Problematic MS661

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We have seen at least a few instances of "tuneability" issues with MTronic saws. One thread in particular stands out on the 661. That was Funky Sawman's saw. Yesterday, my 661 started stumbling and hesitating coming off idle. Actually, it's in the hands of another member. I have never experienced issues like this with a 661. They have always had lightning throttle response in my experience. The first thing I thought of was the module on the carb. Isn't that the part people have been replacing real cheap, for something like $15? Then I went in Funky's thread and see where they replaced his ignition module and intake boot. Now I'm confused. Can anyone clear this up for me? Thanks in advance.
 
Carb solenoid and coils are all I've ever had to replace on any M-Tronic saws Brad.
We're thinking it's the coil, i.e. Controller. The porting in it is tested and proven with nothing but lightening quick throttle response. Never a hint of a stumble, not in any 661 I've done. It sounds exactly like Funky's as well, which was fixed with a coil.
 
It pisses me off when you lug it all the way down to where your cutting cause you don't want it getting bashed to bits in the skidder and you go to use it and you might as well have carried a hack saw down to the timber with you.

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Sorry to hear that Brad, hopefully it is still under warranty.

Looks like Stihl hasn't successfully replaced the 066/660 yet. You know what they say though, "third time is a charm".
 
Randy when can I get mine to you. If you say jump how high?

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Man my 660 is making a nice dry sound in the bottom end and the crank now has a little play in it. I guess 19 months worth of big timber killed it.

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I don't choose the ratio. Company saw that I try and treat like my own. 50:1. Bearing melter ratio. Crush it? It's not in the woods long enough to crush it or I'd have tried.

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Here's the saw guys. Notice how throttle response is right on until about the 3:15 mark. Then at 3:28, it probably would have died had ne not let off the throttle. Of interest, it's way improved over what it was doing yesterday. My opinion, is that the saw is running too rich, both at idle and at WOT, causing an off idle bog. If this thing had a L needle, I think an 1/8 turn leaner and it would run perfectly.

I'm also curious how pig rich the saw is for the first several minutes. It won't even clean up under heavy load at first! It does get better, but is still quite rich. I'm amazed the RPMs this thing is making under load, despite running so rich. Once we get this thing sorted out, it's going to be a monster :rock2:

Most importantly, are these the symptoms you guys have seen that had defective coils and trigger units?

 
Don't worry about the richness. I've been through quite a few Mtrons and it seems to be built into their software and as they progress towards tank 8-10, depending on the work loads etc. they really start to turn on. Some of the slowest fourstrokers I've had become the fastest runners in time. And the others just keep getting better.

If my memory serves me correctly Ford had this same set up for their diesels. Wouldn't run full out until a certain mileage was met. This was 8 years ago or so and I just can't remember exactly how that worked but friends had them and they all experienced the same thing.
 
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