Abstract: An ignition system for an engine includes a position detector that generates a signal pulse while a segment of a member driven by the engine rotates past a given angular position. A first circuit produces a speed indicative voltage having a magnitude that is proportional to a duration of the signal pulse from the position detector. Upon termination of the signal pulse, a second circuit produces a second voltage the magnitude of which varies exponentially and an offset voltage is added to the second voltage at a node if the signal pulse is absent. A comparator has inputs coupled to the node and to the first circuit and produces an ignition signal when the voltage at the node and the speed indicative voltage are substantially equal.

Abstract: A system for controlling the air/fuel ratio input to a small engine measures the oxygen level in the engine's exhaust and compares it with a reference level. A stepper motor controls the air/fuel ratio and it is advanced one step each time a clock pulse is produced in a direction determined by the level of exhaust oxygen. A fault detector circuit stops the engine if the sensed oxygen level is outside a preset range for more than a preset time interval.

Abstract: An emission system especially for controlling evaporative emissions from the fuel system of a two cycle engine having a split exhaust wherein a combustor is provided to burn fuel vapor mixed with scavenging air exhausted from the engine and the combustor exhaust may be mixed with the engine blowdown gas for further treatment in a catalytic device or other treatment means. Additional control features are disclosed.