2021 C400X vibration ( fixed )

MikeC

New member
Hi Guys,
I have a 2021 C 400X that I bought new and have only covered 180kms. At a steady 60 kph it has a terrible vibration coming from the engine area, just a vibration, no noise at all.. Also, If I decelerate from around 100/110 kph it also has the same horrible vibration.
There is no noise or vibrations when turning as reported elsewhere on this forum.

Can anyone help to shed some light on the cause of this, or what the fix entails.
 

MikeC

New member
After an afternoon of investigating the source, I found what was causing it and probably also what causes vibrations during cornering.
I`m amazed that BMW hasn't managed to spot this simple issue.
Anyway, it completly transformed the feel of the bike. Now it feels like the one I test drove before I purchased a new one.
 

crackanoon

New member
After an afternoon of investigating the source, I found what was causing it and probably also what causes vibrations during cornering.
I`m amazed that BMW hasn't managed to spot this simple issue.
Anyway, it completly transformed the feel of the bike. Now it feels like the one I test drove before I purchased a new one.
what did you discover causing the vibration
 

MikeC

New member
what did you discover causing the vibration
what did you discover causing the vibration
I found two causes for the engine vibration transfer.
1. the mounting bolt was way too tight, not allowing the cantilever part of the mounting to move .
2. the main cause of the vibration transfer is the slotted washer that under operation it touches ,ever so slightly, the outside of the mounting. this is enough for the vibration
to be transferred into the body of the scooter.
The fix:
1. Remove the nut and slotted washer on the right end side.
2. fit a copper washer with a 16mm inside diameter into the the bolt (photo)
3. fit the slotted washer back but this time with the slotted faces in the horizontal position ( see photo )
4. tighten the bolt again with just a good snug. Do not over tighten it.
In my scooter this simple mod totally transformed the smoothness of the bike.
 

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Donnus

Member
I found two causes for the engine vibration transfer.
1. the mounting bolt was way too tight, not allowing the cantilever part of the mounting to move .
2. the main cause of the vibration transfer is the slotted washer that under operation it touches ,ever so slightly, the outside of the mounting. this is enough for the vibration
to be transferred into the body of the scooter.
The fix:
1. Remove the nut and slotted washer on the right end side.
2. fit a copper washer with a 16mm inside diameter into the the bolt (photo)
3. fit the slotted washer back but this time with the slotted faces in the horizontal position ( see photo )
4. tighten the bolt again with just a good snug. Do not over tighten it.
In my scooter this simple mod totally transformed the smoothness of the bike.
i have the same vibrations in my 2021….
did you work on the side of the scooter the same side as the the exhaust ? Could you put a pic zoomed out so that i can see better ?
i want to do the same this week, thx
 

MikeC

New member
Exhaust side. On the other side is the bolt head that you must hold with a wrench in order to loosen the nut on the exhaust side.
 

hannesd

New member
thank you so much!
for me it was the overtorque of the nut that made it vibrate worse.
now just snug the nut and vibrations GONE completely ,super happy with this now.
 

wallyging

New member
The original slotted washer has been superseded by a smaller one.

I would NOT RECOMMEND a lower torque for the large mounting bolt connecting the rear engine/swingarm to the frame - BMW calls for 133 ft/lbs.
 
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