MS460 to lean

[clyde]

I can't get my 460 to rpm any lower than 13,800.  How do I get more adjustment out of the carb to richen it up.  It is adjusted all the way already.

[sawguy21]

Pull the limiter caps but you did not hear that from me :P

[spencerhenry]

my brother's saw, ms460, had the same problem. like sawguy said.

[pallis]

Yeah, do what these guys suggest.

[fishhuntcutwood]

Alot of guys will suggest using a wood screw to pull the caps, but Stihl makes a tool to pull them out.  I prefer the tool, as it' doesn't destroy the caps in the process.  There's a lug on the side of the cap that has to be aligned with the slot in the carb housing.  The tool is like $6 at a dealer.

Jeff

[clyde]

Fishhuntcutwood,
the screw will adjust more rich with the caps off?
Or do I need any new parts.  Will I need to replace the caps after, or get new ones?

[spencerhenry]

the caps simply limit how far you can back out the screw. once mixture is set, i dont think they will go back in. i took mine out of my 066. was very happy to throw them away, dont want them back.

[clyde]

On madsons web site it says that the old screws had a spring to keep tension on the screws to keep them in adjustment, and the new adjusters wont stay adjusted w/out the limiter caps in.
Any advise or experience?

[ehp]

on the 460 there is a jet inside the carb that you can change as well, your stihl dealer should have them or can order them, your high speed jet that you can adjust that has the limiter caps on them only adjust part of your high speed fuel, if you take the side of your carb apart that has your needle and seat jet you will see a small brass jet with a number on it , just use a screwdiver to take it out and up here a jet with a bigger number means a richer jet. But on most saws just take the limiters off without hurting them set the saw up and put them back on

[StihlDoc]

13,800 RPM is okay for an MS 460 and well within specification (14,000 +/- 500). If you leave the limiter caps off, there is no longer any tension/friction on the the threads of the adjustment screws and they will change settings as they screw themselves in and out from vibration.

[sawguy21]

The tool is like $6 at a dealer.
Will the dealer sell it? A poster on another forum was steamed because the dealer said he was not allowed to. And this was in Australia fer cryin out loud :

[spencerhenry]

13,800 within spec??? i dont have a 460 manual, but the only saw i own that is over 12,000, is an old 044 which is 14,000. my brother's 460 was running about the same, 13,800 and it was definitely lean. rpm could be ok, but it was lean and running hot. worst thing as far as i know for a 2 stroke.

[clyde]

13,500 is the specified rpm.  I'd rather be slightly rich than lean.
My stihl dealer nailed me for 20.00 for the limiter cap puller!

[StihlDoc]

Spec is 14,000 RPM on EPA versions. Changes were made to the crank bearings, lower con-rod bearing and combustion chamber that allow this speed. You can run richer if you want but won't be at optimum for what engine is designed for.

[clyde]

stihldoc, the plug looks a little on the white side  at 13,800.  My service manual says 13,500 for max rpm.

[StihlDoc]

STIHL saw speed spec's are "nominal" and most times optimum performance will be found within a +/- 500 R.P.M. range of the recommended engine speed. Instruction manuals will usually err on the safe side knowing that many users have a tendency to squeak the last bit of free speed out of an engine. High revs don't offer much unless you like cutting air. When the engine is loaded in a normal work environment you will find that the engine will be cranking about 10,000 R.P.M. if performing properly (speed varies with model and design).

Personally, I hate tachometers and prefer to adjust carbs to optimum performance by ear and power under under load. A tach is just a tool you can use to make sure you are within the recommended range and not over taxing the design limits of the engine. Engine speed spec's are not necessarily "gospel" but only a safe guideline.

The H screw can be adjusted by richening it (turn counterclockwise) until the engine just starts to "blubber" or not sound quite as crisp as it should. Then slowly lean out the H screw (turn clockwise) to the point where the nice "crisp" two stroke sound just begins. When you have the engine free revving and it is making that sound where it goes from "blubbering" or "four-stroking" and transitioning into a crisp "bumble bee" or two-stroke sound, you have got your mixture set in a good range for power and will still be safe from over-revving. On engines with speed governors, set the H screw so engine speed is just below or right at the governor activation point.

[clyde]

can I fit springs from older models on the jets insted of re-installing the limiter caps?

[jokers]

slowly lean out the H screw (turn clockwise) to the point where the nice "crisp" two stroke sound just begins. When you have the engine free revving and it is making that sound where it goes from "blubbering" or "four-stroking" and transitioning into a crisp "bumble bee" or two-stroke sound, you have got your mixture set in a good range for power and will still be safe from over-revving.

Hi StihlDoc,

I think that you made an excellent post with the exception of the one statement that I`m quoting. I`ve found that if the carb is set up as you describe, where you have just transitioned out of the four stroking out of the cut, the saw is till slightly lean or am I misunderstanding what you are saying?

I agree that the risk of lean siezure at this point is minimal if not moot, but if you were to tune so the saw slightly burbles at max free speed it will have more power as it cleans up and two strokes under maximum load, and then it will be optimally tuned for actual cutting.

clyde,

Wouldn`t it be simpler just to reinstall the limiters with the appropriate range after tuning than to find the correct jet screws and springs from an older carb. I normally reinstall the limiters on Stihls, you shouldn`t have to turn either screw more than just a tweak or something else is wrong.

Russ

[StihlDoc]

Russ,
Set the high speed to the point where the "four-stroking" just begins to stop with the engine free revving. You should have a crisp two-stroke sound and maybe occaisionally it "four-strokes" slightly. I guess we are saying the same thing, other than the emission compliant engines are slightly leaner. With the pre-EPA engines the normal habit would be to set with slightly more "four-stroking" but as soon as you load the engine it smoothes out. EPA engines are designed to be just slightly leaner.

Clyde, no springs are available for the adjustment screws. The screw and carb casting design do not readily accept tension springs like the carbs of pre-EPA.

[clyde]

stihldoc, It would be easier to just put springs on the screws but if that is not posible I will have to replace the limiter caps.
thanks for the help