Problems with a stihl 041 or 047?

[1fatcat]

Hi everyone, I'm new here and hope I can get some tips on whats wrong with my saw. It is a stihl 041 or 047, I can't realy tell if it is a 1 or a 7?

Anyways, the saw cuts great and runs perfect until it gets good and hot (warmed up). I can make about 2-3 chops of a 20 inch log and then it will start to bog down under full throttle and full load.

I can stop cutting and feather the throttle when this happens and the saw will pick back up in power and RPM, but as soon as I put a load on it again, it will fall on its face.

So far I have replaced the air filter, checked the fuel filter (looks clean to me and I can blow through it with no restrictions) and checked the spark plug (nice light brown color).

This problem came about all at once. Was running good and strong all day Saturday and half the day on Sunday, then all of a sudden, I grabed the saw to drop the last tree of the day and about half way through the wedge cut it started acting up. I had to finish the cut with my back-up saw.

It feels like it has not lost any compression, and runs perfect until everything gets good and hot.

Any ideas?

Thanks, Scott

 

[jokers]

Hi Scott, Welcome to AS.

What makes you say that it feels like it has not lost compression? Has this occured more than once?

When you said that you can make 2-3 "chops", you reminded me of the story about the guy who brought his new chainsaw back to the dealer from whom he purchased it, complaining about how poorly it cut and what hard work it was to operate. When the dealer pulled the rope and started it, the neophyte chainsaw operator exclaimed "what`s that noise?"

Russ

 

[stihltech]

cap

Is the vent in the gas cap clean? Seen a few do this. Could be many other things, just check out previous postings. Your description reminds me of this problem.

 

[1fatcat]

OK, the reason I said it felt like it has not lost compression is because it doesn't pull over any easier than it always used to. Now I know that is not an accurate compression test, so I brought the saw to work with me today and did a compression test on it...175 psi.

And just for the record, I know how to use a chainsaw and I was not wildly "chopping" at the log with a stopped chain.

I'll have to check the fuel cap vent and get back to you, thanks for the suggestion. I kind of have doubts about the cap vent being plugged though because when it first acted up on Sunday, I immediatly thought I was running out of gas because that is about what it acted like. I pulled the gas cap off to fill it and seen a half a tank of fuel so I did not fill it, however the saw ran bad right away after checking the gas.

If the vent was not venting and created a vaccum in the tank, then the vaccum would have been released when I pulled the cap off and the saw should have run good for a little while...but it ran bad immediatly.

I let the saw cool off for an hour and tried it again, this time it ran good and strong for about 4 big cuts, then it started to loose power and RPM again.

I'm wondering if the ignition coil is breaking down when it gets hot? Did stihls have any common problems with the coil?

 

[stihltech]

coil

Yep, fairly common on an old 041. Did it ever whisker the plug? Sometimes that is a sign also. But don't forget a bad condenser can do similar things.

Get it hot and when the problem occurs, check the spark using a plug with the gap opened WAY up. That will show if the output is getting weak.

 

[1fatcat]

So is there a method to check the coil and condenser seperatly? I have a spark tester (the kind that checks killavolts), but how can I pinpoint it to a coil or condenser?

By the way, what does "whisker a spark plug" mean?

 

[stihltech]

whisker

A piece of debris will gap the electrodes. Sometimes due to debris in the engine, but I find bad coils will cause the problem. most prevalent on older point ignitions.
Check the coil killovolts, I think somewheres around 20 and above is ok. condensor should not be shorted.

 

[tree monkey]

check the screen in the carb, pump side.

 

[stihltech]

screen

Sorry, forgot about the screen. Fuel filter while you are in there.

 

[1fatcat]

I gather that the screen in the carb and the fuel filter in the tank are two different filters...not just a mix of words?

I checked the in tank filter and it is fine. I had no idea there is a filter in the carb too...I'll check that out.

The spark plug is a nice light brown, dry, with no debris crossing the gap. Looks just like the plugs from my 2 stroke 4 wheeler...perfect.

 

[bighead]

can someone explain to me what a coil and condenser are? Anyone have pics?
Also, how do u check the compression on a chain saw?