Stihl MS441 (from 2008) keeps stalling

[TheMatrix]

Hi, I'm hoping someone here can give me some advice.

I bought a Stihl MS441 in 2008, brand new. It has worked well over the years, mainly used for bucking fallen trees for firewood, but lately it hasn't been running great. Now as of today, it cuts half a log at full RPM, then just stalls unless I quickly release the throttle, wait a few seconds, remove the bar from the log, and then rev up and start again. It also seems slightly weaker than usual. It is quick to sputter when fully choked (a good thing, aka the normal starting procedure), which indicates to me that the ignition system and initial fuel delivery are ok.

I'm using fresh 93 octane gas with the Stihl "ultra" oil mix in the silver bottles.

I tried to restart it this evening to finish a few logs, and it does start, but as soon as I hit the trigger it stalls completely now. I gave up and came here.

I'm thinking the fuel pump/diaphragm is worn out/decomposed from ethanol gas over the past 17 years. Do people here agree? My research indicates the 441 only had one carb type, which should help to narrow down parts. What other carb parts should I be looking to replace after 17 years? The metering diaphragm, too?

I've been using this site just for the diagrams and part numbers: https://www.diyspareparts.com/parts/stihl/diagrams/ms441/ebc2bf47-c223-492a-954b

Thanks for any help!

 

[ZeroJunk]

If it has a muffler screen make sure it is not clogged up.
Make sure the tank vent is not clogged up.
Fuel filter.
Impulse line intact ?
Rebuild carb.

In whatever order you choose.

 

[slowcar281]

It’s most likely a fuel delivery issue. Start by pulling the carb and putting an oem kit in it. I believe it’s a walboro k10 kit. Check and clean the spark arrestor, it’s only held in with one bolt and slides out.

441’s use a 2 piece fuel line. I’d check to see if it’s soft and replace both lines and the fuel filter.

Once you get it apart you can check the impulse line as well. At this age it’s a good time to replace it and check the intake boot for any cracks.

Take lots of pictures if you aren’t familiar with a 441. The carb linkage and throttle cable routing can be very confusing if you didn’t pay attention to how it came apart.

 

[cscltd]

I’ve seen a few 441’s with ripped rubber intake boots. Check that too

 

[TheMatrix]

Thank you everyone! I see a lot of K10 kits, where is a good place to get one from? Generic stuff (like this: https://amazon.com/dp/B07HB5GN5Y ) on amazon give me the creeps...

 

[stihltech]

So the saw is now 17 years old. Give it some love- don't piecemeal!
Yes- any and all rubber parts are suspect. Many pulse and fuel hoses at that age. Pressure and vacuum test ARE A MUST-IF you want to guarantee it will last.
Do not forget fuel tank vent.
Is it the carburetor also? Most likely needs a refresh. They do not last forever. The best fuel in the world will not guarantee a carb for 17 years!
Have experienced a few cylinder gasket leaks on these.
You did not say it is a C model. That requires further discussion.

 

[TheMatrix]

441’s use a 2 piece fuel line. I’d check to see if it’s soft and replace both lines and the fuel filter.

These are molded rubber hoses, not tubing, correct? To confirm, #6 and #13 (aka impulse) in this blowup? https://www.diyspareparts.com/parts/stihl/diagrams/ms441/292e6723-cb2d-47f5-a908

The exhaust spark arrestor seems to be...gone. There is a little flat-head screw there holding down maybe a 1/2"x1/2" piece of rusted metal with a jagged edge. It looks like the arrestor itself broke off after the 90 angle.

So the saw is now 17 years old. Give it some love- don't piecemeal!
Yes- any and all rubber parts are suspect. Many pulse and fuel hoses at that age. Pressure and vacuum test ARE A MUST-IF you want to guarantee it will last.
Do not forget fuel tank vent.
Is it the carburetor also? Most likely needs a refresh. They do not last forever. The best fuel in the world will not guarantee a carb for 17 years!
Have experienced a few cylinder gasket leaks on these.
You did not say it is a C model. That requires further discussion.

Thank you! I love this saw, so I want to get it back to its best self.

This is the original model, no C or C-M.

Is there anything to check on the bar lubrication system at this age? I feel like it takes a really, really long time to go through a tank of oil lately. The chain isn't turning blue or anything, but my gut says the oiling system might be losing efficiency. I rev it in front of cardboard, and there is only the tiniest bit of oil that flings off.

My list of things to do so far:
- Carb kit. Is the cheap amazon kit ok? I don't know where to buy a quality kit, since it isn't OEM
- Replace pulse line
- Replace fuel hose
- Check intake boot
- Check/clean fuel vent
- If I can find my vacuum tool, I could do some of those tests.

Thank you to everyone who replied!

 

[slowcar281]

These are molded rubber hoses, not tubing, correct? To confirm, #6 and #13 (aka impulse) in this blowup? https://www.diyspareparts.com/parts/stihl/diagrams/ms441/292e6723-cb2d-47f5-a908

The exhaust spark arrestor seems to be...gone. There is a little flat-head screw there holding down maybe a 1/2"x1/2" piece of rusted metal with a jagged edge. It looks like the arrestor itself broke off after the 90 angle.



Thank you! I love this saw, so I want to get it back to its best self.

This is the original model, no C or C-M.

Is there anything to check on the bar lubrication system at this age? I feel like it takes a really, really long time to go through a tank of oil lately. The chain isn't turning blue or anything, but my gut says the oiling system might be losing efficiency. I rev it in front of cardboard, and there is only the tiniest bit of oil that flings off.

My list of things to do so far:
- Carb kit. Is the cheap amazon kit ok? I don't know where to buy a quality kit, since it isn't OEM
- Replace pulse line
- Replace fuel hose
- Check intake boot
- Check/clean fuel vent
- If I can find my vacuum tool, I could do some of those tests.

Thank you to everyone who replied!

Yes those 2 pieces are the fuel lines. If the spark arrestor is broken off and gone, pull the muffler and make sure it hasn’t damaged the piston and cylinder.

I wouldn’t buy any aftermarket carb kit. A walboro kit is only a few dollars more.

Pull the filter from the oil tank. If it’s clogged, clean it out and flush out the oil tank with some gasoline.