Understanding the camshaft: how it works and which to choose

When you ask a motorist, he will tell you that motorcycles have a soul, their own personality.
If the heart of our engine is the oil pump, the lungs the cylinders and the brain the ignition switchboard then following this analogy the camshaft would be the character or personality.
This element is decisive and marks the behavior of our engine, since through its design the delivery of torque (and power) is defined. Para poner un ejemplo, si un motor tiene 100cv y le instalamos un árbol de levas diferente ésto no va a hacer que aumente la potencia, pero si que va a cambiar CÓMO y DÓNDE se entrega esta potencia, si esta entrega de potencia es progresiva y The maximum torque is obtained at low or half revolutions we will have an easy motorcycle in any march, with force and ideal to accelerate, travel and travel through the city. If, on the contrary, if the motor torque is delivered more concentrated and at the high revolutions we will have a more sporty and aggressive motorcycle, ideal to release adrenaline and hurry braking.

Cams
The function of the camshaft is to open and close the intake and exhaust valves of the butt, so it controls the filling and emptying of the cylinders.

It is a rotary element that has eccentric lobes (cams) that push the rods that move the valve train (as in the Big Twin models), or the valves directly (as in the V-ROD models).

Varying the shape of the cams to be installed and the main use that will be given to the vehicle.
There are engines with a single camshaft, such as Evolution or Milwaukee Eight,

With two trees, such as the Twin Cam (hence the name of this engine),

With three trees like the Indian Thunderstroke,

 or with four independent camshafts as in Sportster models ...

Compatibility with emissions
As almost all the elements of the engine the original camshaft is designed so that the engine works correctly within the current regulations, not to work optimally. It is therefore that with the replacement of this component with another of high performance we will optimize the entry and exit of air, instantly improving the general performance.

Technical characteristics
When selecting a camshaft from different manufacturers we must take into account its characteristics, which can be summarized in:

• Elevation or opening: Determine the height of the lobe and what the valve will rise from its seat.
• Duration: marked by the width of the lobe, indicates how long the open valve remains.
• Timing: Indicates when the valves open and close in relation to the position of the piston. 

A key fact that will tell us what "character" has a camshaft is the closure of the intake valve in relation to the lower dead point (ABDC). In general, it is less than 30º is a camshaft for low RPM, from 30º to 50º is a half -rank tree or for light motorcycles and with more than 50º we are already talking about optimization for high RPM, or very enhanced engines.

How to choose a camshaft
When replacing our camshaft there are 2 basic issues that should know:

• What is the main use of the motorcycle and driving style?

We can go in search of more sports sensations, to get a little more "joy" in the engine, or on the contrary we dedicate ourselves to traveling to gas, needing good acceleration and low RPM.

• What are the characteristics of the engine, and what other modifications have been made on the motorcycle?

You have to take into account the cubic, the type of chassis and brakes, compression and other engine potentiation factors so that the result obtained is satisfactory. It makes no sense to install a high RPM camshaft in a very large engine that cannot reach those revolutions, or install a very “crossed” camshaft (the admission and exhaust valves spend a lot of time open) in an engine where Admission and escape has not been optimized.

Final conclusions
As you could have verified the choice of camshaft is a complex and very important decision, since it will largely influence the behavior and sensations that the engine will transmit to us.
It is therefore essential to think about this component as another part of the set, which complements it, optimizes and enhances its main characteristics.

Frank Burguera

#mecanicaharley