STIHL BG 86 Pull Start

Spark Arrestor Screen

Carbonized oil deposits accumulate on the fine mesh screen over time, restricting exhaust gas flow. This creates significant pneumatic backpressure during the exhaust stroke of the engine cycle, making the pull-start cord feel physically harder to pull and preventing the engine from reaching the necessary RPM to achieve internal combustion.

SKU: 4241-141-9000

Carburetor Assembly

The internal needle valve and seat often fail or become contaminated, allowing fuel to leak into the combustion chamber while the engine is off. This results in a 'flooded' state or partial hydraulic lock; because liquid gasoline is incompressible, the piston encounters extreme mechanical resistance during the compression stroke, making the cord nearly impossible to pull until the fluid is cleared.

Ignition Module

If the module fails or the gap between the coil and flywheel is incorrect, it can cause the spark to fire too early in the compression stroke. This 'advanced timing' creates a premature explosion that drives the piston back down the cylinder prematurely, resulting in a violent 'kickback' that the user perceives as high resistance or a 'hard pull'.

SKU: 4241-400-1307