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Why Reed Induction?

Reed induction is a staple of two stroke performance engineering because it is one of the simplest, most reliable ways to make big power.


  • Faster throttle response
  • More available horsepower across a larger RPM range
  • Better cylinder filling at high RPM for peak horsepower
  • Better control of the fuel/air ratio

If that wasn't enough, MB Products' crankcases and reed cages are designed to maximize the performance of our engines with more crankcase compression, and smoother airflow.

Popularized by Yamaha in the 70s, reed valves are now being used extensively in marine outboards, Grand Prix racers and hobby engines. So what gives? What’s the secret behind the magic?
Let’s simplify things.

An engine is an air pump. Air goes in. Air goes out. We add fuel for combustion to drive this process and oil to lubricate the system.

Four-stroke engines control the flow of air with valves. When the intake valve opens, air and fuel enter the cylinder and the valve shuts behind them like a door. The mixture is compressed and ignited. The heat and pressure generated forces the piston(s) down to rotate the crankshaft. (We use this rotation to drive gears, pulleys, props, and drive shafts to get us moving.) At the end of the four-stroke cycle, the exhaust valve opens to release the waste (used air and fuel) and closes shortly after so the spent gasses don’t re-enter the cylinder.

Since most two-stroke engines don’t have valves, opening and closing of the intake and exhaust is controlled by the position of the piston in the cylinder. When the piston is blocking a port, the port is closed. When it isn’t, the port is open. Engines that control this opening and closing using only the piston are called piston-port engines. So what’s their problem? At low RPM, piston-port engines lose some of the fuel-air-oil (FAO) mixture through the intake port as back-flow. As the piston drops, closing the intake port, crankcase pressure increases and pushes the intake charge through the transfer ports toward the top of the piston. That same pressure also forces some of the FAO mixture backwards through the intake. That lost fuel and air could have been used to generate horsepower. This happens over and over again, until the engine reaches a high-enough speed for the vacuum to flow in one direction with minimal reversion.

Reed valves only let air flow one way, so at low RPM we won’t experience reversion. That also means we won’t lose power. This lends to more available horsepower across a larger RPM range and a broader torque curve, which we call the “powerband.”