All about the camshaft on Harley-Davidson motorcycles

On numerous occasions we hear about this internal engine element, which is one of the great strangers in terms of its characteristics. The camshaft is not an element that is usually replaced when improving the Custom motorcycle engine, probably due to the ignorance of real changes in engine behavior after replacement.
We will explain the basic points about its operation so that with the appropriate information you can decide if you are interested in changing your original camshaft for another high performance.

The camshaft function
This element is in charge of opening and closing the valves at the right time so that the 4 motor times occur: admission, compression, explosion and escape.

Although in theory the valves remain in the positions of the image, in reality and because the air has mass and inertia the valves open a little before and close a little after their respective times, hence for the same same Moto may be different camshafts, with different characteristics, which will change the "breathing" of the engine.
The camshaft consists of 1 axis in the Big Twin Evolution models, 2 axes on the Twincam models

and 4 axes in the Sportster models.

These axes rotate solidarity with the crankshaft, at half speed, and have an oval shape that pushes the rod that in turn opens and closes the valve.

But which is better?
When I have to explain which is the best camshaft for a given engine, I compare it with the gearbox, which everyone understands: it is not "better" for the circular engine in one march or another, the ideal march will depend on the Conditions of use and driving.
With the camshaft, the same thing happens, we have to choose the right taking into account several factors:
-The main use of the motorcycle (sports, city, loaded trip ...)
-Our driving type (relaxed, aggressive, "chopping" in traffic lights or dragging a trailer)
-The type of motor and the modifications we have made in it (if we have an engine with a lot of torque simply because it is very large we can sacrifice a little torque without hardly noticing it, if the engine rises to many rpm we can choose a suitable tree for work in this range ...)
One of the main features that the camshaft will decide is the point of maximum torque: in the same engine, if the maximum torque occurs at low RPM we will have strength, acceleration and ease of handling, if it occurs at high RPM we will have Power, speed and we will have to drive with more "joy."
In short, the camshaft does not increase or subtract power or torque, simply change the point where these variables reach their maximum value, changing the "personality" of our engine.

Types of camshaft
When choosing our camshaft it is highly recommended to go to a recognized professional, who will advise us in our selection based on the components of our engine and what we expect from their behavior.
Keep in mind that original camshafts are not complete From one with values ​​very similar to the original, it will provide changes in engine behavior, increasing the maximum torque and power.
A key point when choosing our ideal camshaft is to look at the closing degrees of the intake valve after the PMI (lower dead point), this data is provided by the manufacturer of the component:

-Meos from 30º will provide us with a large torque at low RPM, ideal for accelerations and heavy motorcycles.
-Of 30º to 50º It is generally a camshaft that enhances average regimes, perfect for light motorcycles and rapid driving.
-More than 50º are used in competition engines and prepared, which are constantly taken to high RPM and where the power prevails.

Hands to work
Once the camshaft is chosen, we only have to buy the appropriate joint kit and replace it, following the manufacturer's instructions (with very aggressive trees it is usually necessary to modify some components such as the valve springs or the rods of the pushers) and the workshop book of our model.
We are going to make the change in a 103CI softpoint, installing a crane camshaft that will provide a wider torque curve to the engine, which will obtain more thrust from very low revolutions to almost 5000 rpm, without losing power barely.

Comparing the camshafts of the previous photography we see the differences in the opening lobes of the valves, the highest manufacturing quality of Crane is also evident, with an improved finish.
We will lift the rockers to remove pressure on camshafts,

We will perform the substitution (you can consult This other technical article For more details on how to change the camshaft on a Twin Cam engine) and we will perform the assembly again following the manuals and respecting procedures and tightening pairs.

Adjustment and calibration
Once the installation has been carried out, we must modify the injection map to adapt to the new engine "breathing", since we will have increased the volumetric efficiency of the same in many parts of the map. This will be done by programming the switchboard,

After which we can already try the motorcycle on the road to observe the change of "character" of the engine.