Pre-2004 H-D 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. But 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. However, 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, and 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. But there are things you can do to control the vibration. Below are some approaches that usually work.
The 883 Sportster
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- and 29-tooth in front, and 55- and 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.) And 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
Handlebars, bar end weights, etc.
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 works to some extent, 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 near 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 (I'd use #6, #7 1/2, or #8 shot). But lead shot does add 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.
Copyright 2001, 2005 by Chuck Hawks. All rights reserved.