# stihl 031av issues



## jgilk1 (Nov 17, 2008)

I recently got the task to rebuild(get working) a stihl 031av i have 2 saws so i will be swaping a few parts (i would like to get both running but there budget says other wise


both are for the most part complete saws (except one is missing the pull start housing)

the only difference between the 2 saws is that the complete one has no kick back guard (it was not designed to have one) and the other does.


The problem i am having is there is no fuel coming out of the carb and i have never rebuilt such a small carb (i usually rebuild lawn mower engines) neither saw has been used in about 7 years and had fuel in them that smelled like lacquer.


several questions

is the carb a walbro?
if not what carb?
what rebuild kit would i need?

Where might i find a pull start (not attached to a running saw for cheap the guy i am rebuilding it for can't/won't pay much.)


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## jgilk1 (Nov 17, 2008)

well i got the parts i needed and got the carb rebuilt and reinstalled it

the one chain saw starts up imediatly takes a fast idel then kicks down it revs up and down imediatly but if kept at a full speed it dies imediatly (it starts right back up)

any clue as to what could cause this?


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## paulr44 (Oct 14, 2008)

jgilk1 said:


> well i got the parts i needed and got the carb rebuilt and reinstalled it
> 
> the one chain saw starts up imediatly takes a fast idel then kicks down it revs up and down imediatly but if kept at a full speed it dies imediatly (it starts right back up)
> 
> any clue as to what could cause this?


From the description, you either have some problem remaining in the carb., or a vacuum leak. Couldn't hurt to check the fuel line either - an 031 is prob. 30 yrs. old, so some "rubber" components may have rotted out. Could even be the inlet needle spring in the carb. is in cockeyed - which can produce strange symptoms.

Could be a number of things. An 031 is a about three decades old, so numerous "rubber" components could be rotted, including the fuel line - just did one myself last week on an 032AV, and an AV mount also because of rot. In short, it may be sucking air somewhere.

The 031 came with two carb. offerings, Walbro or Tillotson. Service info. can be found at:
http://wem.walbro.com/distributors/servicemanuals/
http://www.tillotson.ie/till3.html (then click on Tech Info.)
Paul


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## 30yearTech (Sep 14, 2006)

If memory serves, the 031has a rubber intake and a fuel pump pulse hose, one if not both are probably torn or cracked and leaking. It's probably unlikely that you can salvage these parts from either saw, as they are probably old as paul suggested. It may also be a good idea to check the fuel hose inside the tank as it also most likely is bad as well.


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## jgilk1 (Nov 17, 2008)

(as far as content remaining in the carb i soaked it in carb cleaner for 2 hours after dissembling it)

would a lack of a muffler cause any problem?

upon your guys suggestions i will be replacing the fuel lines.



30yearTech said:


> If memory serves, the 031has a rubber intake and a fuel pump pulse hose


question about 

which is which there is a fuel hose coming out of the tank and a rubber grommet on the carb housing (this must be fuel pulse hose? from the bottom of the piston)


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## 30yearTech (Sep 14, 2006)

That's correct, the fuel pump pulse hose plugs into a nipple on the fuel pump cover of the carburetor, and the fuel line plugs in on the side.


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## paulr44 (Oct 14, 2008)

30yearTech said:


> If memory serves, the 031has a rubber intake and a fuel pump pulse hose, one if not both are probably torn or cracked and leaking. It's probably unlikely that you can salvage these parts from either saw, as they are probably old as paul suggested. It may also be a good idea to check the fuel hose inside the tank as it also most likely is bad as well.


Your memory hasn't gone yet LOL. Yes, the 030, 031 and 032 have an impulse line. On the 032 fuel line I just did (and new carb. too), the fuel hose was basically a goo. Cracks real nice now - very surprising!


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## jgilk1 (Nov 17, 2008)

ok i found the problem in the fuel tank the filter hose was as playable as putty and the filter was clogged with what appeared to be wood shavings (pure laqure) i pulled the spare chain saw apart and to my surprise it was all brand so i swaped it over and am not having stall out @ full throttle any more...

stall out is @ low rpm (idle) if i set the carb up to run as i would a weed wacker so that the clutch does not engage (and turn the blades)

It will start up and run a solid idle when i rev it up to full throttle and let off everything is fine but if i rev it up and cut i let off the trigger(gas) and it putters out.

i car restart it immediatly!

i have 3 adjustments on the carb I,H, and idle speed

which controls the low fuel setting as it seems to me when i let off the fuel pump stops pumping fuel and i have to choke it to start.

or any other suggestion? as to what might cause this new problem?


other info if needed i can set idel speed higher (the one that pushes on the throttle lever) and the saw wont "stall" out but the clutch engages and spins the chain 

by the way paulr44's Avatar 
paulr44 thanks for those links.


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## jgilk1 (Nov 17, 2008)

few adjustments i got it running correctly yeah

but noe the problem is finding a "new" muffler here locally does any one know what other saws used the o31 style muffler?


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## paulr44 (Oct 14, 2008)

jgilk1 said:


> ok i found the problem in the fuel tank the filter hose was as playable as putty and the filter was clogged with what appeared to be wood shavings (pure laqure) i pulled the spare chain saw apart and to my surprise it was all brand so i swaped it over and am not having stall out @ full throttle any more...
> 
> stall out is @ low rpm (idle) if i set the carb up to run as i would a weed wacker so that the clutch does not engage (and turn the blades)
> 
> ...


You're welcome. If it runs briefly at idle, then stalls out, it's PROBABLY the check valve in the main metering chamber and it's a pain. Either that *OR* the idle circuit is still restricted. You can check the check valve with a piece of fuel line, trimmed squarely at one end and use your mouth on the other. You put the line over the valve area, and you should be able to blow through but not draw air in. It keeps atmospheric pressure out when the unit is at idle.

With a saw this old, I still wouldn't omit the possibility of a CC vacuum leak, but the carb. is a lot easier to work with, and you've got it runnind so that's a good start!

Muffler is obsolete - I just checked dealer site.
Orig. was P/N 1113 140 0600.
You can try these sources for obsolete Stihl parts:
Ron's (Ed & Amy) 800-433-6304
Wood Cutters 716-542-9839
Luke's Mower 905-670-2129


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## jgilk1 (Nov 17, 2008)

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

item 57 is the check valve we are talking about correct?

how do would i replace it?

(which valve did i replace with the carb kit?)

should i disassemble the entire carb and soak it? (what should i soak it in?)


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## paulr44 (Oct 14, 2008)

jgilk1 said:


> http://wem.walbro.com/distributors/servicemanuals/HDAseries.pdf
> 
> item 57 is the check valve we are talking about correct?
> 
> ...


No. Item 57 is the main jet.
Item 19 is the check valve assembly.
See that same PDF, page #2, Ref# 17 i text and graphic for explanation, then page #4 showing how it has to close at idle.
Page 3 shows it open for part / full throttle operation. See last page for diagnostic info.

To change it, you'd can drill into it, thread a bolt into it and pull it out. Or, buy the puller. *BUT*,you'd want to ENSURE it's a problem before attempting to replace it, and that a new one is available.
I'd include ensuring it was running with both mixture screws open about 1 turn, and that the inlet needle valve lever height is reasonably close to specs.

For more on testing & servicing the check valve, see PDF pages 16 & 17 of
http://wem.walbro.com/distributors/servicemanuals/ServiceManual.pdf
They show the puller being used too on pg. 17.
Page 18 has more diagnostics too, but they're a little blurry.

Paul


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