Harley Davidson Dyna Glide: Performance Modifications

This article applies to Dyna Glide models (1991-2016).

While the Dyna is certainly no slouch in its stock form, there are a few things that can be done to increase the performance of your ride. Some of these things cost more than others, but all of them are well worth the time and money. If performance is something you are interested in, you are in the right place.

So You Want a Performance Dyna?

The Dyna is a very capable platform for a serious performance build. There are many shops and organizations pushing the Dyna to its limits. Some of these shops are San Diego Customs (who's "Oakland Ripper" project is picture below) and Unknown Industries. These guys are making huge power while keeping the Dynas reliable and durable enough to ride every day. They push these bikes to the limits of what is possible and are a model to be imitated for Dyna performance.

While the areas that performance can be improved in are nearly limitless, we will focus on the basics for this article. The three main areas to begin unlocking your Dyna's potential are exhaust, fuel delivery, and suspension. With a racing background, I prefer to upgrade suspension first on all of my vehicles. However, the general population tends to begin with exhaust, so we will start there and move on.

Free-Flowing Exhaust Systems

DIY Cost – $350-$1,200

Professional Cost – $500-$1,600

Skill Level – Easy; novice mechanics should be capable of installing most exhaust systems. There are only a few nuts, bolts, and two gaskets involved in the job.

Exhausts are often replaced for a better sound, but that is not why we are here. A free-flowing exhaust like the system from Royal-T Racing (pictured) increases the performance of your engine by up to 15%. Yes, these exhausts make the bike louder than stock, but often not as loud as a set of straight pipes with worse performance. Other great options include the almighty Thunderheader, Sawicki Speed, the D&D Fat Cat and the Vance and Hines Pro-Pipe.

While a traditional open 2-2 exhaust system may offer slightly better performance than the factory exhaust, a 2-1 is the only real option for performance. Just like with a race car, a motorcycle engine makes more power with optimum levels of back pressure because it will scavenge better. To provide better scavenging, a collector pipe is needed and a baffle is required for back pressure. By and large, a 2-1 pipe will make more power than a similar 2-2 option.

If you wish to learn more of the science behind the exhaust and how to choose the best pipe for your Dyna, visit RB Racing's website (link at the bottom).

Fuel Delivery Systems

DIY Cost – $2-$500

Professional Cost – $50-$750

Skill Level – Easy to Moderate; this varies from novice to expert, depending on the extent to which you modify your Dyna's fuel delivery.

The fuel delivery systems on Dyna Glides vary by year. If your Dyna is a 2005 or earlier, it is likely carbureted. If it is a 2006 or newer, it has an electronic fuel injection system. Certain people prefer certain systems, and I am no different. But for the sake of this argument, I will explain the modifications to both systems so that you can make the best decision for your motorcycle. Essentially, the goal is the same and that is to increase the fuel/air mixture to allow your engine to make more power efficiently.

If your motorcycle is carbureted, this is a fairly cheap venture. New jets cost less than a dollar at most independent shops and a total rebuild kit can be had for less than $20. The goal here is to chain the Main Jet, Slow Jet, and Needle Jet sizes in order to increase the amount of fuel delivered to match any increase in air from a less restrictive filter, or freer flowing exhaust. I do not recommend changing more than one size at a time at each position until you achieve desired results. The best results are usually found with a dyno tune be an expert shop, but if you learn to read spark plugs, you can make effective improvements, especially at the top end. The factory CV carburetor has been proven to be reliable and capable on motors making up to 105 HP. If you are making more than that, you should look into a carburetor from either Mikuni or S&S. These companies will work with you to provide you with a carburetor tuned specifically for your Dyna.

If you have electronic fuel injection, the process is entirely different. In order to change the air/fuel ratio, you will need a programmer/tuner like the DynoJet Power Commander. These tuners connect to your Dyna with an interface cable and download a new fuel map to your fuel delivery system. Often times, these maps can be downloaded for your specific modifications from the DynoJet website. This takes the guesswork out of it all and allows your bike to make more power easily.

Suspension

DIY Cost – $200-$2,500

Professional Cost – Varies greatly

Skill Level – Easy to Moderate; again, this varies based on the extent to which you decide to modify your suspension.

I suggest that the largest part of your performance budget be spent on suspension. The factory Dyna Glide suspension leaves much to be desired, but there is a reason for that. Suspension is not a "one size fits all" part. In order for your suspension to work efficiently, it must be matched to both the rider and the Dyna. Things like the weight of the rider and passenger, and the primary type of riding the Dyna does will factor in. Cheaper options like Progressive will be slightly better than stock, but they don't even begin to tap into what is possible. A quality pair of shocks like the Ohlins (pictured), Works, or Hagon Nitros will be valved and tuned specifically for your application. Most of these are rebuild-able, and can be adjusted if you gain weight, or change the bike from solo to 2-up riding. So when you order your suspension, you should do so over the phone or in person to get exactly what YOU need for YOUR Dyna.

Some factors that affect quality of suspension are spring rates, rebound rates, and dampening, as well as overall length and shock travel. A longer shock will give you a steeper fork rake, and offer an increased ride height, which allows for a better lean angle and therefore, significantly better performance in the twisties. This also makes your Dyna much safer for you and your passengers and instills confidence. I always say that the only people who understand the value of suspension on a motorcycle are those who have ridden a properly tuned suspension. This should be your first priority if you want to make your bike handle better, more comfortable, and safer.

Related Discussions and Site

• Dyna Handling Performance - HDForums.com
• Best Performing Dyna Exhaust - HDForums.com
• Idiots Guide to Carb Jetting - HDForums.com
• Advantages of Power Commander - HDForums.com
• Harley Exhaust System Design - RBRacing-rsr.com