Stihl 041 Farm Boss problem

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hello,

i have a 041 farm boss that i have owned since it was brand new. served me well all of these years. loaned it to my dad. and it seemed to have a problem when i got it back. that is ok, i am just trying to trouble shoot minor things before i tear into the saw. all parts are original.

got spark
gets gas
pulls over no problems

just wont start and run,

i guess first thing is to check fuel and lines for leaks then i am open for suggestions.

maybe the carb needs looking at. i am open to one and all suggestions.

thank you to the group.
michael

 

[Lakeside53]

If the plug is wet, it's probably getting too much gas and that's why it won't run. Rebuild the carb, but first check the spark under load. You may have spark outside the engine, but under pressure it may not be enough to fire. Open the spark gap to about 1/8 or 3/16 inch and see it it sparks. If so, it will work at .5mm under pressure.

If dry, it's not getting gas though the carb, OR, the impulse is not working. Try pouring a little MIX gas down the carb and see if it will fire. If it fires but won't run, then look at the impulse line, carb block screws (tighten) or carb.


Let us know what you find for the next steps..

 

[Kenskip1]

Missing

I hope that I am wrong in this assumption but is their a chance that he put straight gas through the saw? I hope not. Can you do a compression check? Did he possibly try and adjust the settings? If compression is good and spark is evident I would think about a carb kit. Mine runs like hell! Ken in colemanTx

 

[ehgauss]

Stihl 041 Farm Boss no start

I recently had a problem with my 041 Farm Boss (bought used) that sounded like yours. Used it for a couple of years cutting firewood with no problems, and then lost power several times. After that, it wouldn't start at all. Diagnosis showed good spark and it ran for a few seconds if I poured fuel directly into the carb. Bought a carb kit and tore into it. Found the small screen filter in the carb to be plugged solid. Replaced it and all the diaphragms, etc. with new from the kit and it started and has been running every day since. Luck, Gene Gauss

 

[missing]

What Steps I Have Performed.

If the plug is wet, it's probably getting too much gas and that's why it won't run. Rebuild the carb, but first check the spark under load. You may have spark outside the engine, but under pressure it may not be enough to fire. Open the spark gap to about 1/8 or 3/16 inch and see it it sparks. If so, it will work at .5mm under pressure.

If dry, it's not getting gas though the carb, OR, the impulse is not working. Try pouring a little MIX gas down the carb and see if it will fire. If it fires but won't run, then look at the impulse line, carb block screws (tighten) or carb.


Let us know what you find for the next steps..

HERE IS THE STEPS I HAVE TAKEN

took the air filter off, got a new filter, got a carb kit,

when looking at the carb, the carb is brand new, i believe my dad replaced the carb, unhooked the gas line and can blow into the carb, with no blockage, replaced gas line, old line was hard as rock, so we are removing and replacing the cheap parts first.

mixed a new batch of gasoline and oil, 50/1. filled tank up 1/2 way, adjusted hi and lo carb screws all the way in , then backed out one turn each.

put on choke, clicked on handle on all the way, pulled rope, starts up, sputters a little, pull again, starts and runs, idle low and high, seem a little off, i get it where it is not running wide open, idles down, but i cant seem to get the low speed or high to set correctly.

next, i will take the covers off of the sides of the carb and see if we have any trash or debris that may make it not run correctly, any other suggestions.

thanks

 

[missing]

removed both sides of carb,

removed both sides of carb, no trash, clean, all gaskets no holes, fine looking under magnifying glass.


put all back together, saw ran and started, had to screw with the idle setting screw since it was idling way too fast, now i seemed to have screwed too far, one way or the other, now saw will not start, hmm, just had to screw with the screw,

just a thougth what is teh setting for the idle screw

any more ideas, at this point,

HERE IS THE STEPS I HAVE TAKEN

took the air filter off, got a new filter, got a carb kit,

when looking at the carb, the carb is brand new, i believe my dad replaced the carb, unhooked the gas line and can blow into the carb, with no blockage, replaced gas line, old line was hard as rock, so we are removing and replacing the cheap parts first.

mixed a new batch of gasoline and oil, 50/1. filled tank up 1/2 way, adjusted hi and lo carb screws all the way in , then backed out one turn each.

put on choke, clicked on handle on all the way, pulled rope, starts up, sputters a little, pull again, starts and runs, idle low and high, seem a little off, i get it where it is not running wide open, idles down, but i cant seem to get the low speed or high to set correctly.

next, i will take the covers off of the sides of the carb and see if we have any trash or debris that may make it not run correctly, any other suggestions.

thanks

 

[Brushwacker]

I do most of my troubleshooting trial and error and have several suggestions. At some point you may want to quite possibly save yourself some time and have it pressure and vacume tested by an good servicing dealer. Not all of the shops around here seem to go that far with their service,but the better ones do. If you have points I would check the gap and condition. If you can pull the flywheel and check to see if the key on the shaft is sheared.
When I have a carb apart I squirt wd40 with the nozzel extension through each hole under the adjustment holes and watch to see if it exits inside the carb throat. If anything seems plugged and I cann't blast it out with the wd or light air pressure I will run thin tag wire through passages to clear out blockage. Sounds like the carb is fairly new and clean inside,but it is still possible it has something in it. Also does it have a screen in the muffler that is plugged? At some point you may want to check the piston and cylinder through the exhaust port. (My first 2 guesses of the problem would be the flywheel key or carb impulse line, but don't fail to check easy things first).
I would have to say 50 to 1 is light on oil for that saw,I run 25 to 1 in all of mine. If you service the air filter regularly and have the carb adjusted right carbon is not a problem,at least not for me. You should gain a little compression with more oil. The things I suggested are things I encountered and resolved. I am sure there is some more knowledgeable mechanics then me on this site , so listen on.

 

[ehgauss]

Stihl 041 Farm Boss no start

When I had the same problem with my 041, it would run for a few seconds and then quit if I poured a bottlecap full of fuel directly into the carburetor. I bought a carburetor kit and tore into it. I found that the small screen filter inside the carburetor was plugged solid. Everything else seemed to be in order, Replaced that from the kit, and while it was apart replaced all of the diaphragms and gaskets from the kit (but not the Welch plugs). I was careful to lay out all of the parts across the kitchen table to make sure I got them back in in the correct order. The filter screen has to be pressed in with the end of a small diameter dowel. I put it back together, cleaned out all of my fuel containers, fueled it up, gave it a couple of pulls, and it started. A little fooling with the adjustment screws got it about optimized, and it's been cutting just fine since. The carburetor rebuild isn't complicated, just make sure you lay it out to get it back together in correct order. Gene Gauss

 

[Lakeside53]

removed both sides of carb, no trash, clean, all gaskets no holes, fine looking under magnifying glass.


put all back together, saw ran and started, had to screw with the idle setting screw since it was idling way too fast, now i seemed to have screwed too far, one way or the other, now saw will not start, hmm, just had to screw with the screw,

just a thought what is the setting for the idle screw

any more ideas, at this point,

Fast running and then not settling down with carb adjustment is an indicator of an air leak or an overly lean condition.

On the 041 this can be seals, but don't forget the oil pump is inside the crank case so that can also be a leak path.

Did you make sure the carb mounting block screws were tight (these are the screws that mount the block to the cylinder, not just the carb mount screws)
?

The correct INITIAL setting for the L and H Mixture screw should be 1 turn out from gently seated. Turn up your LA screw until it the carb plate just moves. It should start with these settings. Sometimes you need to turn the L mixture a bit either way to keep it running as the engine's needs will change as it warms up. If you need say 1.5 turn out to start or run, then that's an indicator of an air leak (or bad carb needle seats).

Check your impulse pressure. Pull the impulse hose of the carb and put in a small blob of light grease on the hose. Pull the saw over and you'll see the grease get sucked into the tube if it's working.

Running the saw on 50:1 Stihl oil will be fine. Did you check your spark by snipping OFF the ground electrode on a plug to make a much larger spark gap (or just bend it vertical). Ground the body the plug to the cylinder fins. This will check the voltage much better than a standard gap (you need much higher voltage voltage at 10:1 compression than at 1 atmosphere...).

Never seen a flywheel key shear on this type of saw - it's made of tool steel and in any case, unless the wheel was loose, the key does nothing other than position the wheel prior to tightening the nut.

Definitely check your points gap... If you have a decent spark with the big gap test, it will likely start but with a bad condenser, may not keep running or as is often the case, run really bad above a few thousand rpm.

What is your compression?

 

[missing]

what are these parts

i have now rebuilt the carb, looks like the needle had some crud around it, looks red, so it may be additive or something from gone by gas years, well that is history, have replaced all seals in the carb, blown it out with wd-40

one thing, on the needle side of carb, those two little moon shaped disks, like a old moon hubcap, they are fine on the carb, the little one is indented in, could that be a problem, how does one remove them, are they just pressed on, so they have to be torn to get out to replace.

thanks

 

[missing]

More testing

reset all L & H to one out, adjusted idle screw as per lakeside.

checked vacuum lines and gas lines, new lines on both.

pulled spark plug, not wet, burning nicely. not black, not too gray, somewhere in between.

carb has new overhaul kit in. all is well, except, two moon shaped disks in carb, smaller one has indention in top of unit.

replaced all, fired it up, choke on , throttle locked, runs, remove choke, idles down and dies.

when it runs, it runs way to high. then i got the problem of saw has to be tilted to run,

the next step will be to replace the gas tank seal and while i am out there getting the parts, see if my stihl shop has the tools to pressure test and or vacuum test.

i do not have those tools to pressure or pull vacuum.

at this point, i think it is a air leak somewhere, i read one of the threads that mentioned the gas tank air leak. i am seeing the gas tank grommet as a potential source of air leak as it is old and cracked, and could be it. so we will check that on Monday when the world goes back to work and go from there. any thing i have missed or that might help run down the problem, please do not hesitate to advise or laugh,

i ask a lot of questions and learn accordingly.

thanks

 

[Lakeside53]

i have now rebuilt the carb, looks like the needle had some crud around it, looks red, so it may be additive or something from gone by gas years, well that is history, have replaced all seals in the carb, blown it out with wd-40

one thing, on the needle side of carb, those two little moon shaped disks, like a old moon hubcap, they are fine on the carb, the little one is indented in, could that be a problem, how does one remove them, are they just pressed on, so they have to be torn to get out to replace.

thanks

Those "disks" are covers for the passageways to the jets. They are pressed in and you get them out by spiking them and popping them out. A slight dent isn't an issue unless it's loose. New covers come in the kits. Generally, on the 041 HS carbs, they don't need to be removed unless you have a serious problem with varnish or corrosion.

BTW, when you rebuilt the carb, did you hook the metering arm under the head of the diaphragm? If you arm has a notch in the end, it MUST be hooked to the diaphragm. If it does not have a notch, you must have the right diaphragm (no slot on the button) or it will hang down too far and allow the saw to flood. Did you get a kit that contained a new needle, arm, covers, as well as diaphragms/gaskets?

 

[missing]

Not sure, but here is what i performed

yes, i hooked the metering arm in the slot of the needle that goes down into the carb? is this what you mean, is the head of the diaphragm the metal part in the middle of the diaphragm?

just so i am clear, replace the needle, new arm, spring under arm. then replace diaphragm on top, then gasket on top of that. i did not put the diaphragm under anything. does it go under the diaphragm so the pumping actions of the diaphragm moves the needle up and down? wild guess.

yes the kit contained new needle, arm covers, gaskets and diaphragms.