Some maintenance tasks in modern motorcycling are so spaced out mileage wise that our knowledge of their steps can go rusty. In this case, it's the chain alignment on my daily rider's double-sided swing arm. Because drive chain adjustment is rarely necessary, the effects of turning one bolt versus another can be easily forgotten, so I've elected to document the process.
Backing out the alignment bolt on the right side of the swing arm moves the teeth of the rear sprocket to the right within the chain links.
For those new to wrenching, motorcycle chains stretch slowly over time and must be adjusted accordingly. The rear axle should then be tuned so that the sprocket's teeth are aligned center within each chain link. Where some riders may blindly trust alignment markings or a third party tool, others (myself included) will align the chain by sight. This technique is far more efficient and effective once we learn to equalize the alignment bolts, insuring the rear wheel's horizontal axis is properly positioned.
On my Bandit 1200, I "experimentally" trusted the alignment markings along its swing arm. This is a proven mistake. The outcome is a wheel that's off center, with a chain that's too tight to boot. Below are images of the very same nuts, bolts and markings after correcting the alignment. Comparing the left and right notch positions, the difference is obvious.
Additionally and as mentioned above, there are tools on the market for motorcycle chain alignment but they tend to be more trouble than they're worth. Sure, they're useful while the adjustment is being made but once it comes time to torque things back to spec, accuracy becomes questionable. Enter the vicious cycle of loosen, adjust, tighten, check, repeat until we've earned another gray hair.
Simplifying The Sprocket Alignment Procedure
Rolling the rear wheel, sometimes swiftly and other times gently, while checking that each tooth has some amount of space around it is a better way to insure proper chain/sprocket alignment. Another well known method is to measure from both sides of the center axle to an equidistant point near the motor before confirming both figures are identical. Our preference for the first option stems from the final drive employing so many moving parts.
This approach compensates for any wildcard behaviors that might find their way into the mix ...
There's reason for thinking that any shift, to the right or left, would be the correct choice when tuning your rear wheel's horizontal axis but actions speak louder than words. Noting the sprocket's teeth were resting left of my chain, I tightened in the right side alignment bolt in hopes that it would bring things center. Instead, my wheel became further misaligned and the more said adjustment was tweaked, the farther back I had to go to resolve matters.
Drive Chain And Rear Sprocket Trigonometry
Pictured above is my misaligned sprocket (left) and corrected alignment (right). Observe the visible space on either side of the sprocket's teeth. For double-sided swing arms, the gist of all things chain alignment can be summed in a simple phrase ....
Facing the back of the bike, backing out the alignment bolt on the right side of the swing arm moves the teeth of the rear sprocket to the right within the chain links.
Backtracking my steps to think about why the above statement would produce successful alignment gave me both answers and an awkward facial tick. One thing I learned is that my motorcycle chain is anchored more sturdily at the front sprocket. Over testing (exaggerating my chain's misalignment) confirmed the process reliable, now published here for future reference.
That stated, remember to take notes whenever executing a rare but recurring motorcycle maintenance task! More importantly, post your findings to this site by way of an article! Even if dancing the "two steps forward, one step back" tango, your properly maintained motorcycle and newfound knowledge will serve as reward.
What Technique Do You Use When Adjusting Your Motorcycle Chain?
We mention more than one approach above. How do you go about motorcycle chain alignment? How did you arrive at this method and why? Your input is invited. Post an article!