MS261CM M-Tronic Issues and Many GFY’s

[hseII]

On the coil

I suppose the Stihlership MGD2 or whatever it’s called can read it?

That sounds Kind of like a little black box on an airplane except for saws.


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[huskihl]

Thanks Kevin.

Another stupid question then, could coil air gap then affect coil temp?
Hotter spark, more induced heat?

Im just thinking on my mower engine days, we ran billet flywheels with rare earth magnets and gaps were .040-.060" and changing it was enough to alter cylinder head temps with no other changes.

Not certain. I've read that it can advance the timing a slight amount the closer the coil is to the fw

 

[DND 9000]

I suppose the Stihlership MGD2 or whatever it’s called can read it?

Yes when the machine is connected with the diagnostic tool during the test. But only current temperature during data read out. No min or max temp like on the Husqvarna AutoTune System.

 

[ABarrick]

Subbing to see where this goes.

My 261c has been doing this since I bought it. 11/17 build date. Seemed way too lean since day one. It WILL NOT four stroke at WOT. It will hit a rev limiter eventually but it sounds ignition limited, not fuel. It’s muffler modded (pretty open) and timing advanced. Those things actually seemed to help the problem, not make it worse. I run 16”3/8 on it. It runs like a freakin raped ape until you bury the bar for a dozen cuts in 12-16” diameter oak and then you can feel it slowing down. Not unusable, but it’s a noticeable drop in power. Feels like it’s running out of fuel. Let it cool off and it’s ready to rip again. It’s mostly a limbing saw so it hasn’t been a big issue but I notice it. Dealer said just run it, it’s got a 2 yr warranty lol

I’ve always assumed it was getting too hot, but it hasn’t died yet. I run VP sef with Ultra at 40:1

Interesting stuff for sure.

 

[whitesnake]

I would just try some canned 40:1 fuel...could just pick up a quart even.

 

[Bilge Rat]

Giving up control to a bunch of electrons is just wrong.
Small motors, small carb passages can be finicky. Oil thickness could be an issue.
Could it cause a slightly lean condition, run hotter and the MT not being able to fully compensate?

Tis a puzzle

 

[shadco]

That’s strange for me.

Both my 362 & this 261 didn’t seem to mind?


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My 261,241, and 572 don’t mind 32:1 Maxima K2 at all. Efree 89.

.

 

[Greg Newman]

I normally run non E 87 with Yamalube 2R @ 40:1

I run exact same in my m-tron saw never had a problem.

 

[Wonkydonkey]

Subbing to see where this goes.

My 261c has been doing this since I bought it. 11/17 build date. Seemed way too lean since day one. It WILL NOT four stroke at WOT. It will hit a rev limiter eventually but it sounds ignition limited, not fuel. It’s muffler modded (pretty open) and timing advanced. Those things actually seemed to help the problem, not make it worse. I run 16”3/8 on it. It runs like a freakin raped ape until you bury the bar for a dozen cuts in 12-16” diameter oak and then you can feel it slowing down. Not unusable, but it’s a noticeable drop in power. Feels like it’s running out of fuel. Let it cool off and it’s ready to rip again. It’s mostly a limbing saw so it hasn’t been a big issue but I notice it. Dealer said just run it, it’s got a 2 yr warranty lol

I’ve always assumed it was getting too hot, but it hasn’t died yet. I run VP sef with Ultra at 40:1

Interesting stuff for sure.

I thought your reply was interesting,....in the way when you tune a normal saws carb, forsure you have to retune it when it’s hot. As it leans out a bit if it’s not.

So mtron saws, It seems to be run ok till hot/very hot, then goes funny.

Also we know. Advancing the timing can make a saw run hotter.
is this the real answer to this funny runnning problem...

 

[huskihl]

I thought your reply was interesting,....in the way when you tune a normal saws carb, forsure you have to retune it when it’s hot. As it leans out a bit if it’s not.

So mtron saws, It seems to be run ok till hot/very hot, then goes funny.

Also we know. Advancing the timing can make a saw run hotter.
is this the real answer to this funny runnning problem...

I don't see as many saws as some on here. Maybe 40-50 per year. So this is based on my own experience and not a general statement about electronic carbs. Of the 10 or so electronic models I've done, this is the only 261 v2, and it's the only one that's done this. I don't think it's across the whole 261 line up, I think it's one here and there.

I'm currently waiting on a softer pump diaphragm. The one in it is crispy plastic and maybe a softer one will flow more fuel

 

[drf256]

Tossed a 20 on it to start. Figured maybe the 25 was just too much. Same fuel, 32:1 motul, and same shít.

 

[drf256]

Changed nothing except mix to VP Racing 92 octane and Saber at 42:1. Saw felt like it would do same, but it compensated.

Sorry for long video, I wanted it to happen again, but it didn’t.

Saw still shuddered after coming out of the cut.

 

[drf256]

Took more out of the squish. Got it to 20.

Fixed it all.

 

[drf256]

Ran a muff modded and equally advanced stock cylinder 261 and it ran fine on 32:1 Motul.

 

[drf256]

So it seems if the MT 261 gets hot, the MT wants to richen the saw but can’t if the mix is too thick.

The compression and TA add heat that can’t be compensated for, to a degree.

 

[ABarrick]

I thought your reply was interesting,....in the way when you tune a normal saws carb, forsure you have to retune it when it’s hot. As it leans out a bit if it’s not.

So mtron saws, It seems to be run ok till hot/very hot, then goes funny.

Also we know. Advancing the timing can make a saw run hotter.
is this the real answer to this funny runnning problem...

Mine doesn’t behave as badly as docs in the video does, but it’s enough you can notice it. Advancing the timing didn’t change anything on mine. If it had a regular carb I’d turn the H out an 1/8 and call it a day.

Glad he got it figured out. Unfortunately none of what helped his is really relevant for me as mines not ported.

 

[tree monkey]

talking with mike today , he said his coil does not advance. pretty sure this vid is of a gen 1 261. if the coil does not advance there could be more wrong with it. like not feeding enough fuel. might be worth looking into further.

 

[huskihl]

talking with mike today , he said his coil does not advance. pretty sure this vid is of a gen 1 261. if the coil does not advance there could be more wrong with it. like not feeding enough fuel. might be worth looking into further.

Yours didn't advance, did it? Looked like when you hit 10k the light went out

 

[tree monkey]

it advances off idle

 

[huskihl]

it advances off idle

This one did what yours does. 20° btdc from 4k through 10k with a slight retard at idle. Maybe 5°