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S&S Cycle Motorcycle Camshaft

Motorcycle engines are air pumps, and the better they can breathe, the more power you can get out of them. The fuel/air mixture enters the cylinders through one set of valves and leaves through another. The camshaft holds the cams that control the valves, determining how far they open and for how long. S&S Cycle makes aftermarket camshafts for a number of motorcycles, particularly Harley Davidson.

How Camshafts Work

Like so many other engine parts, camshafts drive from the crank. As the engine turns over, the camshaft rotates, opening and closing the proper valves in time with each intake and exhaust stroke. Cams do most of the work by themselves, or by lobes, which have eccentric shapes to force the valves to move a predetermined distance at the proper time. The variable diameter of the lobe pushes the valve open at one part of the revolution, and then lets the spring hold it closed the rest of the time.

Overhead vs. Pushrod

Many modern motorcycles feature overhead camshafts, while others mount the camshaft in the block and rely on pushrods and rocker arms to actuate the valves. Each approach has its advantages and disadvantages. Overhead camshafts perform better at high RPM, but they are more complex. Pushrods are easier to maintain and adjust, but offer lower high RPM performance. One reason pushrods are still popular with manufacturers like Harley Davidson is that they reduce the height of the engine, which makes design easier.

Camshaft Kits

It's rarely possible to install motorcycle camshafts on their own. Like most other motorcycle parts, they form part of a system. Most camshaft kits include new drives for the camshafts as well as the appropriate gaskets and seals. Never reuse existing gaskets, as they will not hold a seal. A gear drive is a worthwhile upgrade because it gives you tighter timings than a chain drive.

Heads

Whether you have an overhead cam or pushrod engine, S&S Cycle motorcycle cylinder heads and valve covers are a great complement to S&S Cycle camshafts. Each engine block requires heads to match, and you have to be careful to make sure your choice matches the valve train in your bike.

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