There are several reasons you should tighten the chain on your dirt bike regularly, but a less-than-obvious reason is to prevent a major catastrophe. If you ask someone, “Why do you tighten the chain?” they’ll probably say that “It will get loose and fall off if you don’t,” or “To prevent chain slap.” While these reasons are true, because chains can and will fall off, as well as slap around and wear parts out, the deadliest result is not far off from a chain falling off the sprocket.
Think about what happens when the chain comes off… Does it just keep spinning freely? No. Either the chain guard catches it and the chain grinds on it, or the chain gets caulked and spins up to the counter-shaft sprocket then seizing it because there’s no room and cracks the case because there’s so much rotating mass. There goes the crankcase, tranny, and possibly more. All this because you forgot to take five minutes and tighten the chain…
The first thing to do if you haven’t already is wash the bike. A bike full of dirt, clay, oil, and other foreign materials makes it much harder to work on. Cleaning the chain will make it last longer, so a strong soap, and wire brush will do a good job. Next thing to do is set-the bike up in an open area of your garage on a stand so the rear wheel is off the ground.
So Easy, So Simple, Why Doesn’t Everyone Do It?
Once the bike is all ready and you have the tools, take a wrench (usually 1 1/16″) and loosen the nut on the left side of the axle so it turns with no tension. Next you break loose the lock nuts (10mm) that are up against the swing-arm on both sides. Then, on the left side, turn the adjusting bolt out with a wrench until the chain is tight enough (more on that later). The reason you want to do the left side first is because you are adjusting the chain. If you start with the right side then you may have to do multiple adjustments.
Proper chain slack should be 1 1/2 – 2” (38-50mm) at the end of the chain guide. A relatively accurate way to check is to put two fingers in between the chain and chain guide; it should be pressing on them if it’s tightened properly. After the chain is tightened to spec on the left side, do the same thing on the right side. There are marks on the axle blocks and swing-arm. Adjust the right side so that the notch is in the exact position as the left side is. Failure to do this will result in a wheel that doesn’t spin straight, which could cause damage or a crash.
Let ‘er Buck!
After you tighten the lock-nuts, then go ahead and tighten the axle nut. Spray some chain lube on the chain and you’re ready to roll! Just remember to look at and clean the chain on your dirt bike every single ride. This will help prevent major disasters, and the chain will have a longer life.