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The Run Down On Drive Belts


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Time To Loosen Your Belt

Nothing will ruin a good time like you’re rubber band breaking half way through your ride. Here are a few tips on maintenance for belts and pulleys.

First off, the rear belt isn’t actually a belt as in fan belt. It is a poly-chain, therefore you tighten it like a chain and not like a fan belt. The specification book calls for about 1/4-inch to 3/8-inch travel with about 10 ft-lbs of upward pressure from the bottom side of the belt. The ft-lb tensioning device also has to be fairly centralized between the front and rear pulleys. I noticed that the new twin-cam FL models have a little gauged window in the bottom belt guard that has notches to make this easy. Each notch is a 1/8-inch increment.

Things that can cause premature wear on belts are over tightening, sand, dirt, rocks etc. You guys that think it looks cool running an open rear belt are in for more headaches down the road, because that guard does a pretty good job of keeping most of the trash out from between the belt and rear pulley.

The point is, that even that stock bottom belt guard would only peel off only so much of that gumbo mud. Some of it got lodged it between my belt and pulleys. At first the mud would mash out evenly so I didn’t notice what was happening, but after the mud got hard-packed in the pulley teeth, some of it flew out, and some of it didn’t. It kind of felt like the trans was stripping a gear with the back and forth jerking. You get the same sensation when some of the teeth start peeling loose from the inside of the belt, except that is more intermittent.

Changing the belt involves a heck of lot of work. You have to remove the inner and outer primary and either a shock on the drive side, of the centerpiece of the swing arm on softail models. Eventually I learned that the trick is to keep the back wheel spinning fast enough to keep the mud slung off of the rear wheel.

Another thing poly-chains don’t like is extreme cold weather. Like I said, I had to ride to work in all kinds of weather. It seems the when the temperature reached below 20 degrees Fahrenheit, the belt teeth would tend to get brittle. Then comes that intermittent jerking sensation that I spoke of earlier.

Running your belt too loose will also cause the pulley teeth to wear faster. Most aftermarket pulleys have hard chrome plating over the aluminum, and once that wears off, the softer aluminum wears even faster. All it takes is on piece of gravel getting embedded in the pulley to chip out some of the chrome, and from there, it’s going to progress faster.

Every time you change out your rear tire, you should always inspect the pulleys for wear, along with checking the brake pads and repacking the wheel bearings. Checking the pulleys is easy. First, visually inspect the pulley for anything obvious. Then feel the inside valleys of the teeth to see if a ridge is starting to form on the side where the belt is putting the most pressure on when your riding. If you can feel that it’s starting to wallow out a little, you can either change it out, or keep this in mind and keep a closer eye on it.

Inspect the belt to make sure there isn’t any debris embedded in the belt teeth. This will turn the belt into a kind of grindstone that will wear out the pulleys faster too. The front pulley is a little more difficult to inspect, but however you can get to it, the same procedure goes for it. Use the belt to rotate it.

When you get the rear tire mounted, it is imperative that the pulleys be aligned with each other. There is a margin of error, but if it isn’t relatively close, one side of the pulley will wear faster than the other. By the same token, you don’t want to sacrifice the tracking of your rear tire in relation to the front, because that is definitely more important.

By comparison, a rear belt drive is more vibration free and less maintenance than a chain. That being said, I feel it is important to say that chains stretch unevenly, and sprockets wear. The teeth will slope over like a circular saw blade, and wear down to a nub. I’ve seen people get all they could get out of them. Chains have the same enemies as a belt drive, but the one the chain has that a belt doesn’t, is a master link. Make sure that the open end of the clip on the master link is facing opposite of the direction of rotation. Nothing like flying down the freeway and your chain comes apart because the clip popped off after hitting the chain guard .

HD has a heavy duty belt that you can use on a warmed over bagger if you have any problems with belt breakage, Part number 40130-03 is $40.00 more expensive than a stock one.

Here's a link with pics that will show what's involved to replace a drive belt...

Drive Belt Replacement - Harley Davidson Community