The real power is in the heads with the right combination of cam, carb, and exhaust system.  We can bore the cases to make a bigger motor out of it, and we can always stroke them, that’s the easy way to get more power.  We use quality S&S parts and can build any size engine you want.  You can end up with a good dependable 95ci or 98ci motor.  To use new and improved power, you will need a high performance ignition system, balanced to the other performance upgrades.

Over-boring the 88ci to a 95ci may not leave you enough metal in the cylinders and they could get hot which can cause the cylinder to distort.  We recommend replacing the 88ci cylinders with stock 95ci cylinders to start with, in the long run you will be happier with the engine.

For example, if you’re going from stock Dyna bars to ape-hangers.  You will need to extent out all of your cables and lines.  Some manufacturers will tell you what new bars will require you to change out your control cables.  You also need to take into consideration cable length when changing risers.

Check your tire pressure once a week, and stay within the guidelines on the sidewall of the tires.  Change tires when they get down to 3/32 of an inch of tread.  If you are an average rider, no burnouts and such.  You should get about 6,000 miles on a rear tire, and about 8,000 miles on a front tire.    Another rule of thumb is two rears to one front.  Most people run tires too long.

In a Twin-Cam you may notice blow-by at the breather, which leaves traces of oil down the side of your bike, usually of the heat shields of your exhaust and on the oil bag. The reason for this is, even with the standard petroleum base oil, the scavenger side of the oil pump is marginal for the motor. The oil pump cannot sump the oil out from the bottom end quick enough which causes it to load up in the top end and flow out the breather. Your local shop can correct this by installing a Fueling Twin-Cam oiling pump.

There is more than one way to get your feet flat on the ground. There are shorter shocks for swing arm styles and several lowering kits for softails. Another way is the seat. There are many styles of seats on the market. If you choose a seat with narrower and lower profiles, you can get your feet up to two inches closer to the ground. Gel seats are also available so you don’t have to trade comfort for cool. Then there are tires. Pick a tire with a little lower and wider profile and gain down to one inch or more.

If you are going to switch to synthetic oil you should first establish your break-in miles, somewhere around 2,500 miles. In the engine we recommend 20/60 weight high-grade synthetic oil. Some recommend 20/50 weight for all three lubrication sections of the motorcycle, but we feel it does not have adequate shear strength to protect contacting surfaces in the transmission and primary. When running synthetics you may experience oil seeps in gasket areas, this is especially common to a bike with more than break-in miles on it.

The box stock Harley-Davidson® engine is built for longevity, not for peak performance, said Tom Doggett of Strokers USA, Inc. Harley de-tunes the Evolution engine by making the head ports less efficient. Doggett said he can increase the engine’s fuel efficiency and boost its horsepower by porting and decking the heads.

During the interview, for this Tech Tip, Doggett, a factory-certified Harley-Davidson® Master of Technologies, talked about laminar flow, boundary layers, and experimental wings on Navy jet aircraft. There is a tremendous amount of art and science involved in making large volumes of air move were you want it to go. Proper porting increases the flow of air from the carburetor through the head and out the exhaust pipe.

Air flows fastest along a straight line, it slows when it turns and slows dramatically when it hits a sharp bend. Porting removes some of the obstacles in air’s path by smoothing the rough edges inside the intake and exhaust passages in the heads. 

Doggett removes the lip around the valve seat and casting flaws. He also rounds out the corners in the air passages.

After reshaping the intake and exhaust ports, Doggett uses a fine polishing compound to apply a mirror finish to the exhaust port and combustion chamber. The polished surface resists the build up of carbon deposits. Carbon is a byproduct of the burning of gasoline. It sticks to the combustion chamber in the head and to the exhaust port. This clogs the hole and restricts the outward flow of hot exhaust gases—losing efficiency. 

Surprisingly, Doggett does not polish the intake port. A rough surface keeps the gasoline- rich air from sticking to the intake wall. If the port was polished, fuel droplets would puddle along the wall and would not burn efficiently in the combustion chamber. 

To further improve the performance potential of the stock Harley cylinder head, Doggett shaves approximately 40 thousandths of an inch (.040”) from the gasket surface with a milling machine. This process, called decking, will raise the stock 9 to 1 compression ratio to 10 to 1. The compression ratio is the amount the rising piston will squeeze the air and fuel inside the combustion chamber. 

“The tighter you squeeze the air mixture, the more horsepower you get out of it,” Doggett said. Of course when you increase the compression ratio, you must use a higher-octane gasoline. There are practical limits to increasing compression.

Doggett said, “The best thing to do, performance wise, is to alter the heads.” After porting the heads to increase horsepower and performance on a Harley, a hotter cam and carburetor can be installed to move more fuel/air into the combustion chamber. Doggett will also port the intake manifold to match the heads. A good ignition and tuned exhaust system completes the package. Doggett recommends the 2 into 1 Thunderheader exhaust system. “It’s not pretty, but it works pretty well,” Doggett said. A pair of drag pipes actually robs horsepower from the engine. 

Strokers USA, Inc. can turn around a pair of heads within a week. 

Some facts about heads:

In a naturally aspirated engine (no blower, no turbo), air is pushed into the head at 14.7 pounds per square inch (PSI) at sea level. 

The intake port and valve are larger than the exhaust valve and port because the exhaust only needs to flow 80 percent of the intake, due to the fact that exhaust gasses are forced out of the head at 1,600 to 1,800 PSI.

Freshening up the top ends of Evo’s will give you back your stock engine efficiency and power.  Over-boring cylinders depends on how much wear you have in the cylinders and how big a motor you want when you are done with the work.  When considering over-sizing a stock cylinder, you can maintain a cooler running big-inch motor with performance cylinders.  Performance cylinders are recommended when building a performance motor.  The more metal you have in the cylinders the more heat they can absorb and the less chance you have of over-heating.  

All of the cylinder work is done in house at Strokers USA, with SUNNED LBN 1660 honing machines and a Bridgeport boring machine.  All machine work is done in Lander, Wyoming with a normal three to five day turn-around, and Strokers USA will ship anywhere, anytime.” All work is guaranteed.