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What's wrong with the MS661?

odin

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Not meaning to start some sort of "kick the Stihl lovers" thread, or bash on Stihl bullsh*t, but what's the deal with the 661CM? Two seconds ago I found yet another one for sale that is listed as "needs work". I know there's been some sort of coil and/or solenoid upgrades on them, but what - on a basic level - is going wrong with them? Is it fixable (is it spendy)? Is it worth chasing one of these saws, or when they go south are they pretty much toast???
 

Funky sawman

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Semi retired logger, i had a new one a few years ago, used it for hazard tree felling and bucking, what a pain it was to take that saw back to the dealer once a week for intake, carb and ignition issues
 

odin

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Semi retired logger, i had a new one a few years ago, used it for hazard tree felling and bucking, what a pain it was to take that saw back to the dealer once a week for intake, carb and ignition issues

Ugh, yeah. No.
 

odin

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@Redbull661 can you shed some light on this for me? Is it looking like Stihl will sort out whatever the root problem is?
 

odin

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Redbull actually bought that saw from me
You gotta hand it to him. The man knows what he likes... even the "problem" children in the bunch...

All the 50/50 love/hate reports I've heard about this particular powerhead (and Mtronic in general, to a degree) have kept me pretty wary about even looking at one.
 

huskihl

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All the 50/50 love/hate reports I've heard about this particular powerhead
Which, in reality, equates to more like 95/5. We hear most of the stories of failures, but only a small percentage about the good ones.
 
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Redbull661

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661 and mtronic problems.

1. solenoid. The one they have had in all the mtronics isn't that great when it gets dirty. They have redesigned it.

the only time I've had an issue with any of the 16 or so 661s I've owned was when Scott and I were taking the carb apart trying stuff. I think it either got dirty or the o ring damaged when sitting out one of those times. The saw wouldn't idle at all. New Solenoid fixed the issue.

IMO most likely what is happening is that dirt and or saw dust is getting into the gas when refueling. The fuel filter is only going to protect you so long. I'd also guess fuel filters aren't getting changed as often as they should. Whatever the case, it equates to dirt into the solenoid. Hopefully the new solenoid will be more tolerant to dirt/saw dust. Because lets be honest, loggers just aren't going to be that careful or change fuel filters often enough.

2. the coil. The coil/control unit has been dissected in another thread on here. Turns out there is a computer board inside the thing. Like most electronics it's good, or going to go bad in the first month or so, or it's good (guys that don't use their saw very much it's not going to show up in a month). Early coils were programmed to let the saw go too lean out of a long cut. This was fixed with the 4701A coil. They have come out with a 4702 coil now but no one seems to know what the improvements if any were made.

3. the intake boot - early on they had the boot and the rubber washers inside would get dislodged. They fixed this with the "Straight" boot.

4. guys not letting the saw warm up. the mtronic seems to force you to let the saw warm up. I don't see why that is unreasonable to so many. You let a race car warm up.

5. guys not letting the saw cool down. Guys that shut down their saws right away. vapor lock comes to mind. Also if you read how the mtronic works. The coil remembers the last known conditions the saw ran in. So if you shut it down at say 7k rpm just out of the cut. And you go to start it up and idle is 3k. I assume its' not going to like that.


What I've done...

I blow off the gas cap before I open it.

On a Cold start I let the saw warm up for about 30 seconds before I start cutting. I go easy on the saw for 2-3 cuts then let er rip.

I let the saw idle for 10-20 seconds before I shut it off.

I modded the air filter cover on the bottom to let chips out. Now I use the max flow filter and have modded the MF cover on the bottom to let chips out.

That's all I've done and I haven't had problems with any of the 16 or so saws.

On funkysawmans 661 I believe he had the muffler opened up quite a bit. I changed to the muffler to one that was a tad more restrictive and did the reset procedure, it took 2-3 tanks of running but it ran fine from then on. In fact that saw ran really good. He had some time on it and I think it had loosened up (the crank)
 

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MustangMike

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I don't have a 661, but have 2 M Tronic saws, and I will add not to try to run them low of fuel. If you do, the computer will make it rich (to protect the saw from an air leak) and my 261 took about 7 tanks to return to normal. Could not do the reset, because it would not idle. Often had to pull the trigger to get it running, and not let it idle to keep it running. Was a real PITA, but it is back to normal now and I love it.

I don't do as much warm up as Red Bull, but I do always let them idle 10-20 seconds before shut down. Never changed any parts on either of them (except tune up parts), and my 362 was the first M Tron one my dealer sold.

I wish all my saws were M Tron.
 

dustinwilt68

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My local Stihl dealer hates them, he tries to discount 461 to the loggers so they buy them instead, but 1 crew likes the power of the 661, but they have a few saws sitting at his shop everytime I stop, they just rotate them in and out, dealer says they always need reprogrammed, makes me think I will never own one unless it's really cheap.
 
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