044 Carb setting/ tune questions.

[Ex Umbra]

1. The manual of my 044 says to turn the carb screws in from stops a certain amount, but the sticker on the side by the carb tuning screws says something else. ?

2. There are no stops on the carb screws on my saw so what to do- I don't have a base line....?
I can turn the jets in to the seats and back them out a number of turns but I have no specs for this. (Saw is in mint factory new shape. I pulled the muffler and there is no vertical wear on the piston- the lines around the piston where it was machined in the lathe are sharp & crisp.)

3. I put a tach on my saw- she's turning 14,400! if memory serves book spec is 13,6.

Problem: I cleaned the air filter and was about to proceed to make firewood.
She's having a hard time getting to main circuit/full rpm- bogging off idle. I tried to tune it to clean it up but am having trouble cleaning it up. I have to pulse the trigger a lot to get her going.

Stock saw. I am gonna pull the carb and clean it.

If anyone could help me with an initial carb setting I'd be appreciative.

Tach question: should I tune the main circuit purely for it to run factory spec max R's....or?
In trying to tune it to "4-stroking" I never found the rev limiter.... it just kept turning more and more and more R's/

Thanks so much crew,
Umbra

 

[pioneerguy600]

On the 044 I turn both screws out one turn each to get the saw started, most often my 044`s end up with a tad less than one turn out on the H needle and just a tad over the one turn out for the L needle, this allows for easy starting and good acceleration. If you are tuning with a tach then that will determine where the H needle will end up at. The 044 coil is not rev limited, the leaner you tune the carb the higher the revs will build.

 

[Chainsaw Jim]

You want it to "four stroke" at wot, but clean up in the cut. It's usually a tad lower than factory rpm specs. I've heard they like to tune lean to clear epa inspections.

 

[Trx250r180]

Like was said yank the red caps and start with 1 turn out on noth screws.

 

[Heffalump]

I just recently had demonstrated for me exactly why one should not rely solely on a tach when tuning a chainsaw carb. On a chainsaw, a tach is a tool that provides a reference point, nothing more.

The saw should burble at WOT when not under load, and sound like a huge electric shaver in the wood. If it is not burbling at WOT with no load, then it is running too lean and will eventually cause damage. If it continues burbling in the cut, you are too rich and could be washing the lube out of the bore, and possibly cause damage.

You may find that you have to re-tune when changing bar lengths, batches of fuel, or even during severe shifts in temperature.

 

[Ironworker]

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

 

[pioneerguy600]

I just recently had demonstrated for me exactly why one should not rely solely on a tach when tuning a chainsaw carb. On a chainsaw, a tach is a tool that provides a reference point, nothing more.

The saw should burble at WOT when not under load, and sound like a huge electric shaver in the wood. If it is not burbling at WOT with no load, then it is running too lean and will eventually cause damage. If it continues burbling in the cut, you are too rich and could be washing the lube out of the bore, and possibly cause damage.

You may find that you have to re-tune when changing bar lengths, batches of fuel, or even during severe shifts in temperature.

All good points except the over rich condition won`t wash the lube out of the bore on a two stroke since the lube is mixed in with the fuel to begin with, this happens more on four strokes.

 

[Ex Umbra]

Thanks so much everyone!

The saw should burble at WOT when not under load, and sound like a huge electric shaver in the wood. If it is not burbling at WOT with no load, then it is running too lean and will eventually cause damage.

Is the burbling associated with bouncing off the rev limited that PioneerGuy just informed me I don't have (is there a disagreement here?)
... or is it just circuitry in the carb?

On the 044 I turn both screws out one turn each to get the saw started, most often my 044`s end up with a tad less than one turn out on the H needle and just a tad over the one turn out for the L needle, this allows for easy starting and good acceleration.

Does the H, L & idle screw all play off each other idle, secondary & main circuitry wise like the Weber carb in my work truck or does the idle screw on my 044 just control how much the butterfly in the carb bore remain open for idle and not mess with the H & L circuitry of the carb?

I really appreciate everyone.
Umbra

 

[Heffalump]

Is the burbling associated with bouncing off the rev limited that PioneerGuy just informed me I don't have (is there a disagreement here?)
... or is it just circuitry in the carb?

I believe the burbling is caused by a miss. Hopefully someone more knowledgeable will correct me if I am wrong, but my understanding is that when running without a load, the scavenging effects of the engine aren't working in full force. This creates some inconsistencies with the charge in the cylinder, which results in the engine firing every fourth stroke instead of every second stroke.

Wikipedia has a decent article on it. https://en.wikipedia.org/wiki/Four-stroking

 

[pioneerguy600]

A two stroke fires every time the piston comes up to TDC.
The H and L needles control the delivery of the fuel to the carb venturi/ throat. The idle screw does affect the butterfly, allowing enough air to pass by it to carry enough fuel to the cylinder. The H and L do feed off each other somewhat, setting the L screw will affect the H side so it takes a little fine tuning to get a carb tuned to a particular engine and get it to run correctly. It`s best to get the engine idling nicely to start with and then adjust the H screw with the saw under load cutting wood. Since its very hard to adjust the screw when the saw is cutting its a try cutting and stop, make a small adjustment,try cutting again and then repeat as often as necessary to get it right. After tuning for a while it becomes a very easy thing to do, your ears will tell you when its running right.

 

[MacInAction]

Stihl make great chainsaws, but the literature is sometimes subpar. There are MANY contradictions that can be found when watching videos or reading shop manuals produced by Stihl. You are correct that some of the carburetor specifications will vary. Sometimes it's because different versions of the carburetor have been released, and other times could be due to typos when translating the original documents from German to English.

Lots of good ideas above, but this suggested method can work well if the saw is in good shape. It's always best to perform vacuum/pressure checks BEFORE doing this. One small leak in an oil or pan seal can ruin an engine when revving to the upper limits. Slow tank vents can also cause catastrophic damage at high speed when ignored. Anything that causes leaning of the fuel/oil mix or slower fuel induction can and will cause some damage when ignored during the tuning process.

There may be nine different carburetors used on this model throughout production. If the number starts with C3M, with about seven versions, get rid of it. This is an outdated model, one of which has an automatic choke. The most recent models are below with the 17a being most recent.

The factory specs are slightly different for the 15b and 17a carburetors, depending on the presence of limiter caps. Begin by removing limiter caps, if present, and adjust the low and high circuits to the factory suggestions. The 15b is one turn for both screws with or without limiters. The 17a is one turn each for no limiters, and 3/4 high 1/4 low when limiters are present. Don't be surprised if the letter varies, as not all model updates are published. The saw must be started and warmed for a few minutes with low revs using 89 octane or higher fresh fuel mix. If the saw is extremely difficult to keep running, vacuum/pressure checks for all components are in order!

Start with the LA screw, and adjust it to 3,300 RPMs. Next, find the optimum point (highest possible speed at idle) on the low circuit. If the engine increases speed significantly when the optimum point is found, use the LA to reduce back to 3,300. Search for the optimum point again on the low circuit, and it should be below 3,700 RPMs before proceeding.

The low circuit needs to be enriched at this point to lower the idle speed to 2,500 RPMs. If this is not possible, a hard fault in the engine or carburetor needs to be identified before continuing!

The high circuit is adjusted next, but it needs to be enriched beyond factory settings to ensure proper cooling and lubrication of the engine components during this portion of the procedure. A lean high setting, fault in the carburetor, or engine leak during this phase will usually toast the piston/cylinder assembly!

Use 'bursts' at WOT to gauge how the engine is accelerating. Start with a few seconds per burst, working up to five seconds maximum during the process. Usage of the EDT 7 will help, as it stores the high speed results in memory. The heat generated during the phase can melt internal components in a split second!

A healthy saw should run below factory specs at this point, which is 13,500 for the 044 during one five second burst at WOT. If not, there may be a leak somewhere! If running behavior seems suddenly erratic, do not proceed without repeating vacuum/pressure diagnostics (I have seen pan seals fail a few times during quality control checks following general repairs).

If the readings are lower than advised, simply lean the high circuit in small increments, repeating a five second WOT burst afterward. On a healthy saw, it will slowly move toward the target speed after each adjustment. If this was my saw, 12, 700 would be a better rate for high speed. It can always be leaned at a later time if the plug appearance or running behavior while cutting suggests the need for adjustment.

This sequence works very well when no other hard faults are present. If the saw doesn't respond as described, full diagnostics are needed to determine the failure.

Install new limiter caps when finished, in case the EPA police inspect your saw.....

 

[Ex Umbra]

Thank so much everyone. Great info was provided here. I really appreciate it.