Stihl ms 440 not running well when cold

[ChoppyChoppy]

We get plenty of saws with the owner figuring it'll need all sorts of parts. $20 later he's back to cutting wood. Just needed carb adjustment, air filter cleaned, etc.

No reason to tear stuff apart if it's not needed!

 

[Rockjock]

We get plenty of saws with the owner figuring it'll need all sorts of parts. $20 later he's back to cutting wood. Just needed carb adjustment, air filter cleaned, etc.

No reason to tear stuff apart if it's not needed!

I look at it a little different. treating the symptom and not the cause is no way to run a business. Customers get quizzed on it they left old gas in the saw, premium or regular, good oil or just something from dollar-ramma... Pulling a carb apart can often show you the issue, schmutz in the pump diaphragm, has it lost its flexibility? Joe home owner who has never had an issue with his saw will be glad to know that it has been looked over thoroughly.

 

[HarleyT]

Schmutz?
Is that Jewish gunk?

 

[mountainlake]

Really no sense in discussing anything with some one who wont adjust a carb. Steve

 

[HarleyT]

Never said that I won't/don't adjust carbs, but I advise against trying to "adjust" out a running problem, as he obviously has.

 

[crabby cooter]

sounds like carb icing to me

 

[mountainlake]

His carb could have very well needed a little more fuel for cold weather and 1/4 turn out should have made it run rich then turn back in for fine tuning. 1/4 turn out is NOT adjusting out a problem, its seeing whats going on as he found out. Steve

 

[Rockjock]

Schmutz?
Is that Jewish gunk?

Schmutz from the German Schmutzig. Meaning unclean or dirty.

 

[outdoorfan]

Lol! I'm enjoying your replies!

The saw has a "running problem", so to speak. I tried a quarter turn out on both the low and high speed jets. Nothin, notta, zippo! But that's what I expected. If you all could hear it run I'm sure you would all have guessed the same. But it's hard for me to properly and in enough detail explain the totality of the symptoms.

I've had this saw for 7 years, but I got it used in good/very good condition. I don't remember having to mess with the jets since then. For sure summer 70-90 degrees and winter 0-30's (temps that I work in, at least) haven't seemed to make a difference with the saw that I can tell. Wait, no! Really hot temps (for me) approaching 90ish tend to cause some runability issues that I have had to play with the jets with a little to try to improve. But cold weather has never been an issue. Just my experience. I have another saw that is a little more temperamental on jetting, however. It has to be "just right" to idle and run correctly. I'm not a guru like some of you that can tell when a saw has another 5% or so in it that isn't being tapped. If it runs well, then it's good enough for me. I've never had to adjust the carb from summer to winter with this saw, except for those 90 degree days.

The carb kit came in. Maybe I'll get time to work on that carb today...

 

[mountainlake]

Wait, no! Really hot temps (for me) approaching 90ish tend to cause some runability issues that I have had to play with the jets with a little to try to improve. But cold weather has never been an issue. Just my experience.

That's exactly what I was getting at, when you close the jets some for hot weather you have to open them back up when cold. Steve

 

[outdoorfan]

If I remember, the low speed jet is the only one I messed with, and I can't remember which way I turned it. Whatever adjustments I made were very small, and in some cases even ineffective.

But this current issue seems to have nothing to do with tuning.

I didn't get to doing that carb yesterday, and now I'll wait till the rest of the parts come in so I don't have my work bench tied up any longer than necessary.

Merry Christmas to you all!

 

[outdoorfan]

Sorry it's been so long and no update, like I said I would. Christmas, and people being sick has kept me down. Oh well, the other day, I finally was gonna "tear into it", only to find the spark plug had worked it's way loose (theaded but not tight). After "fixing" that issue the saw runs like it should. Gotta remember to check that more often...

 

[outdoorfan]

Well, here's another update. If only the problem with the 440 had been solved with the spark plug. Nope!!! My gut said it was more than that.

So, I checked for an air leak. Sure enough, it was the clutch side crank seal.

After the new seal, I was retuning the carb, and during one WOT run, the piston slowly and gradually seized in the cylinder. Didn't understand why, but after letting it sit for a bit, I went against my better sense and started it right back up. It ran fine. I made a few cuts, and it seemed to be fine. But there was a rattling in the cylinder.

So, I tore it down, and somehow one of the rings must have caught or failed somehow cause it was shattered, scoring the cylinder with it.

I decided to go cheap, ordering a Farmertec 52mm BB in replacement. I did a mild port job to it, and set squish around .020-.022.

Fired it up. Used it off and on for a day, running a couple tanks of gas through it. It was running and working great.

A couple days later I tried to use it again. It didn't want to start. Gave me a terrible time. After cranking and cranking, I pulled the plug. It was bone dry. Well, this intermittent issue had happened before in my struggles last fall, so I decided to try a Farmertec carburetor to see if that made any difference. Keeping in mind that I only recently went through the carb on that 440, cleaning it out and putting a kit in it. Well, go figure, but that Farmertec carb made the saw come to life. And it's been running like a banshee ever since. Very fun and sporty.