Chain Adjustment + Wheel Alignment
OK, so you've used the marks on your swingarm to adjust your chain and align the wheels. You're all set, you think. Not necessarily. A closer look at adjusting your chain and aligning the wheels could save you some bucks and improve your bike's handling.
Have you ever wondered why, when you take your hands off the handlebar for a moment, your bike suddenly swoops off to one side like it had a date with the curb? Do your chain adjustments not last as long as you think they should? Perhaps the chain tightens up on you? Does it sometimes get loose quickly and then stay much the same for a long time? Ever wonder whether you should check the chain tension on or off the stand? Chain tight in one spot and loose in another?
Unfortunately, your owner's manual is of little use in answering these questions, since the factory assumes that its engineers are infallible, that everything wears evenly, that you always lube your chain at regular intervals and that you never ride in the rain. Their instructions for chain adjustment and wheel alignment are, as a consequence, inadequate.
Let's start by examining the kamikaze-into-the-curb syndrome. There are two possible reasons for this. One is that the motorcycle has been built with a weight bias to one side. However, more likely the wheels are out of alignment.
If the rear wheel is perfectly adjusted to the alignment marks on the swing arm, how can it possibly be out of alignment? First, the swingarm could have been welded together inaccurately at the factory. The marks are usually cast into the rear portion of the swingarm, and the whole assembly welded up in a jig by automatic welders. The swingarm is then mounted in a frame which is also a collection of pieces supposedly welded up perfectly.
Manufacturing tolerances are pretty good these days, but it's common to find small inaccuracies in this assembly, and any deviation alters wheel alignment. A few bikes are out as much as a whole adjustment mark, but most are out a much smaller amount. However, being out even as little as one-eighth of a notch can affect the handling of a motorcycle, and increase tire and chain wear.
Manufacturing and assembly tolerances require clearance between the axle and the adjusters, and this play can be excessive, causing a problem in retaining adjustment as well as alignment.
The key to overcoming all these inaccuracies and problems is to determine the correct wheel alignment and correct any inaccuracies in the marks, and then use a consistent method of adjustment that is easily repeatable.
Consistency is the most important aspect of chain adjustment. Always lube your chain thoroughly before adjusting, as lubing may change the tension. Use a quality chain lubricant, not motor oil, since chain lube goes on thinly to penetrate the chain and thickens into a sticky grease. The best time for lubrication is at the end of a ride when the chain is warm. The heat aids penetration of the lube into the bushings inside the chain.
Wheel alignment need only be checked once, and new marks made on the swingarm. After that, alignment can be made with respect to the new marks. There are a lot of horror stories around about using miles of string or long straight boards and spacers and hours of work, but it's not really necessary. You can tell by eye whether or not the wheels are straight. About six feet behind and about three or four inches off the ground is the best place to look from. Get a friend to help with turning the front wheel until it's in line with the rear wheel. Sighting down the side of the rear tire will quickly tell you if the rear end is cocked to one side. Moving the rear wheel in the appropriate direction will soon allow you to see both sides of the front wheel. With a little patience, you'll be amazed at how easy it is to get the rear wheel lined up with the front.
When you're sure that the wheels are in line, check the alignment marks on the adjusters. If. they are the same on both sides, you're lucky. If not, assume the chain side is correct and make a new reference mark on the other side of the swingarm. You won't have to check alignment again if you use this mark and tighten the axle correctly.
To adjust the chain as accurately as possible, put the bike on the centerÂstand, or a box if your bike has no stand. Spin the rear wheel slowly and check the chain tension as the wheel turns. Note that the chain tension varies. On some bikes you get a lot of variance. This variance is caused by uneven chain stretch (remember when you dropped the clutch at 11,000 rpm?) and eccentric sprockets.
This is also a good time to check the chain for wear. Regardless of adjustment, pull one of the chain links off the rear sprocket. If the chain lifts off the sprocket more than half the height of a tooth of the sprocket, the chain is worn out. Replace it right away and you won't have to replace the sprockets as well. Sprockets must be replaced when the teeth show signs of hooking, or a difference in profile between the back and front of the tooth. Never put a new chain on a hooked sprocket.
Find the tightest point in the chain and mark the wheel where it would touch the ground as a reference mark. The biggest problem in setting chain tension is determining where in the wheel's travel to check it. The correct point to check it is where the chain is tightest. This occurs when the front sprocket, swingarm pivot, and rear axle are in line. The surest way of checking this is to remove the rear shocks and lift the rear wheel up until it is in position, supporting it with blocks underneath or straps tied to the seat. Don't guess at the position of the front sprocket. Remove the cover and be sure. Position the reference mark on the tire facing down so that the chain is at its tightest point. Correct chain tension at this point is approximately one-half inch of play. (12-15mm)
Loosen the axle slightly, and using the adjuster bolts draw the wheel back until the chain is correctly adjusted. If you have to move the wheel forward, loosen the axle a little more as well as the adjusters and give the wheel a good kick forward. Try to move the wheel forward a little too much so that you draw the wheel back with the adjusters, thus eliminating any clearance problems in the adjusters.
You don't want to have to remove your shocks every time your chain needs adjusting so an easily repeatable method is needed. First, with the bike on its centerstand ensure that the reference mark on the tire is facing down so that the chain is at its tightest point. Note that the slack will be more than half an inch since the front sprocket, swingarm pivot and rear axle are no longer in line, but you should be able to find a reference point that allows easy adjustment. For example, on bike A, if you lift the top run of the chain at the passenger peg, your finger will just touch the chain guard. Since you just set the chain slack to one-half inch with the shocks removed, this reference should give you an easy, quick method of checking chain tension. Experiment to find your own reference point.
The first adjustment will probably take you an hour or so, but the next time it should only take a few minutes, and you'll have the satisfaction of knowing that it's right and your wheels are in line. The adjustment will also last longer, and so will the chain.