Stihl 031 gas cap vent?

[jcb1100]

This is my first post, so please be kind. First, let me say that this site is a tremendous resource for us noobs, and it is great that those of you with skills and knowledge are available to help those of us without them.

I have a Stihl 031AV from about 1978 which was my father's. It sat for a long time before I got it running. When it runs, it runs great! I plan to use it as a backup to my MS440, and for small stuff when the 440 is too big (I am not a professional and mostly cut up scrounged wood for firewood). I only intended to replace the impulse tube until I saw the oily sawdust film coating every surface inside! I don't plan a complete restoration, but I will clean it up and replace the usual parts that can go after 30 years.

My question is this. The fuel cap has a vent hole. I have the IPL (and service manual) and I can see the internal parts. I have searched here for gas cap venting issues and I know the vent can get clogged. What I haven't found is the correct way to remove the white plastic insert from the underside of the cap body without damaging either part, to check the parts inside. Does it screw out, or pry out, or something else?

Thanks for any answers. I'm sure I'll have more questions later.

Jim in Pennsylvania

 

[Fish]

Why, is the saw running poorly? What makes you want to take it apart?

 

[jcb1100]

I didn't set out to take it apart, it just worked out that way

After I got it running last year, I let it sit too long, and then it didn't run as well as it had. Mostly, it would stall if I backed off the idle speed enough to stop the chain from moving. (I have since gotten new clutch springs in case that was the issue.) It also doesn't like to re-start when it's hot.

I did a carb clean and rebuild kit. In searching this site, I saw that the impulse tube can go bad, so I got a new one. When I looked inside to replace that, all I saw was brown goo covering everything. Since everybody's saw here looks so nice in the pictures, I figured a good clean up couldn't hurt! Mostly, I didn't want any of the oily residue to be shorting out any contacts or wiring inside.

I am still debating the issue of updating to an atom, nova, or mega fire ignition module, but I at least want to check and clean the points, and test the condenser and coil while it's apart.

Thanks for the quick response!

 

[Fish]

If you see oily goo/dust around the points, then that seal may be the
culprit.

I would like you to not replace parts just as a chase, but step back and start from square one, which would entail an accurate account of what, where, and why, from the beginning.

Most go on a wild goose chase fromthe beginning, and by the time they get back to the real problem, they have spent a lot of time and money...

 

[jcb1100]

Thanks, that's good advice. That's why I'm just looking at the "usual suspects" of parts that go bad over time: fuel line and filter, impulse tube, etc., and not looking at splitting the crankcase for no apparent reason. If it ain't broke...

The brown film I'm seeing has mostly been around the coil, spark plug wire, intake manifold, the bottom of the cylinder, on the back of the fuel tank assembly, and the stop switch wire, and obviously, under the side (clutch) cover. I don't have the flywheel off, but that side seemed much cleaner under the rope starter assembly.

On second look, there is some residue below the flywheel, at the bottom of the curve in the case, but it's not everywhere. Looking through the openings in the flywheel, the points themselves seem pretty clean.