031 AV-Recent Rebuild

[10RBetter]

Greetings all,

I'm new to the community and recently sparked an interest in Stihl chainsaws. Long story short, I was given an older model 031AV which wouldn't start. After a quick look at the local Stihl service center, it was diagnosed with bad coil.(no spark) They also mentioned the parts were NOA but might be found on ebay. So.............off I went to locate parts on ebay and when I turned around I had 1-028, 1-031 and 1-041. All saws run except the 031, which was listed as not running for parts only.(did however mention it had a good spark) So I disassembled the 031 parts saw and retrieved good coil and gave it to the Stihl dealer to repair original 031. Got the saw back and it now runs but it bogs down when trying to throttle quickly????? I will probably take the saw back to the dealer to repair but this leads me to my original reason for this post and to get acquainted of course.

Back to the parts saw I purchased from ebay (with missing coil)......... I found a guy on ebay who rebuilds these coils along with electronic modification. I got the repaired coil back yesterday and installed in the parts saw. I also went through carb (kit) and gave the saw a good overall cleaning. Got everything back together last night so I could fire the bad boy up today. So, just 30 minutes ago, I filled her up with gas and with 3 pulls she fired up. Idle was pretty high so I adjusted back to what appears to be normal. The saw idles perfectly but when you try to throttle up quickly....it bogs just like the saw I got repaired at Stihl dealer recently. I thought maybe slight adjustment on the carb. but have no clue how to do. Any ideas?

 

[mattinky]

Welcome to AS!

Your saw is bogging because the fuel mixture is too lean. This can be caused from a carburetor needing to be adjusted, it can also be caused by a metering lever that's not adjusted properly.
There are quite a few good videos on youtube explaining how to adjust your carb.

You said you put a kit in the carb, did you check the metering lever height? This is a critical adjustment.

You might also have an air leak causing this, if this is the case no amount of carb adjustment will fix it and you will eventually seize your saw. A saw as old as an 031 could probably use new crank seals. You might also have a leaking impulse hose or fuel line. Did you replace them? If not you should, also check the rubber intake boot and make sure it's not leaking air.

 

[a. palmer jr.]

Welcome to AS!

Your saw is bogging because the fuel mixture is too lean. This can be caused from a carburetor needing to be adjusted, it can also be caused by a metering lever that's not adjusted properly.
There are quite a few good videos on youtube explaining how to adjust your carb.

You said you put a kit in the carb, did you check the metering lever height? This is a critical adjustment.

You might also have an air leak causing this, if this is the case no amount of carb adjustment will fix it and you will eventually seize your saw. A saw as old as an 031 could probably use new crank seals. You might also have a leaking impulse hose or fuel line. Did you replace them? If not you should, also check the rubber intake boot and make sure it's not leaking air.

If all the seals and hoses appear okay you can try turning the L screw out about 1/8 turn counterclockwise or so and see if it helps. Both H and L screws should be about one turn out to start with.

 

[10RBetter]

Welcome to AS!

Your saw is bogging because the fuel mixture is too lean. This can be caused from a carburetor needing to be adjusted, it can also be caused by a metering lever that's not adjusted properly.
There are quite a few good videos on youtube explaining how to adjust your carb.

You said you put a kit in the carb, did you check the metering lever height? This is a critical adjustment.

You might also have an air leak causing this, if this is the case no amount of carb adjustment will fix it and you will eventually seize your saw. A saw as old as an 031 could probably use new crank seals. You might also have a leaking impulse hose or fuel line. Did you replace them? If not you should, also check the rubber intake boot and make sure it's not leaking air.

Thanks for the welcome! After posting last night, I went back out and started the saw up again and it runs perfect. Not sure if carb needed time to work the air out or?????? Anyhow, as mentioned still have another saw(recently out of the shop) with the same problem. I will follow your recommendations and report back.

You mentioned the videos on youtube for carb info. I actually watched a really good video of carb rebuild but don't recall a specific measurement for the metering lever height except make sure it was flush or something. I carefully looked at height and appeared to be the same as described in video and therefore didn't make any adjustments. Is there another more precise way to set the height verses eyeball??

 

[10RBetter]

If all the seals and hoses appear okay you can try turning the L screw out about 1/8 turn counterclockwise or so and see if it helps. Both H and L screws should be about one turn out to start with.

Thanks for the response. Is it safe to say, or best practice (after carb rebuild) to reset the adjustments? In other words, would you position both screws all the way in (seated) and bring both out one turn and go form there?

 

[z71mike]

Thanks for the response. Is it safe to say, or best practice (after carb rebuild) to reset the adjustments? In other words, would you position both screws all the way in (seated) and bring both out one turn and go form there?

It never hurts to do a full re-tune to establish a base. Then tweak. Often.

I'm slightly OCD so there's a tuning screwdriver in my pocket every time I run a saw. Doesn't hurt to always be running perfectly.

 

[a. palmer jr.]

Thanks for the response. Is it safe to say, or best practice (after carb rebuild) to reset the adjustments? In other words, would you position both screws all the way in (seated) and bring both out one turn and go form there?

When I rebuild a carburetor I take both screws out before the cleaning begins (making sure to mark which is H and which is L) I generally take them completely apart and soak them for a short while in carb cleaner. After it is clean I put them back in, so yes, I screw them all the way in lightly and take them out 1 turn to start with. After I start the saw I fine tune them. Sometimes they run great with the basic setting.

 

[Wood Doctor]

When I rebuild a carburetor I take both screws out before the cleaning begins (making sure to mark which is H and which is L) I generally take them completely apart and soak them for a short while in carb cleaner. After it is clean I put them back in, so yes, I screw them all the way in lightly and take them out 1 turn to start with. After I start the saw I fine tune them. Sometimes they run great with the basic setting.

Now that's a good idea. Never thought about removing them completely. I do know that most hesitations from low to high-speed occur when the low-speed set screw needs to be backed out for a richer mixture. That may also mean turning up the idle a twinge as well to avoid a stall out.

 

[Karl Robbers]

Make sure the engine of the saw has warmed up before fine tuning as it will make a difference.

 

[a. palmer jr.]

Make sure the engine of the saw has warmed up before fine tuning as it will make a difference.

That's correct. I just forgot to mention the warming up part, old age I guess...

 

[10RBetter]

Its amazing what one can learn we he surrounds himself with wise people. Thanks for the help and advice.

 

[a. palmer jr.]

Some of the guys here don't recommend this but I've had good results with it: I bought a gallon of carburetor cleaner from AutoZone (Napa has it also) with a parts basket. I take the carburetors all apart and put the main carb body and both covers in the dip for about 15 minutes, take the parts out and rinse them in hot water then blow them off with compressed air. I don't dip any gaskets, springs or small items. When the parts are dry I then reassemble the carb with new kit to manufacturers specs. The specs can be found on the company's website. All the major carb makers have a website, very helpful.

 

[Wood Doctor]

Some of the guys here don't recommend this but I've had good results with it: I bought a gallon of carburetor cleaner from AutoZone (Napa has it also) with a parts basket. I take the carburetors all apart and put the main carb body and both covers in the dip for about 15 minutes, take the parts out and rinse them in hot water then blow them off with compressed air. I don't dip any gaskets, springs or small items. When the parts are dry I then reassemble the carb with new kit to manufacturers specs. The specs can be found on the company's website. All the major carb makers have a website, very helpful.

I have to wonder if that would fix a Stihl 084 that I have resting in my shop. It refuses to idle at anything below 4500 RPM. I've tried changing the carb with an older one, but that makes the situation even worse. A complete carb knockdown and clean as you describe just might be the ticket to save this saw from the landfill. Other than that, this big saw's compression is outstanding.

 

[z71mike]

I have to wonder if that would fix a Stihl 084 that I have resting in my shop. It refuses to idle at anything below 4500 RPM. I've tried changing the carb with an older one, but that makes the situation even worse. A complete carb knockdown and clean as you describe just might be the ticket to save this saw from the landfill. Other than that, this big saw's compression is outstanding.

Never landfill that saw. It'll sell in the classifieds overnight for the right price.

 

[towingace]

I have to wonder if that would fix a Stihl 084 that I have resting in my shop. It refuses to idle at anything below 4500 RPM. I've tried changing the carb with an older one, but that makes the situation even worse. A complete carb knockdown and clean as you describe just might be the ticket to save this saw from the landfill. Other than that, this big saw's compression is outstanding.

Wood you like an address to a landfill? I know of one that reincarnates after burial. In reality I know you were just kidding and that you really wouldn't do that ...... or would you?

 

[a. palmer jr.]

I have to wonder if that would fix a Stihl 084 that I have resting in my shop. It refuses to idle at anything below 4500 RPM. I've tried changing the carb with an older one, but that makes the situation even worse. A complete carb knockdown and clean as you describe just might be the ticket to save this saw from the landfill. Other than that, this big saw's compression is outstanding.

It sounds like the 084 might have an air leak. Have you checked the intake manifold, pulse hose and both crank seals? I had a saw once that had good compression, spark etc. but wouldn't run..turned out the engine crankcase had a crack in it that was hidden until I took it apart. That one had to be parted out.

 

[Wood Doctor]

It sounds like the 084 might have an air leak. Have you checked the intake manifold, pulse hose and both crank seals? I had a saw once that had good compression, spark etc. but wouldn't run..turned out the engine crankcase had a crack in it that was hidden until I took it apart. That one had to be parted out.

"... turned out the engine crankcase had a crack in it that was hidden until I took it apart."

That's my diagnosis at this point. However, it might be worth a try to clean the carb as you outlined above before giving up. These old saws are eventually going to go. I figure this one may have nearly 1,000 hours of hard use on it by sawyers feeding a sawmill. I rebuilt the entire engine (piston, rings, etc.). If not the carb, it has to be the crank seals or a cracked crankcase that I didn't see during the rebuild. Air leaks are the pits, to say the least. :bang: