WASHINGTON, D.C. - BMW of North America is recalling certain 2012-2014 model year scooters because the camshaft chain tensioner may not function properly, a condition that could stall the engine.
Involved are 2012-14 C 600 Sport Maxi-Scooters and C 650 GT Maxi-Scooters manufactured from Aug. 2, 2012, through Feb. 18 of this year. About 1,360 units are affected.
"As a result of an improperly produced camshaft chain tensioner, a clearly audible noise from the chain drive can occur because of an improperly adjusted loose chain," BMW told NHTSA. "If the noise is not noticed by the rider, an engine breakdown could result while riding the motorcycle. If this were to happen, the motorcycle will lose power and the engine may stall when decelerating, which could increase the risk of a crash. The engine cannot be started after stalling."
BMW told NHTSA it has been working on the noise and stalling issues since February 2013. In May 2013, excessive noise and a stalling condition appeared on an endurance test bike after about 15,500 miles; however, it was possible to restart that bike, BMW said, and the defective camshaft chain tensioner was returned to the part manufacturer, Kwang Yang Motor Co. Ltd. in Taiwan, for analysis. The Taiwan manufacturer in August 2013 identified the defect as a stamping burr which resulted in excessive wear on the camshaft chain tensioner.
"In August 2013, improved stamping tools and processes were implemented at the engine supplier to enhance the surface finish quality of the camshaft chain tensioner," BMW noted. "In December 2013, engines with the improved camshaft chain tensioner were first introduced to motorcycle production."
In November 2013, BMW said it received a field report from Korea indicating a unit that experienced engine stalling without an ability to restart. "The associated parts were not returned for analysis," the OEM added. This was followed in January 2014 by a field report from the Netherlands indicating an inability to restart the engine after shutting it off, and another report from Korea indicating that a unit was stalling while idling without an ability to restart. BMW received the camshaft chain tensioners from the last two reports for analysis and confirmed that they exhibited the same wear condition as found on the endurance test motorcycle. At that time, 42 warranty claims had been reported for this condition, mainly due to the excessive engine noise issue.
The recall is expected to begin in July. BMW told NHTSA it is notifying owners. Dealers are asked to replace the camshaft chain tensioner free of charge.
Posted by Mary Slepicka