How to Adjust the Carburettor on a Stihl HS45 Hedge Trimmer

The Stihl HS45 Hedge Trimmer is a lightweight, compact petrol-powered tool, ideal for trimming hedges and shrubs. If your hedge trimmer isn't idling properly, the carburettor may need adjustment.

The carburettor has a standard setting that optimises the fuel-air mixture for most operating conditions.

Here are the steps to adjust your carburettor, based on the Stihl HS45 operator's manual.

Preparations

First, turn off the engine.

Next, check the air filter and clean or replace it if necessary.

Inspect the cutting blades for damage and clean them if needed.

To access the speed screws, remove the limiter caps first.

Standard Setting

The standard settings for the HS45 are as follows (as advised by Stihl):

Turn the high-speed screw (H) counterclockwise until it stops (no more than 3/4 turn). Turn the low-speed screw (L) clockwise until it stops, then back it off 3/4 turn.

*Please note: Do not over-tighten the screw as this may damage the thread.

Adjusting Idle Speed

The idle speed settings for the HS45 are as follows (as advised by Stihl):

Perform the standard setting.

Start and warm up the engine.

Adjust the idle speed using the idle speed screw (LA) until the cutting blades stop moving.

Cutting Blades Run When Engine is Idling

Turn the idle speed screw (LA) counterclockwise until the cutting blades stop moving, then turn it another 1/2 to 1 turn in the same direction.

STIHL WARNING

If the cutting blades continue to move when the engine is idling, have your power tool checked and repaired by your servicing dealer.

Erratic Idling Behaviour, Poor Acceleration (Despite Correction to Setting of LA Screw)

If the idle setting is too lean:

Turn the low-speed screw (L) slowly counterclockwise until the engine runs and accelerates smoothly.

It is usually necessary to adjust the idle speed screw (LA) after any changes to the low-speed screw (L).

Fine Tuning for Operation at High Altitude

A slight adjustment may be needed if the engine does not run satisfactorily:

Perform the standard setting.

Warm up the engine.

Turn the high-speed screw (H) slightly clockwise (leaner) – no further than stop.

Please note: Incorrect adjustment of the carburettor could damage the engine. If unsure, seek help from a trained professional and always follow the manufacturer's guidelines.