OK, So I bought the 390, now what?

[Andy1234]

Hi all,
I bought a Stihl 390 today, at a nice price, now I'd like to ask a couple of questions.
1.) I'm planning on breaking it in with 3 tanks of fuel tomorrow and some easy cutting, any other suggestions?
2.)I plan on opening up the muffler afterwards. I plan on simply cutting out a rectangular piece of the muffler to give the exhaust a straight shot out, and trim the outer cover accordingly. I plan on keeping the stock screen in place for now. Any suggestions?
3.)Do I need to adjust the fuel mixture after the muffler is cut? This is the part that I am most concerned about. How do i adjust the idle mixture to prevent over-revving? Came some one give some basic directions on adjusting the mixture screws?
Thanks in advance.
Andy1234

 

[ShoerFast]

Clean vs dirty,,,,,,

It may be just my .02 worth, but I would take the muff off while its clean.

But it would defeat the change you will feel (before vs after) , that is worth the experment! For the time vs performance traide, just what your going to do will be fine!

Yes, you will need to readjust the carb, I like just a little richer for a new saw.
But the "L" (idle) dosant have as much to do with the top end, or over-reving as the "H" screw.
*If you tweek the "H" (at wide open throttle) just a 1/16 in (clock wise)from a 4-cycl burble for a few tanks, you will be fine and it wont over rev.
Doing a search on carb adjustments might be a little confusing, Madisons (I think) may have a sound wav on what your looking for,,,, listing to the sound may be better then a thousand words here. (some members have written very good points, but intell your feel comphortable, it would be hard to sort them)

New saws and new boots are just not as much fun as they will be when there broke-in.

There is a lot of good stuff in the owners manual also.

I'm glad you bought it,,,, congrats! you will be pleased!

Kevin

* With the saw setting on a safe surface, (note things next to the chain) , and the saw at temp. (warmed up) , hold it at WOT (wide open throttle) Compare what sound you heard on the Madison's wav, as you back the "H" screw out, some were near the limit of the travel, it should make a 4 cycl "burble" , ease the screw in just about a 1/16 turn in from the burble sound,,,,,, that should be a good place to run a few tanks throught.

 

[Lakeside53]

Sorry to dampen your enthusiasm, but...

I'd just cut wood for a few weeks, or even months, at least... I wouldn't do an mods to a new saw until you're sure it's not going to have any warranty issues.

Be careful adjusting the carb if you have no experience or tools. First you are going to have to deal with the limiter caps, and after that, if you take it back to your dealer lean seized and with modded muffler, all he's going to do is sell you another saw

The 390 works fine as it is. Cut some wood, and if you like how it cuts (you will), why touch it... ?(o.k., I know why, but...).

 

[timberwolf]

Here is the link that has been posted many times before on ajusting the carb.

http://www.madsens1.com/sawtune.htm

It is a bit hard to know what to listen for at first, a tachomiter is much quicker way to get the hang of it. But a tach isn't free.

 

[Diesel JD]

If you have a warranty wait until the warranty period runs before doing any mods. Unless you are good with 2-stroke carbs leave this adjustment to a good small engine mech after teh muffler mod. the dealer may not want to do this for you so you might need to find somebody else. Otherwise...what bar and chain did it come with? If it came with the RM2 green safety chain ditch that if you are comfortable and experienced with running a saw and get a loop of yellow label 33RS for it. I run mine with a 25" bar but that might be a bit much for it. But I keep my chains very sharp and cut mostly fairly small wood. Lastly be careful and pay attention to what you are doing this is a powerful saw and the kickback tendencies are considerably increased over smaller saws. I love mine and I think you will love yours too, give it chance to break in before you make any judgements.
J.D.

 

[fishhuntcutwood]

Lakeside and J.D. make good points. Warrantee will be a concern, as a muffler mod will void it. Run the saw like normal to break it in. Don't rev it out of the cut, however. Run the saw, get used to it and get familiar with carb adjustments before you start modifying anything.

And as JD said, ditch the safety chain if that's what you have on there.

Jeff

 

[Newfie]

Cut some wood.

 

[TRUSSMAN]

If you can't adjust the carb by ear, you could get a small tach. This way you know how many rpm's you are turning, if you are to rich or to lean.
Jeff

 

[Lakeside53]

If you can't adjust the carb by ear, you could get a small tach. This way you know how many rpm's you are turning, if you are to rich or to lean.
Jeff

Good advise... unless your ear (experience) is good, a tach is your bet. You can get them from $25 (Tiny Tach) to $130 (Stihl EDT5), with a few others in between. Madsens recording is a "perfect case". Many saws never really "burble" and just change the tone. ERR on the rich side if you are unsure... and remember it's not all about the perfect WOT RPM, it's about cut time...

 

[stihltech]

rain

Gona rain on the parade, just a little bit.

Put some tanks through it, get it off warranty. The first, so you know if the mods or the breaking in made the difference.

The carb adjust, richer may not always be better. Found this out by doing it myself. Due to the internal jetting, a midrange tends to add fuel when under load. I richened the carb up and had less power in the cut. You definitly need some wood to cut for proper adjust.