How to Tune Your Clutch for Better Performance with Olav Aaen's Clutch Tuning Handbook
If you are serious about racing or just want to get more performance from your variable ratio belt-transmission, you need to know how to tune your clutch. Clutch tuning is the process of adjusting the components of the clutch system to optimize the engagement and disengagement of the belt, which affects the acceleration, speed and efficiency of your vehicle.
One of the best resources for clutch tuning is Olav Aaen's Clutch Tuning Handbook, a revised edition of his classic guide that covers the latest in clutching technology. Olav Aaen is a renowned expert in clutch and carb tuning, who has been developing high-performance products and services for snowmobiles and all-terrain vehicles for over 40 years. His handbook provides detailed information on clutch theory, testing and flyweight machining, as well as specific chapters on Comet, Yamaha, Ski Doo, Polaris and Arctic Cat clutches.
In this article, we will give you an overview of some of the key concepts and tips from Olav Aaen's Clutch Tuning Handbook, and show you how you can apply them to your own clutch system. However, we highly recommend that you get a copy of the handbook yourself, as it contains much more in-depth and practical knowledge that will help you master the art of clutch tuning.
What is a Clutch System
A clutch system is a device that transfers power from the engine to the drivetrain by using a belt that runs between two pulleys. The pulleys are called the drive clutch (or primary clutch) and the driven clutch (or secondary clutch). The drive clutch is attached to the engine crankshaft, while the driven clutch is attached to the jackshaft or transmission shaft.
The pulleys have movable sheaves that can change their diameter depending on the position of the belt. As the engine speed increases, the drive clutch sheaves squeeze together, forcing the belt to ride higher on the pulley and increasing its effective diameter. This reduces the gear ratio and increases the speed of the driven clutch. Conversely, as the engine speed decreases, the drive clutch sheaves move apart, allowing the belt to ride lower on the pulley and decreasing its effective diameter. This increases the gear ratio and reduces the speed of the driven clutch.
The driven clutch works in a similar but opposite way. As the speed of the driven clutch increases, its sheaves move apart, forcing the belt to ride higher on the pulley and increasing its effective diameter. This reduces the gear ratio and increases the speed of the vehicle. Conversely, as the speed of the driven clutch decreases, its sheaves squeeze together, allowing the belt to ride lower on the pulley and decreasing its effective diameter. This increases the gear ratio and reduces the speed of the vehicle.
The combination of these two pulleys creates a variable ratio transmission that can adjust to different load conditions and terrain. The goal of clutch tuning is to find the optimal balance between engine power and vehicle speed for maximum performance.
What are Clutch Components
The main components of a clutch system are:
The belt: The belt is a rubber or composite material that connects
the drive and driven clutches. It must be strong enough to withstand
the tension and friction generated by the clutches, but flexible enough
to conform to their changing diameters. The belt should be inspected
regularly for wear and tear, and replaced if necessary.
The flyweights: The flyweights are metal weights that are attached
to arms inside the drive clutch. They are responsible for controlling
the movement of the drive clutch sheaves by applying centrifugal force
as they spin with the engine. The shape, size and position of
the flyweights affect how quickly and how much they move
The spring: The spring is a coil spring that is located inside
the drive clutch. It opposes
the centrifugal force of
the flyweights by pushing
the sheaves apart. The stiffness,
length and preload of
the spring affect how strongly
and when it pushes
The helix: The helix is a metal ramp that is attached
to one of
the sheaves of
the driven clutch. It controls
the movement of
the driven clutch sheaves by applying torque as it rotates with