Help, what is the proper way to rebuild the carb on my 031 it has a Tillotson HU3C-29 carb.I got a kit and took carb apart under the little plug that looks like a small soft plug there where a couple of small holes ,jets or whatever they are called they where plugged ,so I cleaned them out with a small torch tip cleaner ,they where then open .Then put carb back together and saw started and runs after tweaking needle and seat untill it stoped leaking fuel out of carb . Now it will run ,but hesitatates when u rev up at first then takes off ,but when u return to idle it wont idle right and wont adjust,and fuel leaks out.Any ideas?, should I try another carb,where should I start first ,HELP thanks Duke
Stihl 031 AV carb
- Thread starter Duke M
- Start date
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Clean, Clean, Clean!
I always completely disassemble the carb and clean it with aerosol carb cleaner (gum-out). I blow it through every opening repeatedly until the cleaner flows through unrestricted. I then replace everything that came in the kit (except the welch plugs, I've never had to pull them).
After a rebuild, there shouldn't be any fuel leaking out of the carb. One thing I did once (The first time I rebuilt a carb) was to install the diaphragm cover incorrectly. There's a small hole in the cover that needs to be positioned correctly in order to allow the diaphragm to vent properly. It just so happens that on the 031 it nees to be on the side of the mixing screws.
Since I mentioned mixing screws (H + L), did you remove them and replace them? If I remember correctly, starting position for these is 1 + 1/2 turns.
Also check for air leaks. If you have a bad fuel line, you can get hesitation like you described. My guess is you still have carb issues, but that's just me.
Also, I'm leary of sticking ANYTHING into any of the carb jets. I have never rebuilt a carb that didn't clean with cleaner. If it's too bad, buy a jug of it and soak it. Also, stay away from compressed air.
Just my 2 cents, maybe someone else will come along and give some more/better advice.
I always completely disassemble the carb and clean it with aerosol carb cleaner (gum-out). I blow it through every opening repeatedly until the cleaner flows through unrestricted. I then replace everything that came in the kit (except the welch plugs, I've never had to pull them).
After a rebuild, there shouldn't be any fuel leaking out of the carb. One thing I did once (The first time I rebuilt a carb) was to install the diaphragm cover incorrectly. There's a small hole in the cover that needs to be positioned correctly in order to allow the diaphragm to vent properly. It just so happens that on the 031 it nees to be on the side of the mixing screws.
Since I mentioned mixing screws (H + L), did you remove them and replace them? If I remember correctly, starting position for these is 1 + 1/2 turns.
Also check for air leaks. If you have a bad fuel line, you can get hesitation like you described. My guess is you still have carb issues, but that's just me.
Also, I'm leary of sticking ANYTHING into any of the carb jets. I have never rebuilt a carb that didn't clean with cleaner. If it's too bad, buy a jug of it and soak it. Also, stay away from compressed air.
Just my 2 cents, maybe someone else will come along and give some more/better advice.
Rookie1
Addicted to ArboristSite
What do you mean by fuel leaks out? Are you saying its flooding and fuel is coming back out the throat of the carb. Or is fuel leaking from gasket or fuel line.
flyboy
ArboristSite Operative
Also make sure that the lever under the metering gasket is level with the inside of the carb. You have to bend it some to make the adjustment. If it is too high, it will always be lifting the needle and I believe that will cause the fuel to leak out.
Here is the service manual (if you have the Walbro WA).
http://wem.walbro.com/distributors/servicemanuals/WAseries.pdf
Page 5 has the troubleshooting guide for flooded carbs.
The other carb is the Tillotson HU3C I believe.
Here is the service manual for that.
http://www.tillotson-fuelsystems.com/manuals.html
Here is the service manual (if you have the Walbro WA).
http://wem.walbro.com/distributors/servicemanuals/WAseries.pdf
Page 5 has the troubleshooting guide for flooded carbs.
The other carb is the Tillotson HU3C I believe.
Here is the service manual for that.
http://www.tillotson-fuelsystems.com/manuals.html
What do you mean by fuel leaks out? Are you saying its flooding and fuel is coming back out the throat of the carb. Or is fuel leaking from gasket or fuel line.
Its coming out of carb at fist it leaked out all the time ,keep teaking needle and seat until it stoped but still does some when go back to idle and wont run right ?? The lines are all new and carb is rebuilt.thanks Duke
Stihl 031AV
:newbie: Hi there to you all. I have just bought a Stihl 031AV off EBay and it won't run properly. As it was secondhand I have my reservations on how the carb was put together. The fuel line seem to be getting crushed as it's in a compacted area. Can someone give me a layout of how the fuel line is supposed to be fitted. The old pipe was cracked and leaking so I replaced it and as I stripped it to clean the carb the steel inlet pipe was moved and I'm not sure of the orientation of it as well. I can get it started by putting a few mls of fuel into the plug hole but it doesn't seem to be drawing the fuel into the diaphram area. The compression is great and the saw look as if it's been well looked after and I would like to think it's got a good few years left in it still. Any help would be much appreciated, great site by the way. All the best, Pete.l:bang:
:newbie: Hi there to you all. I have just bought a Stihl 031AV off EBay and it won't run properly. As it was secondhand I have my reservations on how the carb was put together. The fuel line seem to be getting crushed as it's in a compacted area. Can someone give me a layout of how the fuel line is supposed to be fitted. The old pipe was cracked and leaking so I replaced it and as I stripped it to clean the carb the steel inlet pipe was moved and I'm not sure of the orientation of it as well. I can get it started by putting a few mls of fuel into the plug hole but it doesn't seem to be drawing the fuel into the diaphram area. The compression is great and the saw look as if it's been well looked after and I would like to think it's got a good few years left in it still. Any help would be much appreciated, great site by the way. All the best, Pete.l:bang:
Rookie1
Addicted to ArboristSite
Good job. Its good to hear another oldie is still working.
petepetersen
ArboristSite Lurker
Is there an alternative part and/or method for replacement the fuel line in an O31AV vs using the Stihl brand fuel brand fuel /filter assembly ? - Thanks
Rookie1
Addicted to ArboristSite
Not that Im aware of. That big end that fits in the tank is kinda odd. 
petepetersen
ArboristSite Lurker
That is what I figured but it never hurts to ask . Also I would like to rebuild the carburetor . How do I tell which brand of carb it is without taking things apart (other than the cover ) to find the brand and model# - ie : the location of the adjustment needles different or other external characteristics ? - Thanks
Not that Im aware of. That big end that fits in the tank is kinda odd.
Rookie1
Addicted to ArboristSite
Usually on the side of the carb body there are letters like WA or HU and maybe some numbers.
petepetersen
ArboristSite Lurker
I have found a new in-tank fuel line assembly at a local dealer who told me that they have had it for while (several years since they sold one ). Would I be better off getting one from another dealer who has to special order it from Stihl
(fresher and refomulated "rubber" material for current gasoline blends ?)-Thanks
(fresher and refomulated "rubber" material for current gasoline blends ?)-Thanks
adkranger
Addicted to ArboristSite
I seriously doubt there is any new production of that piece considering the vintage of the saw. Old stock is the best you're going to do, be thankful they actually had a "new", unused one on a shelf.
