MS440 wont idle

[JimmyR]

Saw starts normally and runs OK at high speed, but will kill suddenly when throttle is about half open. Cleaned carb- no help. Also when I removed gas line to remove carb a lot of gas poured out. Should tank have pressure on it? Thanks for help, Jimmy

[joe_indi]

When it runs at high speed does it sound like it is revving more than normal, with a very thin note?
If you tilt the saw to the right does it behave differently?
When this happens with the symptoms you've mentioned the cause could be a problem of poor fuel supply caused by a poorly seating valve jet (check valve).
I have uploaded images on the jet valve in the photo gallery.
First you got to get the valve jet out of the carb.
If a new one is not available, here is what you could do as a DIY job:
If the jet valve has a mesh on the open end, use a pin to carefully remove the mesh.Earlier 044 and 046 did not have the mesh so they are less prone to this problem.
Clean the old one using soap water, any solvent, soap water and finally plain water.In that order.
Dry it out by blowing air through the tiny hole on the side.
Test it by blowing and sucking air through the open end.
When you blow you should feel the valve closing and when you suck you should feel it opening.
If this does not happen, clean it once more.
It will work once the resin build up inside is washed off.
Once it works fine re-install it flush on the body,with the line on top parallel to the H screw.
Open the L and H screws to their stops(if with limiter caps)
Screw in to their seats and turn out H=1 turn and L=1 1/2 turn (yes 1 1/2 turn).
Now try starting up. Blip the throttle till the idle starts dropping towards a stall.
Close the L screw gradually till the saw idles.
Now hold the throttle at the position a little above the speed at which the chain starts rotating.
Turn in the L screw just to the point where the engine speed starts to rise.
Adjust the idle screw if the idle speed has increased too much.
Try the saw out now.
If you find that at full throttle you have too much 4 stroking, close the H screw slightly, but not too much.

Joe

[AdkStihl]

 

[JimmyR]

Joe thanks for the help. I ran the engine today, runs same in any position. At full throttle it does sound like on the lean side. when I blip the throttle from open to closed rapidly engine speed follows the throttle with no hesitation, but if I am slow in opening the throttle at low rpm the then engine kills. Seems to me the mixture go very rich at low RPM.
I plan to pull the carb tomorrow and clean, including the jet-valve.

Jimmy

[JimmyR]

Joe_indi, pulled card and gave it a good cleaning, reinstalled and it ran with same problem. pulled carb again and punched out the jet value and cleaned per you instruction. Saw runs great now.
Many thanks Jimmy

[fuzzybear]

Joe,
  I must say that I am very impressed with your knowledge and the way you pass it on to others. Keep up the good work. The FF is lucky to have you.
FB