Introduction and a few questions

[dakotalawdog]

Hi guys. I found this board a couple weeks ago, and am grateful for the wealth of information I've found. Thought I'd introduce myself and then ask a couple questions. I live in southwest WI on about 40 acres, most of which is timbered with walnuts and a few oaks. My wife and I bought our place a couple years ago to escape the wretched hive of scum and villany that we work in every day. I bought my first saw, an MS290 about two years ago to clear some brush and cut firewood. We do almost all of our heating with wood, so it's seen some pretty heavy use. After a few months of using it, I felt it was probably a little small for as much cutting as I was doing, but overall it ran well. I also found how much fun this is! I've been slowly learning about forestry, picked up some knowledge from a friend who used to run a land-clearing business have and felled some pretty good-sized trees. It's kind of addicting!

Anyways, after two years, my 290 seized on me. She ran great until one day she started dying at idle. I see now this was a sign of impending doom, but I cleaned the air filter, adjusted the carb per the manual, ran her for another 20 minutes great, and then she quit. I brought it into the dealer, who blamed ethanol (though I wasn't so sure). I had been planning on buying a bigger saw anyways, so I picked up an MS391 - which has a lot more power than the 290 Very happy with this saw so far and it powers through some trees my 290 struggled with.

Not wanting to give up on the 290, I started doing some research on a rebuild, which brought me here. The piston was of course badly scored (pic below). I'm waiting for a new piston and hope to have it up and running shortly. Anyways, I'm not a pro with any of this, and this is the first time I've ever tried to re-build an engine. I'm pretty good working with guns, so I figured a single cylinder engine can't be too difficult to figure out. So far, I've got everything apart just fine, though we'll see if I have any leftover parts when it's back together.

Getting to the point of my post - I realize I did some things (or didn't do some things) that contributed to the death of that engine. Wanting to learn from those mistakes, I have a few questions I have't found the answer to elsewhere....

1) I did run 10% ethanol in the saw. I realize ethanol leans out the fuel mixture, though Stihl says E10 is alright. That said, I'm just planning on driving the extra 10 minutes from now on to buy non-ethanol fuel. Does octane make a difference? The only place I can get non-ethanol only has 91 octane, but I'm just curious.

2) I've read the numerous threads here on winter/summer operation settings and carb icing. My dealer said leave it on summer unless it gets REALLY cold (in WI- that means single digits or less). I'm not worried about carb icing - but could cold air, being denser, lead to a leaner running engine, higher temperatures and problems?

3) I left the carb setting as it was from the dealer and didn't have a problem until it started dying at idle. Then I adjusted it per the manual. Should I be paying closer attention to the carb settings, or just adjusting them if I have idling problems? My father in law suggested I set it richer - so the saw "bogs" when under power, then back it off leaner until it runs good under power. How should I be adjusting / checking the carb to make sure I am not running too lean?

4) Anything else glaring I'm missing that could have contributed towards this problem? Am I right to think lean fuel was the most likely culprit, or am I overlooking something? I realize Stihl makes fine equipment, and it was probably a "software" (operator) malfunction than a "hardware" problem.

Anyways, I am glad to have found such useful information on this board. Hopefully I can learn from this experience, and continue to do so. I plan on doing a lot of reading here in the future. Thanks for your help!

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[tpope]

Welcome to the forum.

I only run ethanol free gas in my small engines. Had too many issues that were related to the ethanol.

I have never changed a saw to winter.. then again I live a little to the south of ya.

I'm sure that there will be someone along with more experience with your saws than I. Enjoy the forum!

 

[gunnusmc03]

I saw all your stickers, what's your arfcom screen name lol :wink2:

 

[blsnelling]

It will not hurt your saw to run ethanol in it, as long as it's tuned for it. Storage with ethanol is another animal. Did you use a tach to tune it? That's how it's supposed to be done on a stock saw. Definitely check your fuel line for cracks. That's a common point of failure on that series of saw, and can definitely cause one to seize. Good luck, and welcome to the forum!

 

[ROWDY]

The owner's manual says to use 89 or more. I myself simply buy 92/93 pump gas with Stihl Ultra oil with a fuel stable in it and have no trouble with it.

I use summer setting like your dealer explained 99% of the time. I believe your dealer explained that correct. If my bar oil seems to be to thick for the cold weather (an example at first start), I'll go to winter for a few minutes then switch to summer Just to warm up the oil thinner.

From what you describede, I believe that you got crud or dirt in your fuel to get your carb out of adjustment.

You have a great two saw plan.

 

[Frogfarmer]

Adjusting 2-Strokes without the proper understanding is very risky. Many articles and videos are available to help learn the tuning process. Just replacing the internals of that engine is risky as well because it very likely has another possibly fuel related issue that could ruin the new parts. While the engine is out also replace the crank seals to eliminate the possibility of a bad seal. As Brad said check the lines and I would clean the carb before install. When you get it running play with the adjustments on the carb so you understand what each one does and keep in mind a 2-stroke only runs at 80% of max RPM. So if you adjust it to where it revs at its top speed it is way too lean.

 

[dakotalawdog]

I saw all your stickers, what's your arfcom screen name lol :wink2:

LOL. Same there as here, LF, m4 and a few other places. That's usually my reloading bench.


For the saw - I did not use a tach to tune it. I'll do some searching for more on tuning the carb. I was planning on cleaning the carb real good before installing and I'll double check all the fuel lines and replace the crank seals too. If anyone has anything else, let me know.