All about the camshaft on Harley-Davidson motorcycles

On numerous occasions we hear about this internal element of the engine, which is one of the great unknown in terms of its characteristics. The camshaft is not an element that is usually replaced when improving the engine of custom motorcycles, probably due to the lack of knowledge of the real changes in the behavior of the engine after its replacement.
We are going to 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 a high-performance one.

The function of the camshaft
This element is responsible for opening and closing the valves at the right time for the 4-stroke engine to occur: intake, compression, explosion and exhaust.

Although in theory the valves remain in the positions in the image, in reality and because the air has mass and inertia, the valves open a little earlier and close a little after their respective times, hence for the same motorcycle there may be different camshafts, with different characteristics, that will change the way the engine "breathes".
The camshaft consists of 1 shaft on Big Twin Evolution models, 2 shafts on TwinCam models

and 4 axles on Sportster models.

These shafts rotate in solidarity with the crankshaft, at half speed, and have an oval-shaped part that pushes the rod which in turn opens and closes the valve.

But which one 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 engine to circulate in one gear or another, the ideal gear will depend on the gear. conditions of use and driving.
The same thing happens with camshafts, we have to choose the right one taking into account several factors:
-The main use of the motorcycle (sports, city, loaded trip ...)
-Our type of driving (relaxed, aggressive, "biting" at traffic lights or towing a trailer)
-The type of engine and the modifications that we have made to it (if we have an engine with a lot of torque simply because it is too big we can sacrifice a little torque without hardly noticing it, if the engine rises to a lot of RPM we can choose a suitable shaft for work in this range ...)
One of the main characteristics that will decide the camshaft is the maximum torque point: in the same engine, if the maximum torque is produced at low RPM we will have strength, acceleration and ease of handling, if it is produced 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, it simply changes the point where these variables reach their maximum value, changing the "personality" of our engine.

Camshaft types
When choosing our camshaft, it is highly recommended to go to a recognized professional, who will advise us on our selection based on the components of our engine and what we expect from their behavior.
It should be noted that the original camshafts are not fully optimized to take advantage of maximum engine performance because they have to comply with strict emissions and noise regulations, which is why changing this component, even if it is one with values very similar to the original, will provide changes in engine behavior , increasing the maximum torque and power a little.
A key point when choosing our ideal camshaft is to look at the degrees of closure of the intake valve after the PMI (Lower DeadLock), this data is provided to us by the component manufacturer:

-Less than 30o will provide us with a high torque engine at low RPM, ideal for accelerations and heavy bikes.
-From 30o to 50o it is usually a camshaft that enhances the average regimes, perfect for light bikes and fast driving.
-More than 50o are used in racing and prepared engines, which are constantly carried at high RPM and where power prevails.

Let's get to work
Once we have chosen the camshaft we only have to buy the right gasket kit and perform the replacement of it, following the manufacturer's instructions (with very aggressive trees it is usually necessary to modify some components such as valve springs or pusher rods) and the workshop book of our model.
We're going to make the change to a 103ci Softail engine, installing a Crane camshaft that will provide a wider torque curve to the engine, resulting in more thrust from very low revs to nearly 5000 RPM, without losing power just.

Comparing the camshafts from the photo above we see the differences in the valve opening lobes, crane's highest manufacturing quality, with an improved finish, is also evident.
We'll lift the rockers to remove pressure on the camshafts,

we will perform the substitution (you can consult this other white paperfor more details on how to change the camshaft on a Twin Cam engine) and we will re-assemble by following the manuals to the letter and respecting tightening procedures and torques.

Adjustment and calibration
Once the installation is complete, we have to modify the injection map to suit the new "breathing" of the engine, since we will have increased the volumetric efficiency of the engine at many points on the map. We will do this by programming the switchboard,

after which we can already test the bike on the road to observe the change of "character" of the engine.