Tech Question For Expereinced BMW CVT Bike Owners

[mzflorida]

Hi everyone. I am placing this in this thread as I’d like to get input from a wider group of owners. The question is about a 23 C400GT. I have just shy of 2000 miles on it. I’ll describe the problem as best as I can.

When I ride the bike at speed and accelerate through ~41 to ~60 I can feel a cyclical vibration. However, it is not synchronous. The vibration starts out with a wide pattern them moves to a short pattern, then back to wide. To describe the type of vibration, it feels close to the engine braking a CVT provides while the accelerator is off but the clutch is still engaged. The intensity of the vibration neither increases nor decreases throughout its repeating pattern.

To kind of give you a visitation the pattern of the vibration starts out very wide like the receiving end of a funnel, and ends very close like the draining end of a funnel. So wide pattern to short, to wide to short, etc. 55555 4444 333 22 1, 55555 4444 333 22 1 would be the frequency, but the intensity does not change. It is detectable but not disruptive. Performance of the bike does not seem to be impacted but by human (not diagnostic) observation only.

It is not a tire issue. Did an ad hoc rotor run-out measurement and they seem remarkably true (plus would not be relative to an issue presenting a specific speed range), bearings seem to be perfect, all the usual suspects check out. It is under warranty so I can just take it in but was wondering if this was somehow a normal characteristic of BMW CVT systems; if not, I was wondering where I might direct the tech to start.

EDIT: The bike is stock except for an Admore light bar in the rear and Skene Photon Blasters up front. I'm putting the question on advrider.com too. First thought goes to springs.

Thanks! MIke

 

[Ceesie76]

Does not sound normal to me. Has the bike done this since new, or did this start more recently?
I would take it to the dealer and let a tech experience it for herself. If she says, totally normal, then I would ask to ride a demo bike, just to confirm it is indeed normal (likely not).
Good luck, my C650 is my third CVT scooter (been riding them for 14 years now) and none of the three have had a kind of vibration you describe.

 

[mzflorida]

Does not sound normal to me. Has the bike done this since new, or did this start more recently?
I would take it to the dealer and let a tech experience it for herself. If she says, totally normal, then I would ask to ride a demo bike, just to confirm it is indeed normal (likely not).
Good luck, my C650 is my third CVT scooter (been riding them for 14 years now) and none of the three have had a kind of vibration you describe.

Thank you. I sincerely appreciate the response. They are replacing the seat under warranty (had one seat at the shop but BMW shipped it without a light which is for some other market than the USA and they have no idea how it got to a US dealer). I'll just add this to that service. Thank you very much again.

I think it has developed in the last few hundred miles. I am thinking some sort of spring or forces that are exerting pressures on a spring causing it to behave this way. I did just notce that the idle rpm is at 1600 to 1700 instead of 1400 to 1500. Oddest thing in that the intensity of the vibration does not increase or decrease.

 

[wspollack]

Does not sound normal to me. Has the bike done this since new, or did this start more recently?
I would take it to the dealer and let a tech experience it for herself. If she says, totally normal, then I would ask to ride a demo bike, just to confirm it is indeed normal (likely not).
Good luck, my C650 is my third CVT scooter (been riding them for 14 years now) and none of the three have had a kind of vibration you describe.

As I recall, Mike had to order his C 400 GT. Like most dealers (as far as my experience has been), I don't believe that his had any of those scoots sitting around, demo or otherwise. So that part of your suggestion may be problematic.

 

[RollaCosta]

It may be worth to check (with a tensioner/extender) or replace the clutch flyout springs.
I seemed to have had a similar situation until i have replaced the clutch with a Dr.Pulley one.
That also helped continuity of torque.

 

[mzflorida]

It may be worth to check (with a tensioner/extender) or replace the clutch flyout springs.
I seemed to have had a similar situation until i have replaced the clutch with a Dr.Pulley one.
That also helped continuity of torque.

Thank you for the response! Unfortuantely, I don't have a tool to perform that test. I presume the dealer would though. There is no perceivable impact to performance though.

 

[mzflorida]

As I recall, Mike had to order his C 400 GT. Like most dealers (as far as my experience has been), I don't believe that his had any of those scoots sitting around, demo or otherwise. So that part of your suggestion may be problematic.

MIght get lucky. The last time I was in for the seat (without the light) they had a 23 in stock at Gulf Coast. Seems motorcycle sales are slowing a bit and prices are dropping.