HOW TO: Chain Adjustment
Some of us are receiving our 675's with chains that are WAY out of the 35-40mm specification after the first couple of miles have been accumulated.
Although many may find that chain adjustment may be below the "How To" need, I have noticed that the owner's manual mentions how to adjust the chain, but doesn’t do a very good job of it.
Specifically, they list the following (quoted from the owner’s manual):
“Place the motorcycle on a level surface and hold it in an upright position with no weight on it. Rotate the rear wheel by pushing the motorcycle to find the position where the chain is tightest, and measure the vertical movement of the chain midway between the sprockets. The vertical movement of the drive chain must be in the range 1.38-1.57in (35-40mm).”
Ok, now think about that for a moment. One hand holds the bike up. One hand holds the measuring device. One hand moves the chain.... WAIT! I’ve run out of hands!!
For that reason, I submit the following.
Tools you will need:
1. 27mm Socket and means to turn it. Unfortunately there is not enough room between the swingarm and the nut to fit a wrench in there. You will need to use a socket.
2. 13mm wrench. This is used to loosen the locknut on the adjuster.
3. 12mm wrench. Used to turn the adjuster.
4. Measuring device, preferably in metric increments.
Note: Although you will see that the bike illustrated here is supported by a swingarm stand, you really do not need to have one. It does make it easier, however. If you have an associate who can hold the bike upright while you make the adjustments, that would be adequate. Doing this job without a swingarm stand or the help of someone else would be difficult. One reason why the bike must be vertical is to eliminate side loads on the rear wheel that would prevent the wheel from being aligned correctly when re-tightened.
Running with a loose chain runs the risk of the chain “hopping” teeth or slipping off entirely. Running with a chain that is too tight will prohibit the suspension from traveling its designed distance, will wear out much more quickly, and will require more energy from the engine to turn it. As the suspension compresses, the distance from the front sprocket to the rear sprocket increases. Manufacturers know this increase and express it as vertical movement “at rest”.
Let’s get started...
1. The first thing to do is to determine whether or not you need to make an adjustment! So lets get to measuring. To take the measurement, you do not need to have the bike vertical. You will need to find where the chain is the tightest, and to do this you will need to rotate the wheel. Place the ruler at the midspan point between the front and rear sprockets. As you rotate the chain, note the distance the chain is from the swingarm. This measurement can be taken at either the top of the chain, top of the pin, center of the pin, bottom of the pin, or bottom of the chain. The point is that the specific PLACE is not important, but that the minimum distance is. The minimum distance signifies where the chain is the tightest. THIS is where you want to make your “play” measurement. In the following picture, the ruler reads “65mm” to the center of a pin.
2. Once you’ve found the tightest spot in the chain, you will then need to get the slop out of the TOP of the chain, such that when you make your slack measurement at the bottom of the chain, you’ll get an accurate reading. To facilitate this, put the bike in gear (any) and then either use a strap (as depicted in the pictures) to put tension on the wheel in a “backwards” direction (if on a stand) or position the bike uphill such that gravity will provide the needed tension.
3. Push chain upwards with your finger while holding the ruler and measure to the same point on the chain that you did in step 1. In this example, the ruler reads “30mm”. The difference is 35mm, which is the minimum specification, so no adjustment is needed. (In truth, this is an “after” picture.) If your measurement is between 35-40mm, no further action is needed. Go ahead and ride on! If your measurement is in excess of 40mm... you’ve got a bit more work ahead of you. Read on.
4. So your slack is out of specifications... don’t sweat it, it isn’t that difficult to adjust. Here is where you’re going to need the bike straight up, so enlist help or use a swingarm stand. Start by loosening the 27mm axlenut using your socket. Only loosen it enough that the washer behind it can spin. (You don’t need major looseness here.)
5. Loosen the locknuts on both sides of the swingarm with your 13mm wrench. You may want to hold the adjuster bolt with your 12mm to prevent it from rotating also while you loosen the locknut. (In this picture, the locknut has already been loosened.)
6. Carefully rotate the adjuster bolts with your 12mm wrench the same amount on each side to move the wheel forward or backward to either add or reduce slack in the chain. It does not take much movement of the wheel to make a big difference in slack, so go with small changes. I recommend that you count the “flats” of the bolthead. (A hexagon has six sides or “flats”). In the above picture, you can see that the adjuster bolt has a “flat” up, or parallel to the ground. Keep in mind that you’re moving both sides either clockwise or counter(anti)clockwise so the wrench will be moving up on one side and down on the other.
7. Retighten the locknuts with the 13mm wrench by holding the adjuster bolts still with the 12mm wrench. Retighten the axle nut by using the 27mm socket and by PUSHING FORWARD as depicted in the picture. This ensures that the axle is snug up against the adjusters and won’t “move forward” (out of adjustment) the first time you crack open the throttle. This is also the most important time to have the bike straight so that you don’t tighten down the axle while there’s a side load on the wheel.
8. Remeasure the slack as directed in steps 1-3.
9. Like shampoo, repeat as necessary.
*** Author assumes no liability for accuracy of information contained within as it is provided "informational" in nature. Author assumes no liability for differences between photo'd 675 and your own. Author assumes no responsibility if tighten up your chain to the point that if you hit a bump it will snap and then wrap itself around your rear wheel and you crash. Perform this work at your own risk.