quick thread resurrection since I finally managed to throw some resources at it. After hearing from two local shops that folks have just been riding with this vibe, I put another 2K mostly highway miles on the bike before taking this sample. Below is the oil analysis... basically nothing to see here.

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    Almost done rebuilding my Concours 1000 so this one will get a teardown soon. New job is keeping me busy but I'll let you folks know what I find... any year now.

    Cheers

  25. #23
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    No ideas how this "buzz" sounds, my closest assumption would be the timing chain (TC) and/or the TC guide.
    2017 F700GS - I wish she had a drive shaft. 

  26. #24
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    Seems unlikely that “people have been riding with this vibe” locally when internationally nobody has heard of it….
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  27. #25
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    100% agree with this vibration clearly not being normal. When I first searched through the forum, others were told "they all do that", but it started so suddenly for me, on a straight away at constant throttle...

    Another thread mentioned riding with it for a long time so I went ahead and pressed since this is my third bike. Interesting to see the oil report come back pretty clean.

    I almost got the concours back together, and a fresh plastigauge kit on hand. Will tear into it soon

  28. #26
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    Quote Originally Posted by guenner View Post
    No ideas how this "buzz" sounds, my closest assumption would be the timing chain (TC) and/or the TC guide.
    Early on, I went through all the externally accessible things.. timing chain tensioner was one of my first guesses as well but it's in good shape

  29. #27
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    I still believe you should investigate the exhaust system. My car got a buzz when a connecting bolt for a heat shield rusted away. Harley Dyna mufflers when mounted on a Suzuki Savage sound great - several riders have experienced a buzz after many miles when the inner core comes loose.

    At a minimum I would take off the muffler and shine a flashlight in both ends and make sure it all looks firmly attached - and see if you can see the catalyst in the header pipe and confirm it is not loose.

    Does the bike buzz at 4,000 rpm while you are stationary? Does the buzz happen in neutral with the engine cranked up to 4,000?
    Last edited by Thumpin; 2 Weeks Ago at 12:18 PM.

  30. #28
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    Quote Originally Posted by Thumpin View Post
    I still believe you should investigate the exhaust system...

    Does the bike buzz at 4,000 rpm while you are stationary? Does the buzz happen in neutral with the engine cranked up to 4,000?
    I haven't pulled the exhaust yet but the mounts are solid and there are no contact or rubbing spots.

    The vibe starts around 4k, +/- a hundred if I sneak up on it but very reliably at 4k. In gear or neutral, on the highway or on the center stand.

    Will definitely break down the exhaust and check everything when I get the C10 out of the way.

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