How to Adjust the Carburettor on a Stihl HS45 Hedge Trimmer

The Stihl HS45 Hedge Trimmer is a light and compact petrol powered trimmer, it's an efficient garden tool for trimming hedges and shrubs. If over time you find your hedge trimmer does not idle as normal, this may indicate that your carburettor needs adjusting.

The carburettor comes with a standard setting, this provides an optimum fuel-air mixture under most operating conditions.

We have put together some steps to adjusting your carburettor following the Stihl HS45 operators manual.

Preparations

First, shut off the engine.

You can now can check the air filter and clean or replace it if needed.

Check your cutting blades for damage and clean if it is necessary.

To access the speed screws you will first need to remove the limiter caps.

Standard Setting

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

Turn the high speed screw (H) counterclockwise as far as stop (no more than 3/4 turn). Turn the low speed screw (L) clockwise as far as stop, then turn it back 3/4 turn.

*Please note: Do not overturn the screw as this may damage the thread.

Adjusting Idle Speed

The Idle speed settings for the HS45 are set as followed (as advised by Stihl):

Carry out the standard setting.

Start and warm up the engine.

Adjust the idle speed with the idle speed screw (LA) so that the cutting blades do not run.

Cutting Blades run when Engine is Idling

Turn the idle speed screw (LA) counter clockwise 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 moving 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)

Idle setting is too lean

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

It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L).

Fine Tuning for Operation at High Altitude

A slight correction of the setting may be necessary if engine does not run satisfactorily:

Carry out the standard setting.

Warm up the engine.

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

Please Note: Incorrect adjustment of the carburettor could lead to damaging the engine, if you aren't sure, seek the help of a trained professional, always stick to the manufacturers guidelines.