Help MS 311 won't run right after rebuild

[stihltech]

So you have now performed the basic testing required for confirming a motor has no issues that would cause it to run poorly. This is exactly what a Stihl diagnosis chart (and any other 2 stroke manufacturer that provides one) is for. Now you get a carburetor and fix the saw.
Fixing carburetors is a 50/50 or less success. Corrosion inside cannot be removed by cleaning (passages). As rutterbe stated above, the carb is the final issue. Not an electrical computer, but a mechanical controlled by vacuum. Take away that control and you end up with bad operation or worse (scored piston and cylinder.)

 

[Gomofast]

I ordered the carb. I believe I found the problem within it. I think the tiny brass check valve under the metering diaphragm is bad. As I understand, it should allow fuel to flow from the metering side through the main jet into the throat of the carb. But I found that I could both suck and blow air through that little check valve - which means that it's not preventing air from coming back into that metering area when the diaphragm lifts. I think (hope) that makes sense.

 

[Gomofast]

Yep, new carb did the trick. It purrs now. Thanks all for the help.

 

[lone wolf]

One thing I've never been able to get my grasp around is how saw owners manage to straight gas any saw. I always keep my pre mix in a dedicated gas can and my straight gas for the 4 strokes in separate gas cans not anywhere near the pre mix can.

Working part time at my tractor dealer who is also an Echo dealer, I see a lot of straight gassed saws come in and I always wonder about the owners and their level of intelligence.

When the carb was done, was it rebuilt and just cleaned and were the internals reset properly?

By lending them out is one way!