Mtronic - which model, which reset procedure?

Jackjcc

Active Member
It looks well used, but I wouldn’t replace it yet. A compression test would be the next step, anything over 130psi should run fine, but 150 is the ideal number.


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samsquatch

Active Member
pretty much since I got it. I've tried to run it several times since I bought it and just get frustrated with how it runs.

It won't start when it's hot, and will often die at idle.
 

Birdyman88

Well-Known Member
Yeah, it sounded like that was the deal. Here's what I would do, keep in mind that I'm anal as hell when it comes to troubleshooting stuff, but I've learned my lessons in the past about overlooking simple stuff and relying on my dealer's word:

NORMAL STUFF
1) clean air filter
b) check fuel filter for flow (use air)
3) clean spark arrestor
4) fuel - ethanol or not? - are you seeing issues on other saws/equipment
5) clean clutch assembly, then finish clean with some carb or brake cleaner, don't overcook it
6) chain is not too tight - I hate to even say that
7) spark plug is correct model, clean, gapped correctly, torqued properly
8) spark plug is not cracked or showing signs of damage
9) Spark plug boot fits snugly/clicks onto the plug
10) DONE - piston is not scored, compression check
11) carburetor bolts/nuts are tight
12) muffler bolts/nuts are tight
13) make sure all the fuel lines are clear, connected, and the connections are snug
14) make sure the impulse line is clear, connected, and connections are snug
15) ensure tank vent is clear
16) shoot the carburetor with carb cleaner - small bursts as it will be like straight-gassing
17) compression release valve is torqued and there aren't any signs of blow-by
18) general leak test - while idling short bursts of brake or carb cleaner all around engine and carb and look for rpm changes - just know that when you get near the air intake area it will change rpm and that's normal
19) verify the coil connections are clean and tight
20) verify spark the best you can - the really good tester isn't cheap
21) remove air filter and saturate the carb inside and out with some PB Blaster and let it sit for an hour - try to get it into the jets - flush with some carb cleaner and let it evaporate before you crank it up
22) check for ethanol damage to carb - PB Blaster helps, but may need more thorough cleaning, and replacement of fuel pump and metering diaphragms

NOT SO NORMAL STUFF BUT THE LAST OWNER COULD HAVE MESSED WITH
1) all engine parts are OEM - this may take some time but verify/inspect
2) cylinder bolts are torqued to spec - this would likely be revealed in leak test
3) VERIFY THE COIL AND SOLENOID BELONG TO THE SAME MTRONIC VERSION!!!! - I would not bet my life that in a previous life one of the two wasn't replaced with a non-matching part and your dealer may not have verified
4) DOUBLE CHECK THAT THE LINKAGE IS CORRECT AND/OR FITTING PROPERLY
5) verify your dealer actually replaced that solenoid and it is V2
6) verify the coil is mounted correctly and has the proper gap to the flywheel - if someone replaced the coil in the past, this could be a biggie
7) verify the flywheel magnet isn't damaged
8) check the flywheel key for modification and verify that the timing hasn't been altered
9) check the muffler and verify that it hasn't been [incorrectly] modded
10) IF ALL ELSE FAILS - replace the coil with another V2 coil or whatever matches the solenoid the dealer put on - or upgrade coil and solenoid to V3.
11) anything else?
 
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samsquatch

Active Member
Is there anything special with removing these mtronic carbs and/or getting good access to the fuel lines to run some air thru them?
 

samsquatch

Active Member
To answer my own thread:
8D188031-43F5-4F97-B4E3-C743D75BAE90.jpeg

Including the text for future search-ability.
5.4.2 Determining the STIHL M-Tronic™ version
Control unit software version can only be
determined for chain saws and only from
STIHL M-Tronic™ version 2.1.
The STIHL M-Tronic™ version is indicated on the
emissions label after the material no., e.g.:
If there is no such indication on the emissions label,
the STIHL M-Tronic™ version is lower than 2.1.
5.4.3 Resetting control unit to factory default
settings
S Remove saw chain and guide bar or cutting
attachment.
S For chain saws: Remove the chain sprocket
cover.
S Set control lever to the }position.
S Start engine, without depressing the throttle
trigger.
S Allow engine to run for at least 90 seconds in
position }.
S Switch off engine.
The control unit has been reset to the factory default
setting. The engine electronic system has been
adapted to the new solenoid valve.
 

Jackjcc

Active Member
No they have connectors to let you take the wires off, just be careful and take a pic before.

I would caution with spraying carb cleaner into the carb when it’s on the saw. Carb cleaner will wash out a lot of stuff into the crank and then also wash off the layer of oil on the parts.


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Birdyman88

Well-Known Member
@samsquatch I just called Stihl and wanted to clarify a few things with them. Here's what they said.

1) The 90 second reset procedure for V2 puts everything back at factory settings, but the saw is not calibrated to environmental conditions at this point. You still have to do the 5 uniform cuts before saw optimizes itself. The V3 version uses the 30/30 reset, but you still have to do the 5 uniform cuts to optimize saw to conditions.

2) The black solenoid is what came on the V2, the white solenoid came on V3. On the 362 you can pair a white V3 solenoid with a V2 coil and it will work fine. You cannot pair a V3 coil with a black V2 solenoid - you will have run issues. On the 661, you can pair a white V3 solenoid with a V2 coil and it will run fine, but Stihl is requiring that the coil be upgraded to V3 to meet EPA. The problem with the V2 solenoid was the use a plastic disc along with a metal disc - the plastic disc was wearing out prematurely and causing a rich condition at low rpms. V3 solenoid uses two metal discs.
 

samsquatch

Active Member
Well, it was a long afternoon. I disassembled the jug, inspected the piston and it is not scored, at least appreciably. Also cleared out the fuel line, fuel filter, tank vent, and carb, carb diaphragm. Inspected the intake boots, removed and cleaned the flywheel and the coil pickup. Reassembled and didn't have any parts leftover. ;) Anyway, I did a good job, everything is clean, linkage is all there and correct, nuts and bolts all tight. I thought for sure this thing was going to run better.

I drove to the farm to test it out in some wood. Did the 90 second mtronic reset and started my 5 uniform cuts. But it ran the same as it did before the breakdown. still doesn't have the acceleration snap that my other 362CM has, and cut very poorly - like it had no balls. I'm pretty sure my 193T can outcut it at this point.

I'm leaning now toward the mtronic coil itself. Or maybe crank seals - but how can they be tested? There's no impulse line on this saw... at least that I seen.
Cheers
 
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Jackjcc

Active Member
Since it is a strato, fuel charge and air paths are separate, it’s most likely integrated into the boot on the bottom end.


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samsquatch

Active Member
Ah, going thru the Stihl technical manual now, it appears that the diaphragm in my carb was a bit too "stiff". My experience with other diaphragms (in older small engines, tecumseh, briggs) is they are very pliable. The one in this saw was very very thin and "snappy", not rubber-like at all. Maybe I'll tear apart my other 362 to compare diaphragms.
Cheers
 

Birdyman88

Well-Known Member
You can check the crank seals using carb cleaner. Just spray a little down around the crank while idling and look for rpm change. Go short and light at first in case they are bad.

Just keep knocking out all the other checks. I have had some luck with PB Blaster on a couple of carbs, so give it a shot. That doesn't take much time.
 

Birdyman88

Well-Known Member
@samsquatch What is the part number on your coil? it will be a 470x number. If you are V2 saw with black solenoid, it should be a 4701A. If it says 4702, 4703, or 4704, then that is a V3 coil and you will need the white solenoid. Don't mean to beat a dead horse, but you got to rule it out seeing someone else had saw ... and coil could still be defective or another problem altogether.
 

samsquatch

Active Member
You can check the crank seals using carb cleaner. Just spray a little down around the crank while idling and look for rpm change. Go short and light at first in case they are bad.
How can you spray the crank seals while the engine is running? I mean, you need the flywheel on to start the engine.
 

Jackjcc

Active Member
How can you spray the crank seals while the engine is running? I mean, you need the flywheel on to start the engine.
Look up vacuum testing a chainsaw. You can do it with as little as bike tire tubing, hose, hand pump and shrader valve.

If you start the saw and flip it on all sides and the idle speed increases, that’s the best indication of an air leak. That’s the point where I would be checking the seals. I feel you have a fuel delivery issue.


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