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Thread: BMW F650st Engine Vibrations

  1. #1

    BMW F650st Engine Vibrations

    Hey, this is my first time posting on MOA so correct me if I'm posting in the wrong place. I have a 1997 BMW f650st. They are very similar to the funduro motorcycles. It's my first bike, and I bought a repair manual and have done every bit of maintenance possible, Tightened every bolt to specifications, and repaired everything on it that seemed off. The bike looks like it's in perfect condition, but there is still a major issue that has been there since buying it. The vibrations are horrible, to the point were I can barely go on a 15 minute ride. This is very disappointing considering I've added and bought everything needed to go on long distance trips. The vibrations are directly related to engine rpm. The more rpms, the more vibrations. whether it's in neutral or any gear. They start after 3500 rpms and get worse as it rises. The only thing I see it being is something with the counterbalance is messed up in the engine, but before I take apart the entire bike I figured I'd ask what you all think. What do you think might be the issue. 20190608_000349.jpg I attempted to attach a few photos, but don't know if I actually did.

  2. #2
    Liaison 20774's Avatar
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    Welcome to the forum! I'm guessing that you're not the first owner of the bike. Has it vibrated like this from the beginning? What about your test ride before buying? Does the previous owner have anything to add along with any major maintenance that was done?
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
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  3. #3
    Quote Originally Posted by 20774 View Post
    Welcome to the forum! I'm guessing that you're not the first owner of the bike. Has it vibrated like this from the beginning? What about your test ride before buying? Does the previous owner have anything to add along with any major maintenance that was done?
    Hey, thanks, I'm glad I found the forum. No, I've only owned the bike for the last 6 months. It has vibrated since I bought it, and sadly there was no test ride because I learned to ride on this bike and didn't know how to when I bought it. I haven't been able to get in touch with the previous owner probably because he knew about the vibrations when he sold it to me. It makes it a little harder to figure out the issue.

  4. #4
    We have the same bike... I put a 19” front wheel on mine because it’s easier to find tires in that size.

    I wish I could be of more help to you, but I don’t know what would cause the vibrations.

    And as much as I hate to steer you away from our site, the best source of expertise for this bike is F650.com

    Here is a search string on “vibration” ...

    http://f650.com/forum/search.php?searchid=1046587

    (Check the first post in the search... did you tighten the motor mount bolt that is up under the tank?)

    And... one thing (entirely unrelated) that I can tell you, if your Voltage Regulator is still located under the seat, you need to relocate it to a position on the right side, in front of the air box intake. It overheats and fails due to a lack of cooling air and then overcharges your battery... cooking it until it’s dead. Whatever you do, don’t go on a long trip without doing this modification. There is mucho info on this at F650.com

    Last, and this is just my opinion, you need to pack that bike lighter... it appears that it’s overloaded.

    Ian

    This is what happens when you put too much crap on your bike...



    Go soothingly through the grease mud, as there lurks the skid demon.
    __________________________________________________ __________________________________
    '67 Trail 90 || '86 R80 G/SPD+ || '97 F650ST || '00 1150 GS || '07 Xchallenge || '13 CB500X || '14 Grom

  5. #5
    Quote Originally Posted by Visian View Post
    We have the same bike... I put a 19” front wheel on mine because it’s easier to find tires in that size.

    I wish I could be of more help to you, but I don’t know what would cause the vibrations.

    And as much as I hate to steer you away from our site, the best source of expertise for this bike is F650.com

    Here is a search string on “vibration” ...

    http://f650.com/forum/search.php?searchid=1046587

    And... one thing (entirely unrelated) that I can tell you, if your Voltage Regulator is still located under the seat, you need to relocate it to a position on the right side, in front of the air box intake. It overheats and fails due to a lack of cooling air and then overcharges your battery... cooking it until it’s dead. Whatever you do, don’t go on a long trip without doing this modification. There is mucho info on this at F650.com

    Last, and this is just my opinion, you need to pack that bike lighter... it appears that it’s overloaded.

    Ian
    Thanks! I'll check out the other site. I'll get to changing that voltage regulator soon because it is under the seat and that makes a lot of sense. Haha, I completely agree with loading it lighter. This was actually from a short trip to see how it would do with a load like that, and I got rid of a ton of stuff on it that was unnecessary after the trip. does yours vibrate much?

  6. #6
    Quote Originally Posted by calebcrubaugh View Post
    does yours vibrate much?
    Mine is as smooth as glass, only gets “chuggy” when you let the revs drop too low in too high a gear. The engine is very happy above 3500rpm.

    Definitely do that VR mod... it is this bike’s Achilles heel.

    I just love this bike... it’s probably the first motorcycle I’ve ever named: Punkin’


  7. #7
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    What is the mileage? What does it say on the skid plate? NO something!
    Is your vibes in the seat, footpegs or handlebars?

  8. #8

    One other important tip...

    There are O-rings in the carburetors that get eaten up by Ethanol. Every time you’re heading for the barn, turn off the fuel tap about ˝ mile away from home so that your float bowls run dry. Once you get the hang of it, you’ll know just the right distance to turn off the tap.

    It is a MAJOR pita to R&R those carburetors.

  9. #9
    Quote Originally Posted by Visian View Post
    Mine is as smooth as glass, only gets “chuggy” when you let the revs drop too low in too high a gear. The engine is very happy above 3500rpm.

    Definitely do that VR mod... it is this bike’s Achilles heel.

    I just love this bike... it’s probably the first motorcycle I’ve ever named: Punkin’

    Hopefully mine will be that smooth soon. Haha, thats a good name for it.

  10. #10
    Quote Originally Posted by EUGENE View Post
    What is the mileage? What does it say on the skid plate? NO something!
    Is your vibes in the seat, footpegs or handlebars?

    The mileage is 36,000. Haha, the skid plate says No Semi Trucks. It was a damage road sign that was given to me. I modified it to become a cheep skid plate and it works perfectly. I left it like that instead of painting it to give it some character. The vibrations are all throughout the bikes frame so the footpegs, handlebars, and seat. The seat is the worst even with an air seat cover. The vibrations are the same or worse even with everything I've added to the bike taken off.

  11. #11
    Quote Originally Posted by Visian View Post
    There are O-rings in the carburetors that get eaten up by Ethanol. Every time you’re heading for the barn, turn off the fuel tap about ˝ mile away from home so that your float bowls run dry. Once you get the hang of it, you’ll know just the right distance to turn off the tap.

    It is a MAJOR pita to R&R those carburetors.
    Thanks for the advice! That is very true. I had to rebuild the carburetor when I bought the bike. It took me three times taking it apart before I was able to get it working perfectly. Hopefully I wont have to do that again for a very long time.

  12. #12
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    I also suggest f650.com. Make sure you get spark from both plug caps to ground. I had one of mine fail and the bike needs both to run smoothly. Other issues are broken carb vacuum piston membranes or issues with worn needles. Common is to remove the cannister on this bike and do a needle adjustment to get it to run a bit richer. My F650 gets 45 mpg but runs smoothly and strongly. Good luck.
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  13. #13
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    Harmonic Stick

    You could use what I call a harmonic stick to isolate the trouble. Find a 2 foot to 3 foot dowel. Put it against various parts of the engine and frame, place your ear to the end and see where it is loudest. Or if you want to spend a couple bucks and get something more precise, get one of these:

    https://www.harborfreight.com/mechan...iABEgJChPD_BwE

    Or one from these guys:

    https://www.homedepot.com/p/Lisle-Me...E&gclsrc=aw.ds

    If it only makes the sound while riding - you need a really, really good friend to ride on the back and try to find the source


    Wayne Koppa
    Grayling, MI
    #71,449

  14. #14
    Quote Originally Posted by chrisinsc View Post
    I also suggest f650.com. Make sure you get spark from both plug caps to ground. I had one of mine fail and the bike needs both to run smoothly. Other issues are broken carb vacuum piston membranes or issues with worn needles. Common is to remove the cannister on this bike and do a needle adjustment to get it to run a bit richer. My F650 gets 45 mpg but runs smoothly and strongly. Good luck.
    Thanks for the advice. I'll check all that out. Wouldn't it be really obvious if one of the spark plugs wasn't getting spark? would the bike still run ok enough to ride?

  15. #15
    Quote Originally Posted by wkoppa View Post
    You could use what I call a harmonic stick to isolate the trouble. Find a 2 foot to 3 foot dowel. Put it against various parts of the engine and frame, place your ear to the end and see where it is loudest. Or if you want to spend a couple bucks and get something more precise, get one of these:

    https://www.harborfreight.com/mechan...iABEgJChPD_BwE

    Or one from these guys:

    https://www.homedepot.com/p/Lisle-Me...E&gclsrc=aw.ds

    If it only makes the sound while riding - you need a really, really good friend to ride on the back and try to find the source


    Wayne Koppa
    Grayling, MI
    #71,449
    That's interesting. I've never heard of doing this and i'll definitely try it. Thanks. Luckly it's about the same just reving the engine up at idle as it is when riding. haha

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