The background story: The front sprocket on my 2007 G650X Challenge was replaced by a Drive Systems USA sprocket at about 6K miles. At about 8K miles I was stopped dead in my tracks on the 1st day of a week long ride. The cause was due to stripped splines on the front drive shaft and sprocket. The sprocket bolt and spring washer were still in place and tightened to spec. From the photos below you can see the damage. You can also see a line of teeth that remain in tact on the Drive Systems USA sprocket. This line of teeth corresponds to a notch in the drive shaft which confirms that the sprocket was installed in the correct orientation. I've also included a capture of the letter that drive systems USA sent me today, excusing themselves of any responsibility because of the "unknowns" concerning my bike. Since I know that many people perform their own minor maintenance like I do, you might find it interesting that Drive Systems USA will not stand behind their product unless the sprocket installation is "performed by a professional motorcycle mechanic". It seems to me like a cop out when their products are targeted towards DIY owners. The letter also goes on to say that the failure was really BMWs fault, and that the BMW Drive-Shaft was flawed. I find this hard to believe since the splines on the BMW shaft held up for the most part, while the Drive Systems USA sprocket disintegrated. In the letter Drive Systems USA states that "Touratech, which specializes in BMW parts, has told us that, prior to hearing from you, they’ve never had a problem with this sprocket or any of Drive Systems parts that have been purchased in the past." This claim, at least in my limited research, is false as I have been in contact with 2 inmates that have had the exact same sprocket/spline failure (one on a XChallenge, one on an XR); one of which provided me with copies of emails between himself and Touratech (dated in 2009) about this very issue. When I picked the repaired bike from the dealer almost 2 months later, I also was given a letter stating the dealer's opinion of what had happened. In the dealer's letter they citied either incorrect spline tolerances, an incorrect sprocket having been installed (since they did not have Drive Systems USA part numbers to reference off the sprocket), or inferior metals used in the production of the sprocket. Total cost to me for repairs $1753.63. I'm pretty confident that I would have an open and shut case in small claims court with my quantity of evidence, but since Drive Systems USA is in California and I am in Washington, I would have to sue them in California... either that, or go after the local company that sold the sprocket. I wish to preserve the good relationship I have with my local company (which has been awesome throughought this affair), so as a result my actions end here. My takeaways from this experience are: 1) Sick to OEM, at least on the front sprocket. 2) Drive Systems USA's business practices are ultimately dishonest. ---- Timeline for those interested (~5 months): 8/12/2011 - Sprocket Failure 8/15/2011 - Motorcycle is dropped off at dealer for repairs - Initial Phone Call to Drive Systems USA - Email sent to Drive Systems USA with attached photos 8/16/2011 - No response from Brian Lewis - Sent follow-up email 8/22/2011 - Email response from Brian Lewis stating that damage was not sprocket failure - I respond via email to Brian's mail further describing failure and intention to have it repaired by a BMW Service Center - Brian responds that the cause was not the sprocket and that thousands have been sold without issue. - I respond asking questions about sprocket spline tolerances and ask for future compensation for repair costs yet unknown 8/23/2011 - Email from Brian claiming that installation failure was my fault, and that the sprocket should have been installed by an authorized service center. Therefore reimbursement for any repair costs will not be considered. 10/1/2011 - Bike repair is completed by dealer, and is picked up with letter from dealer stating sprocket is cause of failure. 10/5/2011 - Letter sent from my attorney to Drive Systems USA requesting compensation for $1753.63 10/12/2012 - Email from Brian Lewis acknowledging receipt of the attorney's letter and asking me a number of questions about the bike - most are irrelevant to the sprocket failure. - I respond via email to all of Brian's questions 10/20/2011 - Follow-up email to Brian as he has not responded to my earlier mail with the answers to his questions 10/21/2011 - Email from Brian stating that they would be mailing an official response 11/4/2011 - Official response received. In a nutshell: Drive Systems USA will not accept any responsibility before being able to examine the failed parts. Pictures and letters I have sent thus far are inadequate. 11/13/2011 - After deliberation I decide to send the parts to Brian for inspection. - Brian is Notified via Email that package has been sent 11/18/2011 - Follow-up email to Brian, confirming that he knows the parts are on the way. - Email from Brian acknowledging that he will be waiting for the parts to arrive and will let me know when they do. 11/30/2011 - Emailed Brian to see if parts had arrived, as I never received any notification that they did (other than UPS tracking information). 12/2/2011 - Email from Bryan saying that parts had been received and would be examined within the next week by Steve. - Email from me thanking Bryan for the update. 12/19/2011 - Email from me asking Brian if Steve had had an opportunity to examine the parts yet. 1/3/2012 - Email from Brian saying that Steve has the parts but has not had a chance to examine them yet. It will be another week. 1/13/2012 - Email from me asking if Steve has had a chance to look at the parts yet. 1/17/2012 - Email from Brian saying that the parts had been examined and would be shipped back along with an official letter. 1/24/2012 - Parts arrive. No letter or correspondence of any kind. - Email sent to Brian asking for letter. 1/25/2012 - Email from Brian with attached letter.