Longest bar on a Stihl MS390?

[Intotheether]

My MS390 was purchased in 2007 brand new, came with a 20" bar, .050 gauge and 3/8 pitch. Its a 64 cc engine.

What would be the longest bar I could run on this stock saw? It probably has maybe 50 hours on it.

Would like to stay with .050 / 3/8 chains. I have heard 27" or 28" is the biggest bar, but wanted to see if anyone else had experience with this saw.

Also, it is worth porting/opening up the muffler? I've watched a few Youtube videos, but don't want to mess up my saw.

 

[kenton.a.frank]

25 max in my opinion.


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[Ryan'smilling]

It won't be real impressive, but yeah, I'd think a 28" would be fine. You'll need to keep an eye on the bar and chain to make sure you're getting enough oil. Make sure the oiler is turned all the way up.


And yeah, open up the muffler and retune.

 

[Ryan'smilling]

It won't be real impressive, but yeah, I'd think a 28" would be fine. You'll need to keep an eye on the bar and chain to make sure you're getting enough oil. Make sure the oiler is turned all the way up.


And yeah, open up the muffler and retune.

 

[Andrew9802]

Run a full skip chain and it will handle the 28” fine.


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[user 122190]

I ran a 24 on a Husky 460, and it was great. A 390 should pull a 28 fine if it can oil the bar. To be safe, and not waste money on the 28 B&C, make sure their is an oiler upgrade for it, if needed.

 

[MS460WOODCHUCK]

Those saws respond very well to a muffler model and are a very easy muffler to do. They are way choked up

 

[CR888]

'If' you do a muff mod the sky is the limit! I'd start with a 50" & work up from there. We're talking Stihl's biggest farm saw they sell. Find a Magnum sticker and a 'Farm Boss' decal for the bar and fear no evil, large old growth will fall over at the sight of you. Contact Piltz for correct sprocket & dawgs.
OR...
Put a 20" B/C on it and get some work done that'll benefit both you & your saw.

 

[Overkill338]

We don't even run the 25" on the 390. Mainly due to the fixed output oiler.

 

[Intotheether]

We don't even run the 25" on the 390. Mainly due to the fixed output oiler.

That was my concern, oiler limitations.

Can you PM me your genereal thoughts/experiences/lessons learned from the 390? I intend to keep this saw for a while.

 

[drf255]

Open that muffler. It will turn into a different saw.

 

[a. palmer jr.]

Before you try putting a super long bar on that saw remember it's plastic you're putting it on...I think I have a 20 on my 390 with muff mod and retune...

 

[JonCraig]

I keep 20” on my 391, but did run a 24” (or is it 25? 84DL if I recall) one day in green oak. That was about the limit of what the Oiler could do. Had the be conscious of not slipping the clutch. Maybe 15 hours on the saw, so not a worn out clutch.

 

[Intotheether]

Before you try putting a super long bar on that saw remember it's plastic you're putting it on...I think I have a 20 on my 390 with muff mod and retune...

That's true, it is plastic.

With the muffler mod, I presume the main outcome is less backpressure and more RPM?
Wouldn't that cause the sprocket to turn faster and possibly outpace the fixed output ouler?

 

[user 122190]

It is complex. Power is not always faster. And engines often need backpressure to work properly.

What IS true, that "Louder seems more Powerful", and it might only seem that way. Which is for most, all the justification needed. Imaging the doey eyed and jealous envious looks of your fellow cutters as you are twice as loud then even their bigger saws.

That's true, it is plastic.

With the muffler mod, I presume the main outcome is less backpressure and more RPM?
Wouldn't that cause the sprocket to turn faster and possibly outpace the fixed output ouler?

 

[JonCraig]

The easier exhaust gets out, the more easily air & fuel can get in, so performance increase. Same concept as performance exhaust on a car.

 

[user 122190]

In a 2 stroke engine, the very basic scavenging process of a chainsaw is not so simple.

The back pressure created by the muffler keeps most of the fresh air/gas from exiting out the exhaust. Open it to much and your performance will suffer. How much is that, is not simple to answer.

The easier exhaust gets out, the more easily air & fuel can get in, so performance increase. Same concept as performance exhaust on a car.

 

[Intotheether]

The easier exhaust gets out, the more easily air & fuel can get in, so performance increase. Same concept as performance exhaust on a car.

My concern about "outpacing the fixed output oiler" you seemed to ignore.

I realize that this is not a commercial saw or a candidate to make a Hot Saw out of.

 

[user 122190]

Oiling is a concern, as already has been said many times. You'll have to discover the final answer yourself, at your expense, for your situation. Be prepared to fix, replace, or modify the oiler, or be saddled with a B&C you can't use, and again at your expense.

My concern about "outpacing the fixed output oiler" you seemed to ignore.

I realize that this is not a commercial saw or a candidate to make a Hot Saw out of.

 

[Intotheether]

Oiling is a concern, as already has been said many times. You'll have to discover the final answer yourself, at your expense, for your situation. Be prepared to fix, replace, or modify the oiler, or be saddled with a B&C you can't use, and again at your expense.

Agreed. End thread.