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H-D Pre-2004 Sportster Vibration: How to Deal With It

By Chuck Hawks


I really like the XL Sportster. The 2004 and later models, with their rubber isolated engines, have pretty well licked the vibration problem that plagued Sportsters from 1958 through 2003. However, how ahout riders with pre-2004 Evolution Sportsters?

I particularly like the powerful 1200cc Sportsters. Sportsters are quite versatile and are an awful lot of fun to ride, but pre-2004 XL's are not good bikes for long trips at freeway speeds, due to the vibration that makes itself evident somewhere between 60 and 70 MPH (depending on the individual bike and the rider's tolerance). This vibration comes from the solidly mounted engine/transmission unit. It is usually felt most in the handlebars and to a lesser extent in the footpegs.

Any pre-2004 Sportster, and especially a 1200, does vibrate when you run much above 3000 rpm in 5th gear. I don't know how to eliminate that. However, there are things you can do to control the vibration. Following are some approaches that usually work.

883cc or 1200cc

One point that is worth making at the outset is that typically an 883cc Sportster vibrates less than a 1200cc model. While I appreciate the performance of the various 1200 Sportsters, if you intend to tour on a Sportster and ride solo, consider an 883 unless you feel you really need the extra power of the 1200cc motor.

Taller gearing

Probably the most effective thing you can do to reduce vibration at cruising speed is to change to taller gearing. This is accomplished by changing one or both of the belt drive pulleys (or sprockets on chain driven bikes). While this does not eliminate the vibration, you can increase the speed at which you cruise before vibration becomes annoying. The examples in this section apply specifically to 5-speed, belt driven Sportsters, but the principle remains the same for XL's with 4-speed transmissions and/or chain drive. Hot XL magazine (now defunct) published a good article on Sportster gearing, which included gear charts for all Sportsters, in the Spring 1998 issue. I used the numbers from their gear charts in the examples that follow.

To ascertain the gearing you need, first take a test ride and note the rpm range where the bike cruises smoothly in 5th (top) gear. (Your bike must have a tachometer to do this. If it didn't come with a tach, now is the time to get one installed.) Then, using a gear chart, you can select the belt sprockets that will move the speed you want to cruise at into the rpm range you find tolerable.

The last I heard, H-D used 27- and 29-tooth tranny (front) pulleys. The 883 Sportys come with 27-tooth pulleys and the 1200's come with 29-tooth pulleys. The larger the transmission pulley, the taller the gearing; also, the smaller the rear pulley the taller the gearing. I believe all Sportsters come with 61-tooth rear pulleys. H-D offers a 55-tooth rear pulley as an option. Check to see what pulleys your bike is running at the present time, then use a gear chart to decide what pulleys you should be using.

If you stick with H-D pulleys, your choices are limited to 27 or 29-tooth in front and 55 or 61-tooth in the back. Usually, those are all you need. A company called Supermax Products offers 27, 28 and 29-tooth front pulleys, and 58, 61, 66 and 68-tooth rear pulleys.

For example, let's say that I want to be able to cruise at 65 MPH. Like most 883's (and 883/1200's), my Sportster came with 27-tooth front and 61-tooth rear pulleys. With those pulleys the engine turns 2700 rpm at 55 MPH, 3150 rpm at 65 MPH, and a whopping 3650 rpm at 75 MPH. I have done the test ride suggested above and determined that the bike cruises with acceptable smoothness (to me) between 2500 and 3100 rpm. At 65 MPH my bike is turning 3150 rpm and the vibration is beginning to become uncomfortable. By changing to the larger 29-tooth tranny pulley, I can drop the rpm at 65 MPH to 2950, which is within my comfort zone. If I wanted to cruise at 70 MPH, I would have to go to the 55-tooth rear pulley, but I could keep my 27-tooth front pulley. With that combination my engine would turn 2850 rpm at 65 MPH and 3075 rpm at 70 MPH. To cruise any faster, I will need to go to the 29-tooth front pulley, as well as the 55 tooth rear pulley (see the next example below).

If a Sportster has 29-tooth front and 61-tooth rear belt pulleys, like most stock 1200's, the engine will be turning 2500 rpm at 55 MPH, 2950 rpm at 65 MPH and 3400 rpm at 75 MPH. Change to a 55-tooth rear pulley, keeping the 29-tooth front pulley, and the engine will be turning 2250 rpm at 55 MPH, 2650 rpm at 65 MPH, and 3050 rpm at 75 mph. This combination should allow for cruising at 65-75 MPH in reasonable comfort.

The last two paragraphs illustrate the possibilities using H-D belt pulleys. Other combinations are possible using Supermax pulleys, but none will give higher cruising speeds with acceptable vibration than the 29-tooth front and 55-tooth rear combination illustrated above.

Bear in mind that by going to taller gearing your bike will not pull as hard off the line. Fortunately, Sportsters have a lot of low-end torque. You will probably need to downshift to pass quickly. On the other hand, gas mileage will increase. A buddy of mine averaged 63 miles per gallon on a 2,000 mile trip riding his 883 with tall gearing. For the person who tours on a Sportster, taller gearing is the hot set-up to quell vibration.

Fisher Vibration Damper

There is a device called the Fisher Vibration Damper, from Doug Fisher International (DFI). It is not cheap and is kind of a pain to install, as it replaces the stock engine sprocket and requires removing the clutch. It is supposed to let you cruise about 10 MPH faster before vibration becomes a problem. The Vibration Damper doesn't sacrifice punch off the line, as taller gearing does. The one article I read about the device (in Hot XL magazine) said it worked. Combine one of these with taller gearing to have a really smooth Sportster!

Handlebars, bar end weights, etc.

The handlebars are where riders generally find XL vibration most irritating at high cruising speeds. Vibration is due to the motor and not the fault of the handlebars, whatever their shape. However, other factors being equal, the longer the handlebar, the greater the amplitude of the vibration. At the same time, the frequency tends to be lower. The reverse is usually true for shorter handlebars. In my experience, risers tend to increase the vibration of any given handlebar. Handlebars of standard bend (like the bars that come stock on the XLH 883) seem to minimize vibration as well as, or better than, most other styles.

I have tried handlebar end weights and found that they help to a limited extent on some bikes (like "R" class BMW's or Buells). I have not tried them on a Sportster, but they are unlikely to hurt anything and might help to some extent. Certainly I would prefer bar end weights to filling the handlebars with something (see next paragraph).

As to filling the handlebar to dampen vibration, it helps, but adds a lot of weight. If you are going to go that route, it is best to use lead shot (birdshot). It's inexpensive, won't rust, doesn't rattle nearly as much as some alternatives (like steel BB's), works well and will pack tight. You can get lead shot at almost any gun shop, or anyplace that sells reloading supplies. Use small birdshot, such as #8. However, lead shot adds a lot of weight to the front end. Avoid inferior alternatives like sand or steel BB's. I'd experiment with bar end weights first and pack the bars as a last resort.

Footpegs

Use the stock anti-vibration footpegs that come on most Sportsters. The stock units are thick, soft and help absorb unwanted vibration that otherwise might put your feet to sleep. Forgo the more stylish chrome or billet replacement pegs. All of them vibrate more than the stock pegs.

Seats

Replace the stock seat. Most XL owners do this as a matter of course, since almost all Sportster models come with functionally impaired seats. For cruising at sustained high speeds a thick, heavily padded, touring type seat will isolate your butt from vibration better than the stock seat or a more stylish sport seat. H-D offers decent touring seats at a fair price.

Handgrips

Get cushion grips. The stock grips are not bad and they are better than most of the chromed or billet types, but soft touring grips are better yet. The grips are where your hands come into direct contact with the bikes worst vibration, so it makes sense to get soft ones.

Conclusion

The upshot of all of this is, while a stock pre-2004 Sportster is not a particularly good choice for sustained cruising at freeway speeds, there are remedies available. A good friend of mine set up his XLH 883 for a 24-hour/1000 mile Iron Butt ride employing many of the modifications discussed in this article and the result was very successful. His XL now proudly displays a license plate frame that reads: "Iron Butt Association--World's Toughest Riders."




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Copyright 2001, 2013 by Chuck Hawks. All rights reserved.


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