When electronics and two-stroke engines are mentioned in the same sentence it can send shivers down the spines of even the most experienced users and mechanics. But we want to dispel the myth behind the technology and give you a clear and simple understanding of STIHL’s M-Tronic technology and how it works.
What is M-Tronic?
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.
M-Tronic constantly measures internal operating systems as well as external factors such as temperature, elevation and fuel quality. It also has a memory function, which means each time you start the saw (as long as conditions have not changed) the engine will be ready and primed for full performance.
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 re-calibrating the tool at 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.
For easier starting, it is always worth remembering that the saw only needs to be started in the triangle position on the main control lever, when the engine is cold. Once the machine has been started and used (and the engine is still warm), it should be started in the normal running position (I).
Have you got any questions about the M-Tronic engine management technology? What is your experience of tools with M-Tronic? We want your feedback so leave us a comment below.
A good blog, however you need to reiterate the start from cold and start from warm procedure. So many people get it wrong (albeit from not reading the manual). they then blame the saw. its good kit…. re iterate the above
Hi Jonathan, thanks for your feedback – we have updated the post to talk about the starting procedure when the saw is cold or warm! Hope that is useful!
Thanks for the detailed explanation of the M-Tronic system operation!
A failure of the solenoid valve can cause a “no-spark condition” due to “current loading” of the ignition module. Is this correct?
What is the expected DC resistance of the solenoid when measured with an ohm meter?
Hi Thomas, I’ve spoken to our Technical Team about this and we have never known of a “no spark” situation caused by the failure of a solenoid valve.
The only issues we have encountered with solenoid valves failing has been the valves leaking due to internal grit damage to the sealing polymer surfaces. Rather than testing a solenoid valve for resistance, we would recommend either a complete valve change or testing with our STIHL MDG-1 diagnostics unit, which can be done at STIHL Approved dealers. I hope that helps, thanks, STIHL GB
Hi I have learnt a lot from this thanks. I heard about a green fuel solenoid but someone said that it was discontinued. Can you tell me about it? I have a 2017 MS661cm and it often wont start when it is warm i am guessing it is the black solenoid can you tell me what i can do to fix it?
Thanks again.
Hi Josh, I’ve spoken to our Technical Team and they have said that, assuming the issue is not due to loss of spark, then it is possible it may be related to the carburettor and fuel solenoid. If so, they would suggest a pressure test of the carburettor and then a service of it including an internal clean, new diaphragms and a new solenoid. If in any doubt, please visit your nearest STIHL dealer for advice and servicing. With regards to the solenoid, some initial testing was carried out with a green solenoid, but a new white one was introduced that can be used as a replacement on some M-Tronic machines, including MS 661 C-M. I hope that helps, thanks, STIHL GB
Hi
I got a used MS 241 that won´t start. I fixed a broken line between the control unit and the solenoid, but still not starting. There comes too much gas into the engine, after a few times pulling the rope it drops out of the muffler.
It´s my first saw with M-Tronic, so I looked all over it and put out the solenoid for inspection also. Its the black one.
Can this solenoid can be taken out and in for a few times or has it to be replaced, once taken out?
Maybe the owner before me took it out as well, I don´t know.
Spark is comming, at least in normal position. I did not check in cold starting position, would this make a difference to the spark?
Hi Joe, I’m afraid it’s really hard for us to diagnose problems via the blog. We always recommend taking these products to a STIHL Approved dealer who is trained in how to deal with STIHL products. If you are based in Great Britain, you can also call our Customer Services team on 01276 417678 or email them at enquiries@stihl.co.uk. If you are based somewhere else in the world, you can find the contact details for your country here: https://www.stihl.com/default.aspx. Thanks, STIHL GB
I have a MS 102tc. I replaced a broken handle, and am absolutely sure all the linkages are correct. When I pull the trigger it does nothing. The choke revs it up.
Hi Jackie, thanks for your comment, but I’m afraid it’s really difficult to diagnose any issues in this way. We always suggest that you take it to a STIHL Approved Dealer to take a look as they have equipment to diagnose the issue. If they have any problems diagnosing the issue, they can also speak directly to our Technical team for assistance. You can find your nearest STIHL dealer here: https://shop.stihl.co.uk/pages/dealer-locator. Thanks very much, STIHL GB
Correction it’s an MS 201 tc
Most of your responses were hard to diagnose take it to approved Stihl dealer. Kinda of a cop out knowing that most people that own equipment work on their own stuff. New machines hold you hostage to the dealer and the hard/software!! Advancement shouldn’t be extortion !!!
Hi, thanks for your comment. Diagnosis over a blog or social media message without full information can often be counter productive. We often recommend to take it to a STIHL Approved dealer so it can be plugged in and/or diagnosed, so whilst we appreciate some people work on their own machinery, for the most efficient resolution we believe taking it to a STIHL Approved dealer is the best route. They’ll also be able to sell you a genuine and correct spare part for the specific model and also version of that tool as parts change over time. You are also welcome to email enquiries@stihl.co.uk if you need assistance on your tool, but STIHL GB are unable to sell spare parts directly and without seeing the machine, we can’t guarantee our advice would resolve the issue. Thanks, STIHL GB
I have an M Tronic 2 on my MS441c.
I cant get the saw to run more than a few seconds in the cold start position when trying to perform the 90 seconds calibration. Air filter, fuel filter and tank vent are all clean, could I be looking at replacing the solenoid?
Thanks, Chris
HI, thanks for your comment. We would recommend going to a STIHL Approved dealer who would be able to advise and also help with the correct solenoid if that is the worn part causing the difficulty running. Thanks, STIHL GB
It would be nice for Stihl to explain how these modules tick so owners can diagnose what’s wrong. I have a clearing saw with early Mtronic and the best I can get from it is 10s of rich running before it dies. Not everyone can afford a £800 diagnostics tester or the costs some workshops charge (if they can be bothered).. This leaves owners no option (like me) to change out the module, solenoid and tank filter.. I’m only changing the latter after finding debris inside the carb but the module with all its trickery is the unknown.. It won’t run long enough to carry out a reset either.. Cutting out after 10-20s regardless of speed.. Why??, How do I know what version of Mtronic I’m getting with a new module (4147 400 4720)?? I’m assuming (I can always scope it) that the solenoid is PWM controlled..
Good morning,
Thank you for your comment. Please can you contact enquiries@stihl.co.uk, someone from our Technical team will be in contact and will be more than happy to help you.
Thank you, STIHL GB.
Hi, does stihl m tronic on an ms462 have the ability to tell how many hours the saw has worked? Thankyou
Good morning, thank you for your question. Yes, the working time can be determined. It would require a STIHL Approved Dealer to do this, but they would be able to check the working time of any m-tronic saw. Thanks, STIHL GB.
Hi, I’m a huge mtronic fan and would never go back to a primitive manual carb now. It is a fantastic innovation.
What would be awesome is a software release note each time you upgrade mtronic. I’d love to understand the feature improvements across the different versions – improved heuristics and maybe any bug fixes?
Keep up the innovation!
Hi Edward, thank you for your comment and for suggesting new M-Tronic ideas. We will share this with our product team here at STIHL GB. Thank you, STIHL GB.
Stihl Ms261 idles fine but loses spark when revved ( inline spark tester confirms). Solenoid replaced with brand new, and still the same problem. Coil failure would be logical?
Cheers
Hi Josh, have you performed an M-Tronic reset, if not please use this blog as a guide: https://blog.stihl.co.uk/perform-m-tronic-reset/ If you are still having similar issues, please take your MS 261 to your local STIHL Approved Dealer for an inspection. Thanks, STIHL GB.
My MS 201 C-M, great saw, always starts well, but started misfiring and losing power when cutting – does not respond to reset.
Fitted a replacement white solenoid valve, but no improvement. Is this due to a faulty trigger unit, or something else in the wiring setup?
Hi Mike, thank you for your question. We’re sorry your MS 201 C-M is having some issues, our technical team have advised visiting your local STIHL Approved Dealer as it is difficult for our technical team to diagnose a problem without seeing the machine. You can find your local STIHL Approved Dealer here: https://shop.stihl.co.uk/pages/dealer-locator
Thanks, STIHL GB.