M-Tronic technology

Overview: M-Tronic technology 

• M-Tronic technology automatically controls fuel and air mix for optimal engine performance, adapting to changes in conditions like temperature and fuel quality without the need for manual adjustment.
• Uses electronics and a solenoid valve instead of manual carb adjustments.
• If any work is carried on the fuel supply system or the machine isn't running as expected, it's important to perform an M-Tronic reset.

What is M-Tronic?

M-Tronic is a STIHL engine management system that measures and regulates the fuel and air mix at all times. Much like the technology we see in modern day cars, its main purpose is to ensure that the engine always receives what it needs to perform at its very best.

What is the physical difference between an engine with M-Tronic and one without?

The main mechanical parts you would recognise in a normal working two-stroke engine are all still present and accounted for. There is still a fuel filter, air filter, carburettor, manifold, cylinder, piston, crankcase, crankshaft and flywheel, so mechanically it is the same.

However, if you were to look at the inner workings in more detail you are likely to see the following enhancements to a selection of parts, along with a couple of additions:

• Fan wheel – Two pole shoes are built in to the fan propeller and supply the control unit with electricity. This means the fan propeller not only provides cooling for the engine when you start up your chainsaw, it also generates its own energy supply to power M-Tronic.
• Ignition module – this now becomes a control unit, or the brains of the tool and features a microprocessor, electronic temperature recognition and ignition system.
• Carburettor H, L and LA screws are no longer present, these are replaced by a solenoid valve. The electronic solenoid valve takes just milliseconds to feed the correct amount of fuel into the engine as calculated by the control unit so you are getting the best performance fast.
• Combi-lever with stop button function – For a cold start, STIHL M-Tronic only needs one start position on the combi-lever. After starting, you can immediately power up to full speed.
• Addition of a wiring harness, or loom, which links up all the M-Tronic elements.
• Addition of a micro-switch- The micro-switch registers the position of the choke and, in conjunction with electronic temperature recognition, ensures easy starting throughout the day.

Is there any extra servicing required?

All the normal servicing and maintenance that is needed to keep your two-stroke tool in tip top condition still applies, so it is important that this is done regularly. If you do encounter any issues, it is always worth bearing in mind the part M-Tronic plays within the system too. For example, the solenoid valve, which is fitted to the carburettor, is directly involved in delivering the fuel/air mix, so it needs to be considered during the diagnosis stage.

Also, each M-Tronic machine can be re-calibrated at any time, so if there seems to be something not quite right during operation it is always worth performing an M-Tronic reset in the first instance. This can be easily done in-situ following the correct procedure within the specific tool owner’s manual, which can be found here. Re-calibration should only take a maximum of 90 seconds to do, although the newer tools are even quicker.

How to perform an M-Tronic reset

There are a couple of instances where you may need to reset your M-Tronic machine.

• Firstly, if you carry out any work on the fuel supply system, such as changing a solenoid valve, replacing or cleaning a carburettor or even just replacing an old fuel filter, you will need to do an M-Tronic reset.
• Secondly, if you find that the saw isn’t running as expected, for example, not revving to its full potential), it is always worth resetting your machine as this may offer a quick and simple resolution.

There are two methods to reset a STIHL machine with M-Tronic:

• Method 1 is for machines with M-Tronic 2.0 or lower
• Method 2 is for machines with M-Tronic 2.1 or higher

It’s easy to tell which version you have by looking at the CE label. Machines with M-Tronic 2.1 or higher are shown on the label as shown in this image. If it’s not shown on the CE label (M2.1 or M3.0) then it is likely you have an older version of M-Tronic.

Method 1 for M-Tronic re-set:

1. Remove the scabbard
2. Ensure the chain brake is engaged (on)
3. Put the machine in the ▲ Cold start position
4. Start the machine and run it in the ▲ Cold start position for at least 90 seconds
5. Do not touch the throttle or accelerate the saw during this time
6. After 90 seconds, switch off the machine
7. Your machine is now re-calibrated and ready for operation

Method 2 for M-Tronic re-set:

1. Remove the scabbard
2. Ensure the chain brake is engaged (on)
3. Put the machine in the ▲ Cold start position
4. Start the machine and run it in the ▲ Cold start position for at least 30 seconds but no more than 60 seconds (the period marked as A in the diagram below)
5. Do not touch the throttle or accelerate the saw during this time
6. Disengage/release the chain brake
7. Open/squeeze the throttle fully for at least 30 seconds (B in the diagram)
8. Engine speed varies noticeably during calibration
9. As soon as the engine speed drops noticeably (C), release the throttle back to the idle position
10. When the engine is back to idle speed, engage the chain brake and switch off
11. Your saw is calibrated and ready for operation

Always double check your Owners’ Manual to make sure you are following the right reset procedure.

Please note that when using a chainsaw, you should always wear the correct Personal Protective Equipment and take any necessary precautions.