Let's play diagnose the farm boss chainsaw.

[VinceGU05]

so the 390's are worth keeping? mine has a fluctuating idle. WOT of fine.. just idle fast then slow. haven't looked into it yet. first port of call will be the carby. was gunna flip it and go 362 cm or carb.

 

[AKDoug]

I was visiting a 'well established' saw shop with GrizzlyAdams86. While we were there, a younger guy brought in a saw (Poulan? Really can't remember) that was acting funny. The shop owner gave it a couple of pulls, set it down on the counter, pulled out a screwdriver, and removed a totally plugged spark arrestor screen. Started the saw back up, and it appeared to run fine. He told the owner that he could clean and reinstall the screen or run it like it was, without it. "$5".

I asked him how he knew. He said, "Just sounded like it".

Philbert

We get one of those a week. You can hear them not moving exhaust through the muffler once you know what you are listening for.

 

[drf255]

I really dig the 390's if all 290's were 390's they would have a better rep

I love my 390. Not sure why so much negative feedback on them.

My muffler modded 039 keeps up with my pals 038Mag with little difficulty and weighs a lot less.

I'm not a pro logger. Since I got the 039, the 066 rarely gets taken out.

 

[Wood Doctor]

So what's left?
Here's what it was:
The plug wire was separated and corroded where it goes into the spark plug boot. I changed the coil with a used one and the saw fired right up and sounds normal. Haven't put a bar on it yet but am convinced that was the problem. This did not seem ignition related to me as the saw would consistently start but was boggy. I'll add that to my diagnostic memory bank now. Put about 5 hours of labor in figuring this issue out. The engine never "clipped" "missed" or cut out like ignition issues usually display themselves, it just ran gutless. If I was starting over, I would suspect compression and fuel. Never thought an ignition issue could feel and act like that.

I hardly would have guessed that considering that the saw started and ran but with little cutting power at WOT. Usually ignition failure hits all RPM levels and eventually the engine just conks out and won't run. On the other hand, I have also read where over half of all engine failures when compression is OK are electrically related, one way or the other.

I also have to agree with Cobey. A 290 is a weak engine waiting for a bigger bore, mod, or something to give it more grunt.

 

[fearofpavement]

I can get an 039/MS390 to cut alongside a stock 044/MS440 with a little work on it. (for a lot less $)
Of course, the 044 could be tweaked and then there would be a spread again...
The saw in this thread is an MS390. I'm going to have to pull the limiters as I can't get it rich enough. Think I'm gonna do that now as the rain has stopped, it's over 70 degrees and I've finished processing the deer.

 

[towingace]

i think old cat was pretty close then with weak spark

I suspected old-cat had it right off the bat when he got a "like" from the OP. Not only did he get, he did so before a whole lot of other variables and possibilities were eliminated.

 

[1Alpha1]

The OP gave me a like as well, and I wasn't even close to even being close.

 

[towingace]

The OP gave me a like as well, and I wasn't even close to even being close.

I thought I missed something. Actually, you were warm (you were in the ignition department) in your first post, but I'm still not seeing a "like" from the OP. Maybe I'm lost.

 

[1Alpha1]

I thought I missed something. Actually, you were warm (you were in the ignition department) in your first post, but I'm still not seeing a "like" from the OP. Maybe I'm lost.

Post #31.

BTW.....in some circles, a flux capacitor is just another term for a sparkplug cap and lead.

 

[towingace]

Post #31.

BTW.....in some circles, a flux capacitor is just another term for a sparkplug cap and lead.

I guess I'm confused (that's not hard to do), that post is after the answer was given. By the way, I don't mean to sound disrespectful to anybody, all input was valuable and good reading, that's how people like me listen and learn. I enjoy reading the humorous posts just as much as the serious ones, it's all good.

 

[1Alpha1]

I guess I'm confused (that's not hard to do), that post is after the answer was given. By the way, I don't mean to sound disrespectful to anybody, all input was valuable and good reading, that's how people like me listen and learn. I enjoy reading the humorous posts just as much as the serious ones, it's all good.

In some circles, the only sure way to make sure you answer a question correctly, is to answer after the answer has been posted.

 

[VinceGU05]

I can get an 039/MS390 to cut alongside a stock 044/MS440 with a little work on it. (for a lot less $)
Of course, the 044 could be tweaked and then there would be a spread again...
The saw in this thread is an MS390. I'm going to have to pull the limiters as I can't get it rich enough. Think I'm gonna do that now as the rain has stopped, it's over 70 degrees and I've finished processing the deer.

what "little work" is that exactly?

 

[fearofpavement]

what "little work" is that exactly?

A bit of grinding on the cylinder ports, modding the muffler, etc.

 

[fearofpavement]

$%&)##%!!!

Ok, this totally sucks. We have a do over. Went to try the saw today and it was acting almost identical to what it was doing yesterday. So although the spark plug lead issue seemed to fix it, now we're back to square one.
It so much seems like a fuel issue that I yet again tried a different carb, no go. Put the carb that was on the saw on a different one, ran fine. So I know for absolutely sure that it is not a carb.

I once again changed the spark plug. No change.

So I have checked pretty much everything and I am just wondering if it is a problem with the engine itself.
Unless, the new (used) coil/plug lead has an issue.

I just have set it aside for now and am working on a different MS390 that had a bad oiler hose, bad impulse hose and a broken impulse barb on the cylinder.
I got the new barb installed and need to reassemble the engine now. (had to open it up to pound out the broken barb)

 

[1Alpha1]

Hmmmm........I'm gonna have to think on this for a while. opcorn:

 

[dbittle]

$%&)##%!!!

Ok, this totally sucks. We have a do over. Went to try the saw today and it was acting almost identical to what it was doing yesterday. So although the spark plug lead issue seemed to fix it, now we're back to square one.
It so much seems like a fuel issue that I yet again tried a different carb, no go. Put the carb that was on the saw on a different one, ran fine. So I know for absolutely sure that it is not a carb.

I once again changed the spark plug. No change.

So I have checked pretty much everything and I am just wondering if it is a problem with the engine itself.
Unless, the new (used) coil/plug lead has an issue.

I just have set it aside for now and am working on a different MS390 that had a bad oiler hose, bad impulse hose and a broken impulse barb on the cylinder.
I got the new barb installed and need to reassemble the engine now. (had to open it up to pound out the broken barb)

Just for fun, why not swap the coil with a known good one? You've eliminated most of the usual suspects, so it is another item to cross off the list.

 

[fearofpavement]

Just for fun, why not swap the coil with a known good one? You've eliminated most of the usual suspects, so it is another item to cross off the list.

Well, swapping the coil on that saw is not too much fun... It requires a lot of disassembly. I don't really suspect the coil as the symptoms are identical to what they were before I changed the coil. And, to have a "known good" coil, I would have to remove it from a running saw, otherwise, I couldn't be sure it is good... I'm just really disappointed with this project right now. I have several other saws to work on so I can give it a rest. We had a bunch of storm damage in the area yesterday and I was hoping to complete this saw, test it and put it on the market. Guess not.

 

[Saw Dr.]

Check key again

 

[fearofpavement]

Check key again

The key is molded into the flywheel on that saw and it was fully intact. It's not hard to get it off so I suppose I can triple check it.
I've never used this saw (bought it broken).
One thing I have to consider is whether there could have been a different part put on it. I didn't notice anything out of the ordinary though. (and I've seen the inside of lots of these)

 

[Saw Dr.]

I love my 390. Not sure why so much negative feedback on them.

My muffler modded 039 keeps up with my pals 038Mag with little difficulty and weighs a lot less.

I'm not a pro logger. Since I got the 039, the 066 rarely gets taken out.

Until the wood gets big. If the 038M is in decent nick, it'll handle 28"+ bars with much more authority - as well as actually oil them.

Don't get me wrong, I happen to like the 1127 series. Shoot, I like 'em all.