VINTAGE TECH: ATC CHAIN TENSIONERS
Chain drive tensioners served several purposes and became a very popular mod for ATC and sport quad riders in the 1980s, especially at the track. The device typically consisted of one or two urethane wheels, much like skateboard wheels with bearings, scissor brackets and a spring between the rollers. The spring squeezed the rollers and chain together, which eliminated the slack without making the chain so tight that it could possibly break.
Anyone that has ever installed a longer than stock swingarm on an ATC knows the value of a chain tensioner. Increasing swingarm length creates more chain slack and the possibility of derailing the chain from the rear sprocket. With a chain tensioner installed, there is no chain slack as the added tension won’t allow the chain links to slide off of the sprocket teeth.
Chain tensioners were also considered a performance upgrade. With the slop out of the chain, throttle response improved, especially when exiting a corner with the suspension compressed. This was especially important for smaller displacement classes, especially 200cc four-strokes, where mechanics did their best to squeeze every ounce of performance out of the smaller engines. A chain slider might only add a split second or two to a lap time, but that was usually the only difference between winning – or settling for second place.