Submitted by: abtech
First of all, I use a technique that I learned several years ago from a gentleman who knew much more than I when it came to working on your bike ("Pops" Yoshimura). The technique described here works great on the 929 or any other bike that has the same overall swingarm length when measured from the center of the swingarm pivot bolt to the end of the swingarm.
To adjust the chain, you will need the following tools:
1 each 32 mm socket wrench
1 each Torque wrench
2 each 12 mm open end wrench
1 each small "T" edge
1 each Rear Stand
Step 1
Put the bike up on the rear stand and clean the area around the rear axle and chain adjusters. Using the 32 mm socket wrench, loosen the rear axle nut until it is loose enough to move the axle in the swingarm slots by moving the rear wheel/tire.
Step 2
From the rear of the bike, grab the rear wheel and pull it back away from the engine. Sight down the chain to make certain the chain is approximately straight.
Using both 12 mm open end wrenches, loosen the chain adjuster lock nut (the one toward the front).
Step 3
On the chain (left) side of the bike, using one 12 mm open end wrench, turn the chain adjuster bolt (the one toward the rear) counter clockwise until the chain has approximately 1.75" of total slack when moved up and down below the swingarm. This is a rough measurement, as you now go to the other side and make the same approximate number of turns on the right side adjuster.
NOTE: When measuring chain slack, the idea is to measure the chain approximately mid way between the sprockets and measure the total distance when the chain is pushed toward the swingarm and pulled away from the swingarm. Use a link pin as a reference. When getting to your final adjustment, rotate the rear wheel and check the chain at it's loosest and tightest points, as the measured slack will change as the wheel is rotated.
Step 4 
Recheck the chain slack and adjust both sides until the chain again has approximately 1.75" of total slack. Now with the "T" edge, measure the chain (left) side from the rear of the swingarm to the adjuster block and then do the same on the right side, adjusting it to match the reading from the left. Measure the chain slack again and adjust as needed until both sides are exactly the same and the chain has roughly 1.75" total slack measured midway below the swingarm.
Step 5
Take the bike off of the stand and have someone sit on the bike and measure the slack again at its tightest and loosest points. Adjust both sides as required, making certain that your final adjustment is identical on both sides when measured with the "T" edge and the chain has no more than 2.0" total slack and no less than 1.6" total slack. Tighten the chain adjuster lock nuts with a 12 mm open end wrench while holding the adjuster bolt with the other 12 mm wrench. Make certain you don't "readjust" the bolts while tightening.
Place the bike back on the stand and torque the rear axle nut to 83 Ft Lbs. (113 N-m).