Ceesie76
Active member
In a few other threads I reported that my 2016 C650 Sport with 13,500 miles on the clock last week developed a driveline vibration at higher speeds, upward of 75 MPH (120 KMH) that gets progressively worse the faster I go. It did not use to have this, or at least not nearly as noticeable. I concluded it would be better to create a new thread to document my attempts at finding and eliminating the root cause, for future use.
So far, I have come up with 4 likely causes:
So far, I have come up with 4 likely causes:
- Dirt in the CVT part
- Malfunctioning torsion vibration damper. As the name suggests, I imagine it does an important job in managing engine/driveline vibrations, so I bought a used one off Ebay: https://www.ebay.com/itm/254857202406 Original ones are available from BMW but at close to $700. I imagine they don't break easily, but my fear is that one of the internal parts (a heavy-duty spring, I imagine, as with car manual clutches, of which there seem to be 3 inside) has broken in two. Doesn't happen often, but in my years I have had broken valve springs and car suspension springs, so it can happen. Unfortunately, this thing turns out to be deeply inside the cranckase, driven by the crankshaft through a heavy-duty chain, so replacing it would be a major-major undertaking necessitating (I think) splitting the crankcase. What's more, I have not been able to find any reference to it in the service manual, and it may not even be installed in my engine as even that information seems conflicting depending on the source you look at. So, fingers crossed it's not that!
- too much play in my final drive chain. I ordered the 3 oversize chain guides/rails that we're supposed to install in 15,000 mile intervals give or take, depending on the degree of stretch of the chain. I measured (thanks again Delray!) the play by removing the oval black 'BMW' plastic plate and best I could tell the play is just about the maximum allowed (perhaps a bit more, or a bit less - hard to get a precise measurement) so I am going with this possible cause as the most likely one. Parts (second stage rail, fresh oil, gasket etc etc on the way). I did notice the inside of the case looks quite dirty. I have owned this bike since early 2018 when it had less than 2K miles (I paid $6,500 and still think that was a real bargain!) and have ridden it almost exclusively in Los Angeles as my commuter for the 7 mile trip each way each day. So, tons of brisk accelerating/stopping, lane splitting, short rides. I also like to go faaast so I think this bike has had a hard life so far which may well mean that the chain is indeed stretched to the point where it can cause this vibration at higher speeds. We'll soon find out.
- Drivebelt is worn out. Given the information in item 3, and the fact that BMW likes to see us replace the belt at 12,000 miles, which I have exceeded, I can't rule out the possibility that the belt is worn. In fact, recently, I was noticing that after coming to a stop, I smelt what seemed to be 'burnt rubber' .... First I thought I was imaginging it, then I thought it was from another source (road works e.g.) but since it happened a couple of different times, I started to think it had to be the bike. Not sure what it could be, other than the drivebelt? Nothing else made of rubber or similar that could smell the same, as far as I am aware. Pretty sure it wasn't the brake pads or the tires. I haven't noticed the smell recently, but that may not mean anything, beyond that it is possible the belt is worn/frayed/whatever and I need to change it. Since I recently moved from Los Angeles to closer to San Diego, my commute increased from 7 miles each way to ... 120 miles each way. Fortunately only once a week and I don't mind, but because I now pile on more miles, I decided to order 2 belts from CarpiMoto (the Mitsuboshi brand) just now. Total cost came to $180 including fast shipping. I also ordered the Easyboost CVT tool set from France, that came to another $128 delivered - I was going to need that set anyhow sooner rather than later. Still need to order the grease etc for the CVT clean/re-install. I will also order new CVT rollers and sliders as well, as that's due now according to the service manual.