Recently, Kevin (the "K" in DK Custom) was asked how to increase performance on a stock Tri Glide; what upgrades, Stage I, II, III or Stage IV would be best, etc. Here is a quote from his response:

"I am on my 3rd Tri Glide now, and I have done the same thing to all three of them &  unless the guys I am riding with (2 or 3 wheels) cruise at better than 95 miles an hour, or race from stop light to stop light, I've always been able to stay with them.  In the twistys, none of them can keep up with me.  Most of them I can keep up with on fast acceleration from 30 mph to 75 mph, unless they have done similar mods to their bikes as I have done to my Trike.

If I am running with other Trikes, even ones that have had Harley Stage IV upgrades, I can typically stay right with them. 

This works with any Harley-Davidson & below we'll give you the details on why but here's the gist of his suggestion:


Before doing bigger upgrades to your Harley engine, building the best, most solid foundationFIRST, is key to performance. 

These are the 4 things, that when combined, give you that solid foundation, while also greatly increasing performance & engine longevity:

  1. Install a True High Flow A/C Intake
  2. Unclog the Exhaust
  3. Get a Good Tune
  4. Reduce Engine Heat


1. Install A True High Flow A/C Intake

A True High Flow Air Cleaner Intake is equipped with an External Breather System.

Regardless of what stage upgrade is done, it is important for clean, cool, oxygen rich air to get

into the combustion chambers. Not doing that will reduce performance and tune stability. See

for more info on that HERE.

Also, what happens to the air AFTER it passes thru the filter element is very important to performance. 

What the shape, contour and harmonics of the air cleaner INSIDE the filter element play a significant role in HOW the air flows and, thus, performance.


2. Unclog the Exhaust (How Harley Exhaust works...smashing the myths)

You do not want anything working against the engine, whether it be overly restrictive baffling or

reversion...both of those kill power. The key is having it flow out freely, with no reversion.

See more info on exhaust HERE.

FYI, for anyone who isn't wanting to piss off the neighbors, a good exhaust set up does not

have to be super loud. The Thunder Torque Inserts™ coupled with a free flowing slip-on that has significant sound-deadening packing, can be fairly quiet and still have good performance.  The Hi-Roller Slip-ons at this LINK are a good example.


3. Get A Good Tune


These bikes run entirely too lean (Twin Cams & Sportys) from the factory.  Even though M8's

are not overly lean from the factory (see Report on that HERE) they can still run better with and

improved tune. Getting a good tune with the current HD tuners is not possible. They are EPA

compliant and, by definition, hold the power back. With a good tune, your bike will run longer,

stronger, and more efficiently. Kevin uses the Power Vision. See a full Overview of Tuning Options HERE.


4. Reduce Engine Heat (How reducing heat increases Performance)

Heat reduction is a HUGE, MAJOR factor in power production. You can have two bikes that are exactly the same in every way, with the only difference that one is running at typical Harley temps, and the other is cooled down to optimum (or close to optimum) temps.  The difference in resulting power will be in the 15-25% range. See more details about controlling heat HERE.

By the way, Trike Owners, since the Trikes use the same engines as the Two-Wheel bikes, but

have so much more wind resistance, more weight, plus less air flowing past the engine (the

rears fender interrupt the air flow) they run even hotter than the two-wheelers.


It cannot be overstated how important it is to Performance & Engine Longevity to get these engines cooled down and running at the Optimum Temperatures, which is around 190* at the cylinder walls.


Better power and performance doesn't always mean a Stage IV. 

A bike with an Exceptional Stage I will usually keep up with a bike that has a Factory (mediocre) Stage IV.

A Free flowing air cleaner, free flowing exhaust, a good tune, and optimum engine temps will have you keeping up with the group! 


See Overview of Exceptional Stage I's HERE


Leave us your thoughts & comments below!