Another MS390 being stupid....

[isacguy]

Here is your pic. The one on the right looks rough, if I am looking at it correctly.View attachment 493590

They all sharpened up with the file pretty well, but hey, if it's just a chain I'll be clicking my heels with joy! I'm not super experienced sharpening chainsaws, and this chain was abused pretty badly when I got it. I tried to restore it best I could, but I'm no expert, I've only really learned from the Stihl manual. If a chain is throwing good sized chips instead of sawdust can it still be junk? I thought that was kind of the only indication was the chips thrown for criteria of a sharp chain. I can see the hump where my round file dove in and left the peak in the middle, does that matter?

Oh, I just saw your question about the seal, yes it was blowing bubbles, but they were so tiny, almost impossible to see.

 

[backhoelover]

i dont think the coil is advancing right, i have seen this before on a 390

 

[backhoelover]

stihl coils have stages in them. i have seen stihl coil do alot of weird things.

 

[HarleyT]

Yeah, if it wouldn't move your needle on your tester, it is tiny. Do you have a rim sprocket on it? If so, swap rims and try that other bar/chain.

 

[isacguy]

Yeah, if it wouldn't move your needle on your tester, it is tiny. Do you have a rim sprocket on it? If so, swap rims and try that other bar/chain.

I wish..it has a dumb spur sprocket. I've got some extras lying around, but not for this clutch size....I think. The 025/MS250 is a smaller diameter clutch right?

 

[isacguy]

stihl coils have stages in them. i have seen stihl coil do alot of weird things.

Really? Can you elaborate on that? I have another coil from the donor saw that was crushed by the tree.....I could swap it out and see. I have the Oppama spark tester, can i see the spark acting stupid while it is running if this is the case?

 

[a. palmer jr.]

I have something for you to check before you tear the saw apart: Did anyone per chance change the fuel line? If so you could have a slight kink in the fuel line right before it goes into the carburetor at the sharp bend. Sometimes the fuel gets cut off a bit resulting in less or sometimes no power. If that's the case don't replace it with a Chinese fuel line, you can use either a OEM Stihl line. Oregon makes a cheaper replacement that will also work.

 

[isacguy]

I have something for you to check before you tear the saw apart: Did anyone per chance change the fuel line? If so you could have a slight kink in the fuel line right before it goes into the carburetor at the sharp bend. Sometimes the fuel gets cut off a bit resulting in less or sometimes no power. If that's the case don't replace it with a Chinese fuel line, you can use either a OEM Stihl line. Oregon makes a cheaper replacement that will also work.

I did change out the fuel line and filter with a Stihl replacement, BUT now that I own a pressure/vac tester I can test the line for leaks with it before I rip it out. It would be an easy test to see if it got damaged in the install.....I don't use anything sharp or anything when installing lines, but hey it's easy to check. I may have kinked it too, they do go in tight sometimes.

 

[backhoelover]

only test for stages is Mdg and it has to be 2000 or newer

 

[motorman1]

Is there a chance the clutch is simply worn and slipping? perhaps it got oil / grease on it during rebuild? Can't imagine a small leak would have any affect, especially since you say you tuned it with a tach. You could easily richen it up to cover the air leak.

 

[backhoelover]

My 60 years old, was one of them in the frist Stihl gold tech class was telling me there is not tb on coil stages, they just go over it in tech class

 

[VK Johnson]

Boy howdy, as I read this, I keep thinkin' 'chain'...easy to remove and either have it professionally sharpened, or replace with one that has been sharpened by a pro, or new...I mean, under the circumstances described by the OP, that's probably the FIRST place I would have gone!

 

[isacguy]

Is there a chance the clutch is simply worn and slipping? perhaps it got oil / grease on it during rebuild? Can't imagine a small leak would have any affect, especially since you say you tuned it with a tach. You could easily richen it up to cover the air leak.

The clutch was hardly used on the saw that was smashed, I did clean it and degrease it in my parts washer, I should have mentioned that. I dressed it up with emery cloth like the manual states. I ruled that out mentally, but that doesn't mean it couldn't be the problem. All the springs were good, and there was virtually no wear on the drum or clutch. I've heard greasy clutches squealing, and seen glazed ones that aren't biting. Are there any other indicators that you could suggest I look for with the clutch?

 

[isacguy]

All right, all right guys, you win lol. I'll go buy a new chain today and we'll see if that's the problem. I'm so stubborn about paying other people to do things I think I can do myself, that's why I sharpen my own chains. Come to think of it, that's how i got into small engines to begin with. I've never had a problem with one, I usually get results when cutting wood. But at this point, I'd be happy if that is all it is. I'll update tonight with either being back to the drawing board, or eating a slice of humble pie.

 

[Conquistador3]

All right, all right guys, you win lol. I'll go buy a new chain today and we'll see if that's the problem. I'm so stubborn about paying other people to do things I think I can do myself, that's why I sharpen my own chains. Come to think of it, that's how i got into small engines to begin with. I've never had a problem with one, I usually get results when cutting wood. But at this point, I'd be happy if that is all it is. I'll update tonight with either being back to the drawing board, or eating a slice of humble pie.

That's what happened to me in the days of yore.
I hit a rock while bucking a tree (it was obviously hidden under some very convenient leaves) and then I started saying myself "Why this saw doesn't cut anymore? What's wrong with it? The chain has only a couple of trees on it... it cannot be it!".
That's when I learned what hitting a nail or a rock just once can do to a chain...

 

[RiverRat2]

Here is your pic. The one on the right looks rough, if I am looking at it correctly.

Fried!!!!! scrap metal junk,,,, major rocksville!!!!

 

[nstueve]

oh dear lordy... Where to start... Never pull a welsh plug! You're just asking for the next one to leak and cause the saw to run extremely rich and have no power. If I have a problem with the carb I use the cheap china replacements. Don't care what anyone says, they work very well with minimal problems. I would have put new seals in and added a little yamabond around the corners and not had any air leaks. If you see bubbles it will only get worse, pull it apart and seal it correctly. Check for kinks in the fuel line and impulse line. Use new OEM fuel and impulse lines and filter and pre-clean them with some gas mix. Ignitions on these saws rarely go bad. I've done over 200 rebuilds on this series and have only had a couple problems. Keep the stock timing and bolt it on with a business card to set the gap between coil and FW.

Chain, you need some work. The top plate is completely turned down. If you are getting chips its from the few that are actually sharp. I drew in the lines where you can see it bent down (blue on right) The right cutter needs to be taken down 1/3 of the length to get rid of the rolled edge. Once you are done filing you should see a nice smooth edge under the top plate and along the side plate (pink to the left). Just look and find the worst cutter and start there. Sharpen back until rolled edge is gone and you have a sharp tip to the cutting corner. Cut your depth gauge down to .025-.035 under the top plate height depending on hard or soft wood. The length of each cutter should be within 0.010 of each other for uniform strait cutting; if they aren't you'll start banking left or right 1/2 way through the cut.

If none of this makes sense... Come to the Iowa GTG in Chelsea IA and we will square you away. Or come up to my shop some weekend and I'll learn you.

 

[nstueve]

All right, all right guys, you win lol. I'll go buy a new chain today and we'll see if that's the problem. I'm so stubborn about paying other people to do things I think I can do myself, that's why I sharpen my own chains. Come to think of it, that's how i got into small engines to begin with. I've never had a problem with one, I usually get results when cutting wood. But at this point, I'd be happy if that is all it is. I'll update tonight with either being back to the drawing board, or eating a slice of humble pie.

There is a difference between dull chain not cutting and no power to cut. Even if you have a dull as snot chain a ms390 has the power to spin the chain relentlessly in the wood throwing saw dust and cutting super slow. Now if you put the chain to wood and you loose power to spin the chain you have problems producing the torque needed to spin the chain to cut.

Also your pop-off pressure could be really weak making the saw flood instead of run hard. Is your cylinder exhaust wet-ish when you're done testing? that would be an indication that too much fuel is being dumped in and causing a super rich condition making the saw bog down and loose power.

 

[turtle561]

make sure the compression release is closing properly. bubble test it.
i know huskys are supposed to close after first firing, but I worked on a ms290 whos release worked intermitantly. when I discovered this the running problems disappeared, plenty of power and no more erratic idling etc. I felt humbled by an obvious assumption.

 

[isacguy]

make sure the compression release is closing properly. bubble test it.
i know huskys are supposed to close after first firing, but I worked on a ms290 whos release worked intermitantly. when I discovered this the running problems disappeared, plenty of power and no more erratic idling etc. I felt humbled by an obvious assumption.

I did bubble test that thing when I was doing the leak down test because I forgot to close it initially Once air was hissing out, I pulled it shut, and put plenty of soapy water on it. It didn't leak thankfully. Thank you for the advice, There are so many things that can go wrong on these saws!