Crankshafts & Connecting Rods

Viva la Revolution with 24MX Crankshafts and Camshafts

The crankshaft and camshaft sit at opposite ends of the engine. The crank sits at the very bottom of the engine in the crankcase. Meanwhile, the camshaft sits at the top of the engine in the cylinder head.

While their roles are different, they must work in complete synchronicity for the engine to operate correctly. The two often connect via a toothed belt or, more commonly, a cam chain, especially in motocross engines.

Camshaft – The length of the camshaft is proportional to the number of cylinders in the engine. Most motocross engines have one cylinder with a single overhead cam, so the camshaft is short in length.

The pear - shaped lobes on the cam are there to open and close the inlet and outlet valves. For high-performance engines, the lobe profile is larger to allow more air and fuel in and exhaust gasses out.

Crankshaft - While the camshaft has a more high-profile job with the cylinder head designed around it, the crankshaft is buried deep in the engine's bowels. Make no mistake, though. The crankshaft is an engine’s backbone.

A dirt bike crankshaft is a heavyweight piece of kit. Either made from forged or billet steel, it converts the vertical movement of the piston into horizontal rotation, which powers the back wheel.

While it’s possible to purchase each part of the crank individually, an aftermarket crankshaft kit offers many advantages. The kit generally includes the con rod and bearings, and both components will arrive pre-installed on the crankshaft to ensure excellent fit and balance.

Reasons for Buying a New Motorbike Crankshaft

Wear - Camshafts may have a tough job but the crankshaft spins twice as fast. Considering the weight and speed of the crank and the load imposed on its bearings, you can appreciate why wear occurs.

When the bearing or crank journal wears, you will experience excessive vibration throughout the engine. Left unchecked, or if the crankshaft becomes starved of oil, it can result in catastrophic engine damage.

Performance – You don't need to wait for components to wear out; if you're considering a performance upgrade, the best place to start is the bottom end. The biggest problem for a motorbike crankshaft is its reciprocating weight. Aftermarket crankshafts are often lighter than factory originals so that they can rev higher and smoother.