ms361 carb adjustment

[wesessiah]

just about everything i can find states to get the factory setting, i should turn the low and high all the way clockwise, then back them off 1 turn... they will both only turn 3/4 of a turn. i've seen the orange things referred to as limiter caps, is a certain point in one direction equivalent to 1 turn from the stop with the limiter cap? any insight on this will be appreciated. the saw is smoking a little bit (more than typically 2 cycle) and the chain is moving some at idle, so i wanted to tune it.

 

[Bret Hart]

There are several pages in the manual for tuning this carb. One with the limiter caps on and off. Having trouble attaching the pages though. I can send the manual if it will help.

 

[wesessiah]

i actually did find a couple of pdf files, one looks older and is more detailed, and the other is on the stihl website. one says "turn the high speed screw counterclockwise as far as stop" under the standard setting, and the other, under the standard setting section, "open the high speed screw (1) one full turn" and that diagram seems to indicate open meaning counterclockwise.

 

[Bret Hart]

Here is some of the info.


Attachment still wont go.

 

[PapaDave]

I don't think the site allows pdf files, if that's what you're trying to do.

 

[Bret Hart]

The PDF is too large and I tried to copy the pages to a word document. Even tried to just paste the info into the text box.

 

[wesessiah]

thanks for trying to post that one. can you confirm if the high speed screw with the limiter cap should be turned all the way counterclockwise for the factory setting? and the low speed screw should be turned all the way clockwise, then back a 1/4 turn counterclockwise? that's what the pdf on the stihl website states. the other pdf i found, i believe to be an older version of the manual, and i'm curious if it's changed due to the epa.

 

[TreePointer]

Turning H screw to the left (counterclockwise) until it reaches its limit will not damage the saw. This makes the High jet as rich as possible. Tuning more or less beyond this position may be accomplished through tuning with a tachometer or tuning by ear (four-stroking sound out of wood, smooth sounding in wood).

If you need to tune richer than the limiter caps permit, then see the following discussion:
(broken link removed)

CAUTION: If you turn the H screw too far to the right (clockwise), your saw will run too lean and eventually will damage the piston & cylinder.

 

[wesessiah]

Turning H screw to the left (counterclockwise) until it reaches its limit will not damage the saw. This makes the High jet as rich as possible. Tuning more or less beyond this position may be accomplished through tuning with a tachometer or tuning by ear (four-stroking sound out of wood, smooth sounding in wood).

If you need to tune richer than the limiter caps permit, then see the following discussion:
(broken link removed)

CAUTION: If you turn the H screw too far to the right (clockwise), your saw will run too lean and eventually will damage the piston & cylinder.

with the limiter caps on, they will only make 3/4 of a turn. so based on what the stihl website said, the high speed limiter cap should be turned 3/4 of a turn counterclockwise, and i want to confirm that is the factory setting. tuning it this morning, it never sounded like it was getting that rich, but i think my fuel: oil mixture has been throwing me some. my other chainsaw calls for a 24:1 mixture, and it doesn't really smoke with that mixture, but the ms361 does a fair amount. i swear this 361 is the toughest saw i've ever dealt with by ear, which i've noticed other people say on other websites, so maybe that's also part of why i'm having to ask. thanks for the responses.

 

[TreePointer]

"Factory setting" doesn't mean much, as it's not uncommon for the factory to ship saws way too lean so as to meet environmental standards. The "3/4" turn described in the manual is "Standard Setting." Adjust from standard setting to your situation: elevation above sea level, type of fuel, mix ratio, etc.

I keep it simple--by using a quality modern 2-cyle oil (Stihl Ultra) at 50:1 and at least 89 octane (specification in Stihl manual) and keep it fresh for all my OPC. I have old equipment that calls for 20:1 yet it runs better (smoother, cleaner ports, less smoke) on Stihl Ultra at 50:1. Yes, the oil has improved that much.

 

[DexterDay]

Turning H screw to the left (counterclockwise) until it reaches its limit will not damage the saw. This makes the High jet as rich as possible. Tuning more or less beyond this position may be accomplished through tuning with a tachometer or tuning by ear (four-stroking sound out of wood, smooth sounding in wood).

If you need to tune richer than the limiter caps permit, then see the following discussion:
(broken link removed)


CAUTION: If you turn the H screw too far to the right (clockwise), your saw will run too lean and eventually will damage the piston & cylinder.

Pretty easy to remove caps if you want them gone. Some have used a drywall screw? Some a pick? Take your time and look carefully. Above link is a good one.

 

[wesessiah]

thanks for the replies. i should be set, glad to get confirmation of some things.

 

[StihlHead]

Do not toss those caps! They keep the carb settings in place. The trick is to remove them, trim the tabs, and reset the caps back in place. Then the H & L screws will turn 360 degrees.

The factory/EPA limit is right at the lean limit of the saw, and the H screw should really have a 1/8-1/4 turn more to run right. I have modified all the 361s I have owed this way and tuned them with a digital tach. They run better a tad richer than the H limiter allows. Note that legally a dealer cannot do this, and if they find a saw has been trimmed this way, they have to legally restore it with new limiters with the tabs. that is the law. No law prevents you from trimming the tabs and retuning the saw though.

 

[wesessiah]

Do not toss those caps! They keep the carb settings in place. The trick is to remove them, trim the tabs, and reset the caps back in place. Then the H & L screws will turn 360 degrees.

The factory/EPA limit is right at the lean limit of the saw, and the H screw should really have a 1/8-1/4 turn more to run right. I have modified all the 361s I have owed this way and tuned them with a digital tach. They run better a tad richer than the H limiter allows. Note that legally a dealer cannot do this, and if they find a saw has been trimmed this way, they have to legally restore it with new limiters with the tabs. that is the law. No law prevents you from trimming the tabs and retuning the saw though.

thanks, exactly what i was looking for. i thought it was strange that it didn't seem to really get richer by turning it out. thanks for the heads up on the dealers having to restore them too.

 

[StihlHead]

No problemo. I do all my own saw work (tuning, repair & potring) so I have never had to take one in for service, but the new EPA laws are strict on dealer service.

They set the tabs on the lean side to pass earlier EPA regs, w/o having to use fixed H jet carbs which they had for a while on a lot of pre-EPA saw models. Trim the tabs and re-set them in the saw. With the B&C on the saw, set the L & H screws to the default settings, tune the L and L/A screws and then run the H screw out until it burples/4-strokes at WOT out of the wood, and cleans up in the wood at WOT. Or use a tach. Note that the published Stihl max rev limits are 500 RPM lower than the actual engineering/factory limits for safety reasons. So on the 361 the max RPM is really 14.5k.

 

[wesessiah]

i'm a diy guy myself. i was mechanic before my current profession, so it would kill me if i did have to take something as simple as a carbureted 2 stroke small engine to a dealer and pay for labor for something. i think the toughest part of getting this thing tuned was getting the rubber screw cover back in place though is there a simple approach i've missed, or do you just have to jimmy it back in?

 

[TreePointer]

On many 2-cycle machines, I find it easiest to unbolt the carb from the saw to play with the limiter caps. Leave the caps in place on the carb while using a razor blade to shave the limiter tab off the plastic cap.

 

[wesessiah]

On many 2-cycle machines, I find it easiest to unbolt the carb from the saw to play with the limiter caps. Leave the caps in place on the carb while using a razor blade to shave the limiter tab off the plastic cap.

thanks for the tip. i was actually looking at doing that to get the plug back in the grooves.

 

[StihlHead]

I use a small screw that I have specifically for pulling the limiters (a drywall screw also works well). I drill a tiny hole in the center of the limiter, tap in the screw, pull the limiter cap, cut the tabs with the screw in place, then replace the limiters. Sometimes you have to twist the limiter to get it out and to set them in place. Pulling the carb is also an option, but that involves a lot more work on the 361. If you do pull the carb, make sure that the nuts that keep the carb are nice and tight when you put it back in place. Any looseness in the carb can mean an air leak and lean burn. Lean burning leads to overheating and subsequent engine scoring.