help! stihl 031av problem

[usmc50bmgsniper]

just purchased a stihl 031av for $20 and this thing is in mint condition, here is the problem, the saw will start up on the first or second pull but it won't rev up to full rpms and just boggs when you open the throttle up, but sometimes it will rev up when you cycle the throttle but it always goes back to bogging down. here is what i did to it, changed the gas tank filter, cleaned and set carb, the spark plug isn't running to rich or lean either so i'm confused on why it won't rev up, would bad seals cause this? please help!! would hate to get rid of this nice saw but if no one can help then it's of to ebay for the ole 031

 

[Kenskip1]

USMC,
This might be a wild shot but it seems as if you are not getting enough fuel. Could the gas line be kinked? Have you opened the Low speed jet side of this saw? The way to tell the Low from the high, is simply,the Low Speed jet is closest to the cylinder.Try and open it up, (counterclockwise) a quarter turn. HAve you checked the gas line for holes? It may be drawing in air someplace. Keep me posted, Ken!

 

[cbfarmall]

I agree with Kenskip. Somehow you're starving for fuel. Cycling the throttle allows the intake vacuum to jump, sucking fuel a little harder through the carb. If you can get the saw to idle well and consistently I doubt you have an airleak. Never hurts to change to impulse line. I hear these saws are notorious for having bad ones.

Here's my 031.

Chris B.

 

[usmc50bmgsniper]

stihl 031 problem

sorry guys the problem is still there, i just got done putting it back together and the problem is still there, no kinked lines, the lines all looked good, i took them off and stuck my finger over the other end and blew into it and it seemed to be airtight, i started both the high and low screws at 1 1/2 turns out and fiddled with them while it was running but it still bogged down. it would rev up sometimes but most of the time it would bogg, it would seem rev up more often when i would lean the low screw out but it was almost tightened up the whole ways and i didn't want to seize my saw. i pulled the plug a few times and some times it was soaked and sometimes it was white and i know that white is real bad and running to lean on a 2 stroke, it was never running a nice golden brown like a 2 stroke should well i guess that is how they should run because i have been running and jetting 2 stroke dirtbikes for many years so to me a 2 stroke is a 2 stroke but i could be wrong any more help would be greatly appreciated because if i can't get it fixed soon then off to ebay it goes

 

[usmc50bmgsniper]

stihl 031 problem

i was thinking that myself, the plug isn't new and probablly is the original bosh plug. what champion plug is interchangable with the bosh?

 

[JimL]

Re: stihl 031 problem

Originally posted by usmc50bmgsniper
i was thinking that myself, the plug isn't new and probablly is the original bosh plug. what champion plug is interchangable with the bosh?

sounds to me like a set of points and condensor is on the order,

out o time.

 

[Kenskip1]

USMC,
Rocky squirrel has the right idea. Simply you do not have a hot enough spark to ignight the mixture. This is evidant when you pulled the plug out and it was wet.Does the saw have points or electronic ignition? If you get this ignition problem solved you should have a real runner.
However on the latter side, if you only paid 20$ for this saw you may have to spend mabie three times this for a trip to the dealer. Keep me posted, Ken

 

[stihltech]

ignition

May be a job for an aftermarket ignition module. Just remember this is the saw you need to switch the positive and negative wires on the module to get the timing to advance correctly.

Did you put a kit in the carb? Did you remove the welch plugs and clean under them?
The rear of the top handle frame must be solid or it will kink the fuel hose. Ditto if the hose is too long. If the hose is too short it will pull it off. Check seal under oil pump gear, pin that drives gear under clutch sometimes wears thru and then wears thru seal. Also, if the garter spring came off back of seal lip, it will suck vacuum but hold pressure, causing this problem.

Make sure plug wire is not pinched into cylinder fins.

Hope that gives you something to go on.

 

[JimL]

Re: ignition

Originally posted by stihltech
May be a job for an aftermarket ignition module. Just remember this is the saw you need to switch the positive and negative wires on the module to get the timing to advance correctly.

Did you put a kit in the carb? Did you remove the welch plugs and clean under them?
The rear of the top handle frame must be solid or it will kink the fuel hose. Ditto if the hose is too long. If the hose is too short it will pull it off. Check seal under oil pump gear, pin that drives gear under clutch sometimes wears thru and then wears thru seal. Also, if the garter spring came off back of seal lip, it will suck vacuum but hold pressure, causing this problem.

Make sure plug wire is not pinched into cylinder fins.

Hope that gives you something to go on.

Sounds like youve worked on a few of these?

They are killing parts for these things fast. Oil cap is nla, looked one up today.
Had a junker. or several of them.

 

[stihltech]

031

one of the saws I learned on.

 

[philwarner]

I agree with Kenskip. Somehow you're starving for fuel. Cycling the throttle allows the intake vacuum to jump, sucking fuel a little harder through the carb. If you can get the saw to idle well and consistently I doubt you have an airleak. Never hurts to change to impulse line. I hear these saws are notorious for having bad ones.

Here's my 031.

Chris B.

This is an old thread, but I just spent an afternoon cleaning the carb on my own 031AV and its symptoms are similar to the one in this thread. It will start and idle all day and will rev up freely as if it is ready to go, but when I put it in a cut, it will die in about 4 seconds. After it dies I can start it again it will idle as long as I let it. I took out the pickup filter, blew through it, and it does not seem to be plugged and while the carb was out, I tried sucking fuel through the line at the carb end and got fuel flow. I had replaced the fuel line and the impulse tube last year, but I have never replaced the points or even set them and I've owned the saw from new. It is just recently that it started dying in a cut as if it was not getting enough gas. Could worn points cause these symptoms? Is it a hard job to get to the points? Any advice will be appricated as I have a large oak that I need to cut and it is too big for any of my 015s. The 015s are great little saws for an old man to handle, but the 031AV is the standby for heavier work; I even have a 36 inch bar and chain for it for the really big stuff.

 

[Fish]

Take apart the fuel filter and inspect the foam insert. If you don't find one, then it has long disintegrated, and a proper carb rebuild /going through is in order first..


What ever happened to ole Stihltech???

 

[flyboy]

I would rebuild the carb (either a Walbro WA (k10 kit) or Tillotson HU3C). At the very least replace the metering gasket and make sure the little lever in there is level with the inside of the carb.

I have had much better luck setting the carb at 1 1/4 for low and 1 1/8 for high to start.

I bet you are way too rich and gummed the plug a bit. I believe the champion plug is a rcj7y.


I have had plenty of problems with ethanol fuel in my 2 031s....so I get 100LL from the airport now and mix it 50:1 with stihl oil. Ethanol was eating my metering gaskets very quickly (1 month tops).

 

[flyboy]

If you decide you need a new condensor...you can substitue a polyester film capacitor. 0.22uF 630Volt.(you may be able to get away with a 400Volt cap and it will be smaller and easier to mount). The capacitor definately needs to be a polyester film because they can take a lot more instantaneous current than other caps. Polyester film caps are not polarized (either lead can be + or - without damage).

Vishay and Wima both make nice ones. I just soldered leads on them and installed them under the flywheel. You need the special flywheel puller to get that off. cheapstihlparts on ebay has them and they work exceedingly well.

 

[flyboy]

This is an old thread, but I just spent an afternoon cleaning the carb on my own 031AV and its symptoms are similar to the one in this thread. It will start and idle all day and will rev up freely as if it is ready to go, but when I put it in a cut, it will die in about 4 seconds. After it dies I can start it again it will idle as long as I let it. I took out the pickup filter, blew through it, and it does not seem to be plugged and while the carb was out, I tried sucking fuel through the line at the carb end and got fuel flow. I had replaced the fuel line and the impulse tube last year, but I have never replaced the points or even set them and I've owned the saw from new. It is just recently that it started dying in a cut as if it was not getting enough gas. Could worn points cause these symptoms? Is it a hard job to get to the points? Any advice will be appricated as I have a large oak that I need to cut and it is too big for any of my 015s. The 015s are great little saws for an old man to handle, but the 031AV is the standby for heavier work; I even have a 36 inch bar and chain for it for the really big stuff.

The way I understand it is that a condenser keeps the points from arching. You could start the saw with the sights off of the flywheel and the screws out of the pull starter and at night. Rev the saw up and see if you can detect any arching. If so, time for a condensor.

 

[philwarner]

Take apart the fuel filter and inspect the foam insert. If you don't find one, then it has long disintegrated, and a proper carb rebuild /going through is in order first..

I disassembled the pickup filter; the foam is intact and everything looks clean inside. I think I replaced it a few years ago when I replaced the fuel line to the carb. To check the fuel line I attached a vacuum gage at the pickup end and a Mity-vac to the carb end; it holds a vacuum at the carb end, but I get no vacuum reading on the pickup end. I can blow from the carb end and get 2 PSI pressure reading on the vacuum gage at the pickup and it holds if I seal off the tube, but I can't get the gage to show a vacuum even if I pull 20 inches of Hg at the carb end. Is there a check valve in the fuel line and if so how can it get any gas to even idle?

I disassembled both ends of the carb and blew air through the needle jets; everything there looked squeaky clean and there are no leaks in the diaphragm I can detect. I still need to check the points. Is there an on-line repair manual for these models that describes how to get to the points? I have the original owner's book and it does have exploded views, but no repair info beyond carb adjustment.

 

[flyboy]

http://www.mediafire.com/file/dnwykggj3jy/Workshop Manual Stihl 031 032.pdf

http://www.mediafire.com/file/yodmznt4zmn/stihl carburetor manual.pdf

http://www.mediafire.com/file/ufztmc...WalbroCarb.pdf

 

[philwarner]

031AV manual links and soft fuel line

Thanks for the links, flyboy. I am downloading the manual as I type this. I discovered yesterday that I can blow either way through the fuel line and used compressed air to blow some Gum-out both ways, but I can't suck air from the tank side to the carb and the tank fuel line is very soft.

I think ethanol has softened the line to the point it collapses if the vacuum is too high and while it would still idle and rev when I put it back together, it dies after a few seconds in a high speed cut. Looking at a new fuel line on-line and will call around locally to see if anyone has one on hand. I sure hope that is all it is, but these manuals will go into my chain saw binder for the future.

Thanks again, Phil

 

[philwarner]

manual link OK - Carb links invalid

http://www.mediafire.com/file/dnwykggj3jy/Workshop Manual Stihl 031 032.pdf

http://www.mediafire.com/file/yodmznt4zmn/stihl carburetor manual.pdf

http://www.mediafire.com/file/ufztmc...WalbroCarb.pdf

I got the 031/032 manual fine, but both carb manual links return an error message that it is an invalid file.

 

[flyboy]

I have had much difficulty with ethanol fuel..

I go to the local airport and get 100LL avgas. I cannot recommend this enough. 100LL will keep for a solid year or two. Also, it has a much much better smell than auto gas.....and not 1 single drop of ethanol.

Here is your carb link.....

http://wem.walbro.com/distributors/servicemanuals/WAseries.pdf