Hi guys. First post and it's about .. . yup... the early model tensioner. First off my background. 5-time ASE Master Certified Mechanic, 35 years in the business, 10 years fixing Avionics in the Marines, a ton of certs and training through the years, and experience with way too many 'warranty' claims. So, that little noise in my scooters engine, that I'd traced to the Right side and thought it was the Variator weights because it went away after warm-up...yeah, it reached out and bit me about 10 days ago. Fortunately when it got REALLY loud, from the chain slapping around, I was 500 yards from my driveway, so I just coasted in at idle and waited to see what would happen. It was still running on both cylinders, then stumbled and lost power. I did NOT try to re-crank, though. When engines make bad noises then die, it's a really bad idea to try to restart after stall. So after I got it settled in the carport, I came on line and found THIS wonderful Forum (VERY much appreciate what you've been doing here) It took a few days to get over the depression of my scooter engine trying to eat itself, then I got to tearing things apart. I swear BMW intentionally, makes it difficult to work on this bike. But, I got the side cover off and the upper chain guide and chain are just slack. I can flop them up and down about 3/4" with ease. Yup, not good at all. I pull out the mechanical tensioner and disassemble, and the spring is broken. Okay, that sux so I took a picture. The bike has 11,000 miles and I was going to do the 12K service in a few months anyway, so I went ahead and started it now. Pulled the radiator and then got the plugs out and snaked my bore scope into each cylinder. Yup, small 'eyebrow' marks on the intake side of each piston. Sigh...Still, I re-timed the cams and manually locked the cam chain guide in place so I could spin it over to check compression, but all that did was prove that ANY sort of contact between pistons and valves is a BAD THING. Zero compression. Off came the head, and all 4 intakes need to be replaced. Pretty typical I'm guessing.
So...NOW I go to my local BMW/Ducati/MV Agusta dealer, carrying my bad tensioner and with all the Recall information on these tensioners. And then things REALLY start to go down hill.
First off, no one seems to be able to find the Recall. My Scooter was built in January-2014. The range of dates for the recall is August 12, 2022 to February 18, 2014. Mine was built in January 2014. All the engine parts were cast in December or January, the date on the Tensioner is January 25, 2014 (so it's almost a month inside the deadline) so the engine was put together in January, 2014. You'd think this is simple, right? But NO, not with BMW. First, they can't match my bike to the Recall for some reason, even though the recall stipulates that date range. Secondly, they try the 'but it was already replaced' because of the date of the tensioner (isn't that supposed to be an upgrade to a Hydraulic piece??) And since they are so befuddled by their lack of ability to research this they give me the number to BMW NA. BMW NA turns out to be just as befuddled and inept, so I call NHTSA, where I finally get ahold of someone who can think and breath at the same time, with their mouth closed even. An hour on the phone with this nice young man, and we go through all the things associated with this little issue, and I get ALL the information, as well as going through the process of initiating a complaint.
Then I start reading all the PDF's associated with the recall, especially the last one where BMW finally tells us WHY these things fail. Something about a 'burr' on a stamped part, which I find to be ludicrous. It's just so ambivalent and imprecise. What burr, on which part of the assembly? As you can see from the attached pic, the spring failed at the top, where it engages the winder feed, directly in line with the engagement slot. What in the world could make it fail right there? I did a close up examination of the surfaces of the stamped shaft, and right next to the groove's end is a small high spot, probably less than a millimeter but you can feel it when rubbing it. The other side does not have it. I lined things up and the break in the spring corresponds to that point exactly. People will say.. but it's just a little high spot...yeah, one that will touch the spring after tension is put on it by twisting it tighter against the internal barrel of the tensioner. Which means that after it's all assembled and put into the engine, under tension, the spring now rides on that small high spot, concentrating all the stress, vibrations, and harmonics on that one spot, rather than spreading it across the entirety of the spring and barrel. Over time, that work hardens the spring, the constant micro-hammering of vibration changing the metallurgy of that one spot and weakening it, until it finally fails.
So, now I have a pretty good idea what the cause of the failure is. I need more information from the community if I can get it so I can push this forward with the NHTSA. But a few questions as well. Aren't all C650's supposed to be upgraded to Hydraulic tensioners? It seems so according to the Recall. Secondly, if the 2nd generation Mechanical tensioners are failing almost as badly as the 1st design, doesn't that make BMW still liable, since their 'fix' obviously is NOT.
If anyone took the time to disassemble their failed tensioner and make pics of the internals I'd appreciate them forwarding or posting them. Finding a consistent failure point would be a big help. With enough evidence maybe we can all get refunds or future PROPER repairs for this issue from BMW. I'm certainly going to be pushing it. $450 worth of valves plus a head gasket and about 15-20 hours of time wrestling with the BMW cursed design of this scooter kind of requires me to get very much in some corporate drones face and rectify their problems.
As for my own bike? I'm probably going to get the hydraulic unit, but not from my local dealer (They have a tendency to lie to me), then have a local Hydraulic line shop make a line for it. I'll need the 1-way valve as well, but I should be able to get out of this for less than $300 to replace the mechanical tensioner. I'm pretty sure the Dealer is just going to dig in it's heels and it will turn into a head butting match. A set of used valves is coming from MSP, and I have a source for the head gasket.
If you've made it this far.. thanks for reading. Any inputs to get more information for that NHTSA complaint would be appreciated.
