(From the J&P Cycles Blog Archive)

Every internal combustion engine in the world is a variation of an air pump. As the piston goes down with the valve open, air (mixed with fuel) rushes into the cylinder. The valve closes, the piston goes up, the air-fuel mixture is compressed, a spark occurs, POWER is made, and the spent gasses get sent merrily down the pipe. To make more power we need to get more air into and out of the motor.

Add a new air cleaner

The easiest place to start is with the air cleaner assembly. H-D is handcuffed by its compliance with the EPA. Since the stock airbox is very restrictive, we can let loose a few ponies by simply changing to a good quality air cleaner assembly like the Hypercharger from Küryakyn, Rinehart Racing's Inverted Moto Series Air Cleaner or an Arlen Ness Deep Cut Air Cleaner Kit.

These less restrictive air cleaners allow more air and fuel (more air requires more fuel) into the cylinder, giving us our power increase. Keep in mind that any time you change the airflow through an engine, the carburetor or electronic fuel injection (EFI) must be re-jetted or re-calibrated.

Upgrade Your Exhaust

This also holds true for our next topic, exhaust systems. Now that we are getting more air and fuel in, we have to be able to get more out.

I know that drag pipes are very popular but, in fact, on the street they actually hurt performance. They only work at the rpm they are turned for, and kill power everywhere else. This can be modified by adding baffles and reversion cones like the AR Power Cones, but even modified drag pipes are not as effective as other systems.

The best choice for making power is a two-into-one system like Vance & Hines Pro Pipes or Freedom Performance Union's 2-into-1 Exhaust System. If you don’t care for the looks of these styles, you can also get excellent results with the Python 3 series or with the exceptional offerings from Rinehart.

An interesting development in today’s exhaust technology is the double-wall construction of the new Double-D’s. These should be very blue-resistant. Exhaust “bluing,” by the way, is caused by improper jetting or timing. You can use a product called Blueaway to get rid of the blues, but it’s better to stop it up front with proper jetting and timing. A mixture too rich is as bad as one that’s too lean.

Swap Out Your Carb

If your wallet allows it, the next move would be a carburetor change. The stock carb on 1990 and up Evolution engines is a CV Keihin. Set up correctly, this is a good carb. But its outstanding low-end performance is offset by its small size and wimpy top-end pizzazz. It works well around town, but suffers in big freeway roll-ons. S&S has the cure, and it’s no wonder that their very complete Super E kit is one of J&P Cycles' bestselling products. Once again, more air going in equals more power. These American-made kits are very easy to install and come with an outstanding instruction booklet.

Another carb to consider is the Mikuni HSR42. A strong performer in its own right, it also has detailed instructions.

Mikuni HSR42

Both the Mikuni and S&S kits come with well-designed, free-flowing air cleaners. The traditional S&S teardrop was designed with a vane in the cover to increase air flow (and it’s attractive, too!). To improve the S&S kit, I recommend you replace the foam element with a K&N gauze-type element. The Mikuni ships with the K&N filter.

Add a Fuel Management System for EFI Motorcycles

Got EFI? There’s some good news for you injected guys, too. K&N, in conjunction with the fine folks at Dynojet, have developed something called the Power Commander. This little unit lets us easily make whatever tuning changes are needed after installing new pipes or tweaking the intake side. Well-engineered, this unit is infinitely adjustable and very user-friendly. Vance & Hines' Fuelpak is another excellent fuel management system that can be calibrated directly from your cell phone.

That wraps it up this time. We will continue our discussion in the next issue of Tech Talk.1.