V.3 M-Tronic Coils for the MS661 C / New Calibration Procedure

[singinwoodwackr]

How do you like the 500i? On paper it has the same power as the 661 and weighs less.

They are 2 completely different saws.

 

[PogoInTheWoods]

So, just to be clear, the 1144 400 4704B coil uses the calibration procedure in the video? I don't want to mess this up. I messaged the seller and he claims a tool is needed to program the new coil.

The 4704B is a Gen3 module and requires the procedure described in post #1. No 'tool' required and is probably the rather useless MDG1 diagnostic system Stihl introduced to support the M-tronic units as erroneously understood by your seller as well as most Stihl dealers. Your kit should have included a cheat sheet like the one also included in post #1 describing what the admittedly poor video attempts to show -- minus the second WOT sequence as explained.

I probably had around 1000 hours on each of them before I got tired of throwing money at them and set them aside. Depending on the job I cut as low as 2500' up to around 6500'. I bought both of them in 2018. No ethanol, 89 octane and Stihl synthetic at 50:1. My dealer is sick of them.

Your dealer probably had very little useful support from Stihl and probably still doesn't. All they did was throw solenoids and carbs at the 661's back then and had no clue what was going on with the ECMs. None. Stihl didn't either. Most dealers still don't. Any M-tronic 661 with a good crank can be revived into a solid Gen3 performer capable of many hours of hard core use.

I followed the old recalibrate procedure on both and both are stihl running perfectly after nearly a year of hard use at a firewood yard. Go figure…

The probability is very high that they have later Gen1.1 ECMs for that procedure to be effective. There are still plenty of Gen1s out there running. There was no 'Gen2' in the States.

BTW, the operator in the video actually IS a Stihl dealer and had no idea about the new ECMs or the procedure until the day that video was shot when I brought the saw in after rebuilding it. Go figure...

 

[WI_Hedgehog]

@Dave4610 : The 500i is a screamer, but the power seems high in the rev band so to me they sound like banshee. LOL

Jack brought a ported one to the WI_GTG this past weekend and while powerful it was obnoxiously loud. (not kidding)

Porting can add an incredible amount of power (at the expense of noise), but saw longevity which is normally 3,000-3,500 hours decreases due to the added stress, a strong port job saw might last 1,000 hours (which is a lot of hours). People don't want to talk about that, but in the engine world builders know a block is good for a certain amount of power, how fast you burn through that is up to you. Saws are designed and built for a specific load level, if the load is increased so is the wear, though it's not linear (it's exponential) so more load results in "significantly" more wear, though there are a lot of factors that play in. For instance, people are pretty open about not porting a milling saw due to the extended loads and heat buildup, so usage affects saw lifespan, moreso when ported. Conversely a gentle "woods port" which removes extreme EPA restrictions and keeps things "reasonable" won't affect saw life "that much" and is offset by an increase in production (and take-home pay). On the other end of the spectrum is a race-saw (hot saw) that has a very short lifespan though insane amount of power. Just be reasonable with your expectations.

If you're referring to Brad Snelling ( @blsnelling ), he's an awesome guy and phenomenal builder, though no longer building saws as far as I know.

 

[PogoInTheWoods]

Not sure what that has to do with the subject of the thread, but I will add one more note that sorta does and could be considered a sleeper aspect to the early 661 M-tronic problems; poor air filtration.

Combine that with already wandering (mostly lean) ECM adjustments at extended high RPMs and bad just went to worse without the filtration being an obvious consideration toward why the ECMs were wandering in the first place. It's also just plain bad filtration on a conventional carb saw.

There are threads about why Max-Flo is the way to go for most high performance Stihls, but I'll simply say I agree and leave it there.

There are also lots of very comprehensive M-Tronic threads elsewhere (OPIE) if one has the time or interest to learn more about the subject.

 

[Dave4610]

I believe he stopped building saws years ago

Sounds like my typical luck...

 

[Dave4610]

@Dave4610 : The 500i is a screamer, but the power seems high in the rev band so to me they sound like banshee. LOL

Jack brought a ported one to the WI_GTG this past weekend and while powerful it was obnoxiously loud. (not kidding)

Porting can add an incredible amount of power (at the expense of noise), but saw longevity which is normally 3,000-3,500 hours decreases due to the added stress, a strong port job saw might last 1,000 hours (which is a lot of hours). People don't want to talk about that, but in the engine world builders know a block is good for a certain amount of power, how fast you burn through that is up to you. Saws are designed and built for a specific load level, if the load is increased so is the wear, though it's not linear (it's exponential) so more load results in "significantly" more wear, though there are a lot of factors that play in. For instance, people are pretty open about not porting a milling saw due to the extended loads and heat buildup, so usage affects saw lifespan, moreso when ported. Conversely a gentle "woods port" which removes extreme EPA restrictions and keeps things "reasonable" won't affect saw life "that much" and is offset by an increase in production (and take-home pay). On the other end of the spectrum is a race-saw (hot saw) that has a very short lifespan though insane amount of power. Just be reasonable with your expectations.

If you're referring to Brad Snelling ( @blsnelling ), he's an awesome guy and phenomenal builder, though no longer building saws as far as I know.

Yes, I was referring to that Brad. I bought a ported 201t from him. I love that saw! I was hoping he still built saws

 

[Dave4610]

Not sure what that has to do with the subject of the thread, but I will add one more note that sorta does and could be considered a sleeper aspect to the early 661 M-tronic problems; poor air filtration.

Combine that with already wandering (mostly lean) ECM adjustments at extended high RPMs and bad just went to worse without the filtration being an obvious consideration toward why the ECMs were wandering in the first place. It's also just plain bad filtration on a conventional carb saw.

There are threads about why Max-Flo is the way to go for most high performance Stihls, but I'll simply say I agree and leave it there.

There are also lots of very comprehensive M-Tronic threads elsewhere (OPIE) if one has the time or interest to learn more about the subject.

Is "OPIE" supposed to be OPE or what is OPIE?

 

[rogue60]

Not sure what that has to do with the subject of the thread, but I will add one more note that sorta does and could be considered a sleeper aspect to the early 661 M-tronic problems; poor air filtration.

Combine that with already wandering (mostly lean) ECM adjustments at extended high RPMs and bad just went to worse without the filtration being an obvious consideration toward why the ECMs were wandering in the first place. It's also just plain bad filtration on a conventional carb saw.

There are threads about why Max-Flo is the way to go for most high performance Stihls, but I'll simply say I agree and leave it there.

There are also lots of very comprehensive M-Tronic threads elsewhere (OPIE) if one has the time or interest to learn more about the subject.

I'm not sure what crap oil you guy's run but I've never personally seen any damage or premature wear caused by fines/sawdust getting past the filter. and that's even with timber with very high silica content.

This is an early first coil very high hr ms661. (I wiped any oil off the piston for a better look at any wear)
And here's you guys freaking out about one or two fines getting past ya filter lol

 

[Dave4610]

The 4704B is a Gen3 module and requires the procedure described in post #1. No 'tool' required and is probably the rather useless MDG1 diagnostic system Stihl introduced to support the M-tronic units as erroneously understood by your seller as well as most Stihl dealers. Your kit should have included a cheat sheet like the one also included in post #1 describing what the admittedly poor video attempts to show -- minus the second WOT sequence as explained.


Your dealer probably had very little useful support from Stihl and probably still doesn't. All they did was throw solenoids and carbs at the 661's back then and had no clue what was going on with the ECMs. None. Stihl didn't either. Most dealers still don't. Any M-tronic 661 with a good crank can be revived into a solid Gen3 performer capable of many hours of hard core use.


The probability is very high that they have later Gen1.1 ECMs for that procedure to be effective. There are still plenty of Gen1s out there running. There was no 'Gen2' in the States.

BTW, the operator in the video actually IS a Stihl dealer and had no idea about the new ECMs or the procedure until the day that video was shot when I brought the saw in after rebuilding it. Go figure...

Thank you for the reply and info! I don't recall seeing a cheat sheet in the box. I'll look again, but I don't think there is one.

 

[singinwoodwackr]

so, got an early 661 back in today that I had swapped to a white solenoid last year. It ran fine until today...pretty hard use in a local firewood lot. It will not idle normally, rather, it goes into fast idle and stays there. You can rev it up but it refuses to drop to idle rpm’s. It will cut ok at wot.
I tried the 90sec restart procedure 3 times, no joy.
I do have a couple extra solenoids so will try that. But, anyone else have this fast idle issue?

 

[bwalker]

so, got an early 661 back in today that I had swapped to a white solenoid last year. It ran fine until today...pretty hard use in a local firewood lot. It will not idle normally, rather, it goes into fast idle and stays there. You can rev it up but it refuses to drop to idle rpm’s. It will cut ok at wot.
I tried the 90sec restart procedure 3 times, no joy.
I do have a couple extra solenoids so will try that. But, anyone else have this fast idle issue?

Bad air leak maybe?

 

[singinwoodwackr]

Bad air leak maybe?

Maybe, vac and pressure testing upcoming but it is a steady fast idle, no surging.

I only have spare green solenoids; will they work or should I get another white?

No scoring front or back of cyl but a lot of blow-by...this don't look right

Stock saw with muffler mod only. 50:1 stihl mix

Plug looks fouled but after reset, not surprised.

4702A coil

Comp: just under 160 which makes sense with that much blow-by

...

 

[bwalker]

Maybe, vac and pressure testing upcoming but it is a steady fast idle, no surging.

I only have spare green solenoids; will they work or should I get another white?

No scoring front or back of cyl but a lot of blow-by...this don't look right

Stock saw with muffler mod only. 50:1 stihl mix

Plug looks fouled but after reset, not surprised.

4702A coil

Comp: just under 160 which makes sense with that much blow-by
View attachment 1118718
View attachment 1118717...View attachment 1118720View attachment 1118721

Thats not blow by. That's from running Stihl Ultra I bet? Does the piston still have machine grooves? If it does its not blow by.
I have had engines where they idled fine, but where. Ost certainly leaking air. So a vac and pressure test is a good step to take.
I can't speak to 661 solenoids.

 

[chipper1]

Maybe, vac and pressure testing upcoming but it is a steady fast idle, no surging.

I only have spare green solenoids; will they work or should I get another white?

No scoring front or back of cyl but a lot of blow-by...this don't look right

Stock saw with muffler mod only. 50:1 stihl mix

Plug looks fouled but after reset, not surprised.

4702A coil

Comp: just under 160 which makes sense with that much blow-by
View attachment 1118718
View attachment 1118717...View attachment 1118720View attachment 1118721

Dang stihls .
All the 661's I've had ran great, I'd buy another if I needed a 90cc saw. The again, I'd like to try a 592xp, never ran one.

 

[singinwoodwackr]

Trying to check for air leaks, pulled clutch to inspect seal on that side…the clutch/drum was near welded together, sigh. Owner has been using Costco cooking oil as bar oil, sigh…
kinda esplanes the fast idle

 

[Long Bar 60]

Trying to check for air leaks, pulled clutch to inspect seal on that side…the clutch/drum was near welded together, sigh. Owner has been using Costco cooking oil as bar oil, sigh…
kinda esplanes the fast idle

Seriously? Wow!

 

[singinwoodwackr]

Seriously? Wow!

Ever leave a pan with cooking oil on the stove at low heat? Yup, same results…
and, add nice, fine pine and fir dust to the mix…

After several minutes in the sonic tank with purple degreaser...baked on.
Will bead blast these...got some of it but not a lot. Will have to scrape the rest

 

[singinwoodwackr]

Hmm, slight air leak...
I think the seal got cooked