Stihl ms391 Help

[Armando]

Ok guys hope you can help. Bought this saw 2 years ago and really disappointed with it. I was told it was a professional saw. Now found out it isn't. Problem is keeps bogging down when cutting threw thick wood. Now when using for 6 hours straight it overheated. I figured out it had overheated when it stalled and wouldn't restart. I couldn't touch and part of saw other than handle. It sounded like a car engine when red lined on temp gauge
Lucky when cooled off started right up and seems to be ok
So I need some serious help or advice please. Do you guys think I should just sell this saw for a professional saw or is their some modifications I can do to increase power and run a 24 inch bar like I want.

So any advice or help would be appreciated

 

[Armando]

I also want to say that it has maintained. Has new chain. Cleaned all that stuff.
I'm just really frustrated. Latest storms were so bad I had to cut my way out of house. Needless to say this d**m saw failed me. Again. I have a johne Deere 18 inch that works perfectly. But with 18 bar it takes me forever to clear any type of path

 

[longbowch]

Sounds like the chain is dull.

 

[Andyshine77]

The best modification to any saw, is a good properly sharp chain. Just because the chain hasn't been used much, doesn't mean it's still sharp, if you cut dirt covered logs, hit a nail or cut into the ground, you now have a dull chain.

It also sounds like your saw many need to have the carb turned, a good dealer will know how to do this.

Sent from my KFSOWI using Tapatalk

 

[Armando]

The best modification to any saw, is a good properly sharp chain. Just because the chain hasn't been used much, doesn't mean it's still sharp, if you cut dirt covered logs, hit a nail or cut into the ground, you now have a dull chain.

It also sounds like your saw many need to have the carb turned, a good dealer will know how to do this.

Sent from my KFSOWI using Tapatalk

The best modification to any saw, is a good properly sharp chain. Just because the chain hasn't been used much, doesn't mean it's still sharp, if you cut dirt covered logs, hit a nail or cut into the ground, you now have a dull chain.

It also sounds like your saw many need to have the carb turned, a good dealer will know how to do this.

The best modification to any saw, is a good properly sharp chain. Just because the chain hasn't been used much, doesn't mean it's still sharp, if you cut dirt covered logs, hit a nail or cut into the ground, you now have a dull chain.

It also sounds like your saw many need to have the carb turned, a good dealer will know how to do this.

Sent from my KFSOWI using Tapatalk

Sent from my KFSOWI using Tapatalk[/QUOTE

The best modification to any saw, is a good properly sharp chain. Just because the chain hasn't been used much, doesn't mean it's still sharp, if you cut dirt covered logs, hit a nail or cut into the ground, you now have a dull chain.

It also sounds like your saw many need to have the carb turned, a good dealer will know how to do this.

Sent from my KFSOWI using Tapatalk

Just replaced the chain recently. I keep 3 new on hand. Taken to johne Deere who I bought it from. They were no help. So I took it to authorized service deptartment.
That's when I found out that my saw isn't a professional saw. The mechanic in back told me their has been lots of complaints for these saws. Really bulky and heavy and lack power. He said my only option was to buy another saw.

Why

 

[Andyshine77]

Sounds like that place just wants to sell you a saw, that you probably don't need. While the 391isn't a pro saw, it's still a good all around tool, that should easily do what you're asking of it. You need to find a better dealer and have them tune the carb. Like I said, it doesn't take long to dull a chain.

Sent from my HTC One_M8 using Tapatalk

 

[Armando]

Ok thanks. This will be stop 3 for service. 1st one was johne Deere not preferred service place. 2nd was. So I will update when I take.
I don't just understand why my 7 year old johne Deere saw that is 7 years old runs perfect. All I do is simple maintenance and chain replacements. Never one hesitated. Even when cutting threw hard wood

 

[juttree]

I ported a friend of mine and member here's 391 and he's constantly telling me how much he likes it. Even if you did a simple muffler mod it would wake it right up. I agree though, a sharp chain makes all the difference in the world.

 

[HuskyHeadDave]

It's 64 cc's pulling a 20 inch bar... If it isn't cutting great you might have the wrong chain on it if the carbs clean and it's running top range of RPM? You can run a 25" Stihl bar... Just buy Stihl skip chain... Mine pulls that like it's mad at somebody??? Well tuned running 40:1 for life!!!! Sounds like you need to find the real local saw shop! Good luck....

 

[rynosawr]

I am with HHDave above....

Muffler mod, sharp chain, good fuel, good tune, go cut.

No it isn't a pro saw, but many have been happy with these in some harsh use environments and schedules. The person who bought the MS391 that I fixed up has been very happy with it.....

 

[spudulike]

Just repaired one of these that looked like a seize and found the ball race cage had melted and been ingested in to the bore. Good news was a new piston and one new crank bearing plus a light hone on the bore sorted it out and is now back with the customer.

 

[HuskyHeadDave]

After reading about the airfilter issue in these 391 box type felt filters... I checked mine and sure enough it wasn't snapped all the way up... Guessing they can vibrate loose or out of place slightly and found a go bit of dust past the filter! I'll be keeping an eye on it... Might need to add something to help secure the filter... And I gotta clean the carb a bit... Wasn't noticeable in the running at all ... I don't want to be sucking dust and grit threw this puppy... It's still like new !!!????

 

[HuskyHeadDave]

Just repaired one of these that looked like a seize and found the ball race cage had melted and been ingested in to the bore. Good news was a new piston and one new crank bearing plus a light hone on the bore sorted it out and is now back with the customer.

Hey there, how's the plating look on the lining of these OEM Jugs? Look and feel like good quality? When you were rubbing the aluminum transfer off were you using a 320 wet/dry? Did the lining of the cylinder on these 391's standup to the "ware or scratch" test really good? As good as any newer Stihl lining you've worked with recently? Did it seem to you like there were some corners that could have been eased a little better from the factory? I've been buying Hutzl's Chinese cheap fix hubs for the non-oem option and I went into that knowing I'd be lightly porting...easing all the edges and coating with my Amsoil builders lube so they are ready out of the box to go to work. I'm seeing a lot of sloppy jugs with what I get to work on...??? Did I just become more coherent and aware of this lack of Quality Control or have the manufactures turned up production and relaxed the standards a bit? I'm interested I what you other repair guys think. I'm really to the point that I want to disasimble this new 661 to do my own QC and ease any edges and detail the ports and transfers so I'm kinda helping to make dang sure the jug is ready to run for the next twenty years! ...????

 

[spudulike]

The saw I worked on had the remains of the bearing cage mashed in to the cylinder and chucked out of the muffler so the piston looked seized and took most of the abuse but the cylinder had seize like witness marks so lightly honed with a two legged cylinder hone. Some do some don't but I do use a hone and works well for me with no issues.

I have seen the bevels on many newer ports look less bevelled than the older cylinders. I usually ease them with a diamond file, 180 and then 400 grit with a little oil and like to see a nice bevel on the edge of the ports, especially the exhaust. If porting, I often use a diamond burr in a dremel followed by the previous method. I haven't lost a ring to date and don't want to in the future.

I have noticed the 80s-90s cylinders often have very brittle plating that is easier to chip or flake off but put that down to it probably being Chrome rather than Nikasil. Not seen too many issues with the latest plating, still seems pretty hard and resilient!

 

[a. palmer jr.]

I've never owned a 391 but some of the other homeowner saws, like a 290 or 390 really benefit from having the carburetor adjusted right.