Chainsaw "loading up"

[legion]

What do you call loads up?

Floods out and dies?

Now that you ask, I'm not sure. All that I cut around here is smaller stuff w/ rare exceptions. Say, 16" or smaller. When I happen to be cutting a bunch of smaller stuff in the 6" on down range the saw will run for maybe 15 minutes at full tilt for 30 seconds then idle for 30 seconds or so while I get to another piece of brush to cut. I might get 15 minutes or 15 trees or so out of it...

Then it stops running.

The first time it happened I swapped the plug which didn't look too bad to me and I swapped the air cleaner which looked a little rough but not bad from what I had seen after 25 seasons of running a Stihl in the woods. It all seamed fine, really.

I pulled an easy 100 times though and got nothing.

So I let it cool completely and tried another 100 or so. I checked fuel lines, the chain brake, choke setting, cussed plenty, etc... all the stuff you're supposed to do. Got nothing but a tired arm and the sound of compression.

I took it to my favorite shop where they do the maintanance on my tractor and asked them if they'd work on a Stihl. One of the guys says 'let's have a look' and when we got back to his work bench I noticed that even though they don't sell Stihls the floor was littered with them.

He popped the saw up in a vise and with a blurr of movement that I aparently wasn't looking closely enough at he's got the plug out, yards on the pull cord a few times (might have shot some ether in the cyclinder; not sure?), stuffs the plug back in and the saw ran 100mph with it's hair on fire. Not like just burning ether either. It idled and ran at full zoot, etc., perfectly.

He handed it back and said 'no charge, Mike. It was just loaded up'. It took him maybe 4 minutes and he wouldn't even take a few bucks for the shop beer fund. I realized after I left that I really didn't know what he did; only that he said was "loaded up".

I remember hearing other people say something similar when I was a kid riding two stroke bikes but I don't remember a fix or what the problem was other than a fouled plug... which this saw didn't have.

I'm lost. Any idea?

 

[D'Animal]

Sounds like your tank vent might be plugged. I don't know the model so I can't tell you what style you have.

If the tank vent is plugged, it will do two things.
The first is the saw will act like it is running out of fuel after 12 - 15 minutes of running. This is if you start with a full tank of fuel.
The second thing it will do is not allow pressure out of the tank. The rediant heat of the engine will warm the fuel and it will expand. The extra pressure should go out the tank vent. If the vent is not working the pressure will build until it popps the inlet needle off the seat in the carburetor and it will flood the engine.

 

[legion]

Perfect ! That sounds exactly like what's happening !

...and it's an MS250. Thank you very much, D'Animal. I was juuuust about to dive into it and even bought some starting fluid tonight to see if I could get it to scream again.

 

[D'Animal]

A few other things that are just little things.

If you have to choke it to restart, it is leaning out. This means the vent could be plugged and causing a vacuum.

If you have to put it on Fast idle, it is loading up and may be just a carburetor adjustment or the tank vent could be plugged.

If it is loading up, the L screw will need turned in.
If it is leaning out, the L screw will need turned out.
Never turn it more than 1/16 of a turn at a time while adjusting.

When changing from winter fuel to summer fuel the saws can do funny things.

 

[legion]

A few other things that are just little things.

If you have to choke it to restart, it is leaning out. This means the vent could be plugged and causing a vacuum.

If you have to put it on Fast idle, it is loading up and may be just a carburetor adjustment or the tank vent could be plugged.

If it is loading up, the L screw will need turned in.
If it is leaning out, the L screw will need turned out.
Never turn it more than 1/16 of a turn at a time while adjusting.

When changing from winter fuel to summer fuel the saws can do funny things.

Much appreciated. I'll have this booger in the vise tonight and screaming in the woods this weekend.