Stihl MS 661 CM,a bit lean?

[skip sail]

I've got a fairly new 661,about 10 hrs use so far,and today it was a little harder to start than before. Didnt fire up after two pulls,and died a couple of times at idle. Running 33-1 fuel,using stihl oil.
Pulled the plug,and it looked a little lean to me,so took some pics.
What do you folks reckon?
I had a mate suggest that by running 33-1,instead of 50-1,the mtronic compensates and leans the saw out,not sure if that makes any sense though.

 

[skip sail]

 

[Moparmyway]

First, I would make sure the air filter is clean.
The HD2 filter can look great but be just about clogged, restricting air to the point of starving the motor

You could also pull the air filter off and try starting it, being aware of anything different.

If you have the same problem without the air filter, then I would do the reset procedure.

 

[backhoelover]

Need to hook it to mdg and check fuel rating. Also need to do pressure tech, Casey at stihl said they had problems with rubber intake on 661

 

[backhoelover]

Pressure and vac test

 

[TreeLife]

Light brown is usually a happy engine...looks like yours needs some diagnostic work

 

[bwalker]

Plug looks normal for a lower emmissions saw to me.

 

[Adirondackstihl]

What coil is on it?

 

[BuckthornBonnie]

What coil is on it?

Yep... and any change in rpm at wot?

 

[porsche965]

As above, check the air filter and re-set the Mtronic system. I've got many tanks on plugs just like that with no problem, for years, but don't have the starting problems as you stated.

I'd also take the ratio up a bit.

 

[pro94lt]

Switch to 50:1 and try it. Read around here and you'll see many issues with mtronic/autotune issues with the heavy oil ratios... but everyone here says I'm crazy lol

 

[mdavlee]

Looks a little leaner than the plug in mine. If it's got an earlier coil I don't see it changing