Aug. 3, 2016 | By Jeff King
With proper care, drive belts can last significantly longer than drive chains, potentially for the life of the bike. Regular inspections of the belt’s condition and ensuring that it has the correct amount of deflection (tension) play pivotal roles in the life of the belt and also to the other drive train components on your motorcycle.
Kevlar drive belts have several advantages over traditional chain drives or shafts. To start, drive belts won’t rust and do not require lubrication. Drive belts are highly efficient in transmitting power to the rear wheel, usually at 95 to 98 per cent efficiency. Additionally, belts are also lighter and quieter than a metal drive chain.
Inspect for Wear and Proper Deflection
Regularly inspecting the drive belt and ensuring that it has the correct amount of deflection is important to the life of the belt and to the other drive train components on your motorcycle.
The first step is to jack the bike up off the ground so the rear wheel is able to spin freely. Rotate the rear wheel by hand and visually inspect the inside of the belt for missing teeth, deep cuts or any signs of fraying. Small chips and surface cracks can be okay and do not necessarily require belt replacement. Take care to monitor these small imperfections making sure they do not worsen over time. If you have any doubts, get your belt looked at by a professional.
Inspect the outside of the belt as well, looking for fraying, cracks or holes. A belt that is missing teeth or is misaligned runs the risk of jumping teeth on the rear sprocket.
Holes can be caused by small rocks getting caught up in the belt and puncturing through.
Small holes like this one are usually not a big issue, although they need to be monitored over time to make sure they do not worsen.
Visually inspect the rear sprocket as well. Are the teeth in good shape? Small imperfections are usually ok, but if you find anything egregious, best to take it to your local mechanic for a second opinion.
Belt Drive Tension Adjustment
First off, make sure the bike is cool. Measuring the belt deflection with a warm belt will give inaccurate results. Put the bike back on the ground, either held vertically or on its kickstand. The full weight of the motorcycle should be on the rear wheel when measurements are taken and adjustments are made.
Consult the bike’s service manual, as deflection specifications vary from bike to bike. Typically, the service manual will note the range of adjustment in inches (ex: 7/8" to 1 1/4"). Adjusting your belt’s tension within the specified range is the goal.
We have a specialized belt tension gauge to take these measurements. This gauge helps you apply the correct amount of pressure to the belt to accurately measure the belt’s deflection. The marks on the tool are in 1/8" of an inch.
You’ll want to measure the deflection at a distance approximately in between the front and rear sprockets. Make sure and measure the deflection at several points on the belt to find the tightest section, and adjust tension there.
Place the tensioning tool on the belt maintaining a 90-degree angle and with zero tension on the gauge, using a reference point on the bike (bottom of the belt guard), and note where the zero tension mark is on the gauge.
Push up on the gauge until the 10-pound pressure mark meets the bottom of the tube.
The difference from your zero tension measurement and your final measurement (with 10 pounds of pressure applied) is your total deflection.
If you are within specs, sweet! You are done! If the measured deflection falls outside your manuals specifications, we have some adjusting to do.
Belt tension is adjusted by moving the rear axle either forward or back to achieve the correct deflection. Moving the rear axle back will increase deflection; moving the axle forward will reduce deflection. Take a second to think about what direction you need to move the axle to achieve the desired change in tension. It is easy to get mixed up and adjust yourself in circles.
Again, make sure your bike is on the ground for all your adjustments and measurements.
First step is to loosen the rear axle bolt ... not too loose ... finger tight is perfect. We want the axle just loose enough to allow movement by the adjusters, not much more.
The mechanical arrangements to adjust the rear axle vary from bike to bike, but an adjuster bolt and locknut arrangement is the most common.
Loosen the locknuts on both sides of the axle adjuster bolts. Back the locknuts off a bit so you have room to make your adjustments.
Again, think about what you want to achieve with your adjustments. To increase the belt tension, you’ll want to move the axle back. To reduce tension you’ll be moving the axle forward with the adjusters.
Using a wrench on the adjuster bolt, start with small adjustments, making sure to adjust both adjusters evenly. In addition to our goal of attaining the correct belt tension, we also want to make sure both sides are adjusted evenly so the belt tracks correctly and the rear axle remains perpendicular to the swingarm.
Again, make small adjustments and recheck your belt deflection after each adjustment. You’ll be surprised at how a little adjustment goes a long way in making a big difference in the belt’s tension.
When you have achieved the correct belt deflection, using a pair of wrenches, hold each adjuster bolt in position and snug up the locknuts on both sides. Tighten your axle nut to the specification listed in the service manual and recheck your deflection and axle alignment. Sometimes things can change when the axle is tightened up, so it’s best to check once more to make sure you are within spec and properly aligned.
If everything is tightened up, your deflection measures within specs and the axle is perpendicular … nice work! You’ve certainly earned a frosty beverage of your choice!
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DISCLAIMER: The methods in this article are guidelines, provided and performed by a trained mechanic. If you are not comfortable performing routine maintenance on your bike, it is recommended you get a trained mechanic to complete these and more difficult tasks on your bike.
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