Changing and Adjusting Chain Tension

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The pre-ride sight check might delay your trip to the track or trails but catching issues before you head out can prevent lots of headaches later.

One of the most important visual checks is to your sprockets and chain. Quite often the first signs of wear shows up on the sprocket teeth. If you see this or wear to the chain it's time to replace. We recommend a complete replacement of your chain and sprockets regardless of whether one shows signs of wear and the other looks pretty good. Additionally, now is a good time to thoroughly check the chain guides and rollers for wear as well.

Changing the chain on your dirt bike is not a quick endeavor. But with experience it'll become less of a hassle and the process of changing out the chain is also useful to know for adjusting the chain's length as you've got to loosen the same parts in order to get at the chain. This article focuses on changing and adjusting the chain on your dirt bike. For further information on dirt bike gearing, check out The Ultimate Dirt Bike Sprocket and Gearing Guide.

How to Change a Chain

The first step is removing the old chain. This is the easiest part as all you have to do is remove the master link and the chain comes right off. Adding the new chain also involves the master link as you clasp that on once you've snaked it around the sprockets - and hopefully newsprockets if you're changing out an old, wore down chain.

Typically dirt bike chains come in 120 link lengths. You'll need a chain breaker if it requires an adjustment. What's more, as you ride the chain naturally stretches overtime so you'll need to adjust the sag every now and then which might require removing some links. So even if the out-of- the box chain fits, you'll want to invest in a chain breaker.

If you're working on an adjustment job to an existing chain now is a good time to clean and lube it. There's no need to remove the chain for cleaning and lubrication. Put your bike on a bike stand, clean the chain with a chain brush by slowly rotating the back tire manually and spray on lube using the same process. Keep fingers away from the sprockets and don't move the tire by starting the bike and putting it in gear.

Follow the directions below for the adjustment.

How to Adjust Chain Tension

When installing a new chain, size the chain with the wheel adjusted completely forward. This means tightening the chain adjuster bolts, that screw into the swingarm and butt-up against the axle blocks, completely inside the swingarm. To do this, unscrew the jamb nut the adjuster bolt feeds into and screw in the bolts. Be sure to do this on both sides.

The chain adjuster bolts are a little tricky to get at

When loosening or tightening the chain adjuster bolts you'll need an open-ended wrench. Use the CORRECT wrench size or you'll round off the bolt head, then it's off to a mechanic. The jamb nut is usually 12mm the bolts are 8mm or 10mm.

Now, measure the new chain off the rear sprocket to determine how many links to cut. The rule of thumb on chain sag is you want two to three fingers of slack but the owner's manual should give you the correct number for the make and model of your dirt bike.

Place your fingers vertically, underneath the chain, on the plastic rub plate on top of the swing arm. The chain should drape nicely across the top of your index finger without additional drooping. If you're lucky removing links or cutting the chain is enough otherwise you'll need to fine tune the chain tension.

Check the chain tension

Whether it's a new chain or a stretched existing chain, this is accomplished by moving the rear axle backward. Loosen or "unscrew" the chain adjuster bolts until you get the correct chain tension using the finger test as noted above. This action moves the axle backwards thus tightening the chain.

If the chain feels tight against your fingers then it's too tight which can cause engine and transmission damage so you'll need to slide the axle forward. This is done by tightening or "screwing in" the chain adjuster bolts. Out of the box, a new chain won't be too tight.

Indented lines or tick marks on the swingarm along with corresponding numbers (or more tick marks) on the axle blocks provide a visual reference for adjusting both sides equally. Once you've made the appropriate adjustments tighten the chain adjuster jamb nut and the axle bolt. Double check the chain tension before loading up the truck.

The axle bolt is on the right side of the rear tire

As your chain continues to stretch you'll always adjust the sag by moving the axle back. Once you've run out of room then it's time for a new chain even if it shows no signs of wear.