An important step we do when porting Banshee cylinders is to cut boost ports into the cylinders. These ports are also called Boyesen Ports, named after Ivan Boyesen who first patented this design . The ports improve intake area and improve performance by increasing crankcase filling. Adding the boost ports increases midrange and top end hp.
As shown we machine these ports on a milling machine to insure size angle and placement.
Porting the cylinder
Because acceleration is so important We concentrate on improving efficiency and improving scavenging in the cylinder. While it is true that long duration port timing can make a lot of horsepower, that type of engine is hard to ride and has a very narrow power band. We have found that controlling the fuel charge with proper transfer port design allows us to make the big horse power, but give the advantage of a much wider power band. Of course we improve the shapes of the exhaust and intake ports as well. Each cylinder is ported to meet the needs of the individual rider. LED porting is much more than a big tall exhaust port!
An important part of banshee porting is matching the center case transfer passages to the transfer duct entries on the bottom of the cylinders. Stock the cases a badly mismatched to the cylinders. The photo below on the left shows the scribe marks we have laid out to grind to the correct this mismatch. As you can see a lot of material will need to be removed. The photo below on the right show the cases after being port matched to the cylinders.
Because we often double the horse power on a 350 Banshee build the crank shaft needs attention also. We true the crank shaft so it runs true in the case. To much run out in the crank means that the shaft wobbles . This causes vibration friction and will eventually cause a failure of both e cases and the crankshaft. We then wield the crankpins to prevent the flywheels from moving on the crank pins. This helps keep the crank true and prevents twisting or spreading under hard use.
