STIHL MS 250 Smoke On Startup

Carburetor Rebuild Kit

The metering diaphragm and inlet needle valve are responsible for maintaining a fuel-tight seal when the engine is off. Over time, ethanol-blended fuels cause the diaphragm to stiffen, preventing the needle from seating and allowing fuel to 'puddle' in the crankcase. Replacing these components restores the volumetric efficiency of the fuel delivery system and prevents gravity/pressure-fed flooding during storage.

SKU: 1123 007 1061

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Complete Carburetor Assembly

Internal check valves or fuel circuits within the Zama C1Q carburetor can become obstructed or fail due to ultrasonic vibration or corrosion. If a rebuild kit fails to stop the flooding, the casting itself may have internal bypass issues that allow unmetered fuel into the intake tract.

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Air Filter

A heavily restricted air filter increases the vacuum signal at the venturi during the intake stroke. This pulls an excessive amount of fuel through the jets (choking the engine), leading to incomplete combustion and heavy smoke during the initial warm-up phase.

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