Stihl 031 Problem

I purchased this saw recently. It came to my front door running but was explained to me that it had "carb" issues. After cleaning out the carb and checking the fuel system I found no obvious problem.

What do you think? I am proceeding to come up with a fix but I wanted to share my video and 031 problem with the world. This one makes you think...

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I have an 031. possibly the intake boot? Did you put a cabr kit on it after the cleaning?

I did take the intake boot off and thoroughly went over it. Didn't see any cracks or places where air might be coming in. I took a carb off another running 031 to see if the carb was the problem but same results as you see in the video above. I do have a carb repair kit for the carb on this 031.

swap coils off the running 031.

wonder if the killswitch wire might be grounding out somewhere causing it to miss kindaor weak spark . is this an old points style saw. i would also check and make sure its got a good connection at the kill switch , had and 041 that was missing and it truned out the kill switch wire was loose on the switch and was bouncing around and causing it to spit and sputter , new kill switch and rehooked the wire and a lil heat shrink on the backside to make sure the wire didnt slip back again all fixed . if its a points style saw i would clean the points real good and reset them . i use an old fingernail file to clen the points on some of my old points style saws , works real good

discounthunter said:

swap coils off the running 031.

Click to expand...

I believe we have a winner!

My 031 acts the same way except it dies after a few seconds. Mine has intermittent spark due to dirty points or bad coil. Unfortunately you have to almost completely disassemble the saw to get at the points. A good winter project for one of those days when it's too cold out to go cut wood.

I ended up replacing one part of the ignition system. Thanks for all the feedback and input. What do you think I ended up replacing?

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The spark plug

So....What was it????

The Search:
As I got under the flywheel to look at the points and condenser, I was confused as to what I was suppose to find. I have previously taken apart other 031's (points and condenser models and electronic versions) so I knew what to expect. As I looked for the round condenser, instead I found a rectangular, black capacitor screwed to a flat plate that was mounted over the hole where the original condenser sits.

The fix:
I soldered a 0.1uF cap in its place, set the points and coil gap and re-assembled the saw. What you see in "part 2" video is significant change in saw performance. I have tried contacting the original owner to find out what this saw's past was like, if any change was made to the saw with the previous owner. The cap that was mounted seemed like it came off a different saw and lacked the proper capacitance for the 031 ignition system.

Initially all signs pointed to either a fuel system problem or coil and this saw was unique in trying to identify the problem. It is my opinion the previous owner changed out the cap with one off another saw or tried to remedy a cap-fix. By doing so, the saw then gave fuel-like symptoms masking the real issue.

Thanks to the individual (you know who you are) who provided a cost-effective solution for the capacitor. Instead of paying ~$23 for a Stihl part, I was able to install an after market capacitor for less than $2. As I think about replacement parts, I wonder if the capacitor that would have come from the Stihl dealer would have been technology from the 60's/70's or if they upgrade and sell newer technology capacitors for points and condenser ignition systems.

Excellent Information

EtzCutter said:

I purchased this saw recently. It came to my front door running but was explained to me that it had "carb" issues. After cleaning out the carb and checking the fuel system I found no obvious problem.

What do you think? I am proceeding to come up with a fix but I wanted to share my video and 031 problem with the world. This one makes you think...

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Click to expand...

Our shop has chased that exact problem time and again. We are a Stihl Dealer and had old stock capacitors, and many point sets that were close but not matches to original. I cannot tell you the number of times we have been into an 031. You have helped me greatly!