Tuning a stihl MS211 by ear and tachometer

[MatthewG]

Hi Guys,

I bought a MS211 a few months ago and think that at some stage I may modify the muffler. However, before I do this, I'd like to get more confident with tuning it and generally more knowledgeable. My hearing is not that good at figuring out slight differences in tone when my saw is running too lean/rich.

I have removed the H screw limiter cap and started playing with the adjustment, I can hear the difference when I have it very rich, but I wondered can I use my digital/contactless tachometer to fine tune it?

Other questions:
1. My manual says that the maximum revs is 13500 rpm - is that enforced by an electronic rev limiter?

2. I set my saws H screw at 3/4 turns (standard setting) and at WOT my tachometer read 12800 rpm. Am I right to assume that (since it is almost new and run in) this figure is controllable using the H screw? So if I richen it at WOT the revs will fall, and weakening it will make them rise slightly?

What I am getting at, is, because my ear isn't that great at fine tuning at WOT, could I tune the saw by:

1. setting H screw a bit rich (blubbers/fourstrokes etc.) so that the peak revs are held back by the rich mixture.

2. then lean in the H screw, but stop before the saw gets too close to the 13500 rpm maximum?

Any help with above questions, tachometer tuning, etc. much appreciated.

Thanks
Matt

[Lnewman]

There was a long discussion thread on these issues several weeks ago.

[MatthewG]

Thanks Lnewman!

Can you share the link or such so that I can find it?

Matt

[JohnG28]

http://www.madsens1.com/saw_carb_tune.htm

This is a good place to get info on tuning. There are audio files so you can hear lean to rich.

[Roundhead]

agree with John...Madsens was the most helpful for me. the main thing is that the saw "4 strokes" in the cut so that you do not damage the cylinder/piston. better to have alittle on the rich side with STIHL oil mix only.

[CTYank]

agree with John...Madsens was the most helpful for me. the main thing is that the saw "4 strokes" in the cut so that you do not damage the cylinder/piston. better to have alittle on the rich side with STIHL oil mix only.

Not really. The saw should 2-stroke in the cut, and 4-stroke lightly when you lift (reduce load.) You want optimum full load a/f ratio and a bit too rich when the load drops with attendant speed increase. That's what the 2-stroking/4-stroking stuff means. You do NOT want excessive richness @WOT under load- optimum is the target.
Last I heard Stihl oil doesn't meet current specs (IOW JASO FC/FD, ISO-L-EGD.) Many mix oils meet both, like Woodland Pro (Bailey's).

[JohnG28]

Correct, 4 stroke out of cut, not in it. I set mine up this way, then go a little more rich just for good measure. Going this way has had good results for all my saws.