Stihl MS 661 having the bog blues

[funky sawman]

I was out on a tree removal job yesterday, I used my 661 to buck and limb a large pee pine. The saw has about 3 gallons ran through it. The saw has a bog off idle when limbing, but its not like the 562 Husqvarna bog. the 661 bog is intermittent. other than that it runs great. Using stihl ultra at 45:1 with non ethanol 91 oct fuel. I tried switching the carb heater vent to winter but no change. Another thing I noticed was even when the saw was new after a long hard cut it has a lean lope when returned to idle then after a few seconds it clears up and idles normal. WEIRD. Would it be worth the time to reset the metering arm level?

 

[funky sawman]

As for my other M-tronic saw the 241cm it runs PERFECT, have like 5 gal of fuel ran through that bugger

 

[big t double]

have you tried the reset?

 

[funky sawman]

Not sure how to reset it yet

 

[big t double]

put it in the "start" postion and let it idle like that for 90 seconds then shut if off. be quick going from "start" to "off". then restart the saw and let it idle in the run position for 60 seconds then make 5 uniform cuts in a log. some will tell you to remove the bar and chain and some will say its not necessary...im in the not necessary camp. see if that helps.

 

[funky sawman]

ok just did the reset, still bogging. It only bogs at the coming off idle after the trigger has been blipped a few times, like when your limbing. So what is sounds like is when you make a bigger cut then when it idles down it sounds lean, if at that point you hit the throttle before the saw idle has stabilized it will bog briefily then pull out of it just fine. sounds like a lean bog to me, but why does it race a little at idle after a long hard cut?

 

[Deets066]

Damn technology.....

 

[rmh3481]

>>why does it race a little at idle after a long hard cut?
Too lean.

 

[funky sawman]

No, I don't really think the problem is with the m-tronic, I had a 385xp with a tillioson carb on it that acted the same way, replaced the carb with a newer walbro and that saw ran fine. Main nozzle problem????

 

[funky sawman]

well I know its lean but WHY

 

[coltont]

That's just how the m tronic saws sound.

 

[funky sawman]

Well my 241 sounds nothing like that when it idles down, it returns to a steady idle instantly kinda like a diesel engine would

 

[MustangMike]

With the reset procedure, I would do 90 seconds at Start, shut it down. Do 90 sec on Run, shut it down. Then start it and put it in some big wood.

That is what seems to have worked with me 362 C. Good Luck with it.

 

[Moparmyway]

With the reset procedure, I would do 90 seconds at Start, shut it down. Do 90 sec on Run, shut it down. Then start it and put it in some big wood.

This is how my STihl dealer does it, and instructed me to do the same. I did the reset right away, I am not having the problems you describe with my 661r.

Did yours start to do this recently after it was running fine, or has it been doing in since you got it ?

 

[funky sawman]

It did it a little when I first bought it and has been getting progressively worse, I figured the computer just needed to adjust, but after more than 3 gallons and it's not improving, this problem is deeper than the simple m-tronic. I just reset the carb again, it actually was worse the first time I revved it to start the long cut

 

[Roll Tide]

Have you pulled the muffler amd looked at the piston to see if there is any scoring?

 

[funky sawman]

no scoring, and it has right at 160 psi compression

 

[funky sawman]

just did another test, it seems to bog more when on its side

 

[Moparmyway]

If mine were doing this, I would look over the hoses and fuel filter, make sure the tank was full - and if everything looks good and the problem didnt go away after the reset I would just tweak the fuel metering lever, especially since it happened since its life began with you.

If - at that point - my saw still had a problem, I would go right back to the dealer and ask them to look at it right now. I would watch them and wait. That might not be possible for you, but I would try to make it happen.

Now, I might just try a vac test before I took it for a trip to the dealer, its easy enough for me to do it. If you have what you need to vac test it, it might be worth it to check. I doubt there is a problem since it doesnt happen all of the time, but just checking wouldnt hurt anything.

 

[Roll Tide]

I'd take it straight back to the dealer !