MS 440 Issues

[bvaught]

I cranked my 440 last night to cut a small oak. I let it idle for less than an minute and it cut off. I cranked it again and after a second or two it cut off again. Pulled and pulled, but no start.......Spark Plug????

I changed the plug and the saw fired to life. I am surprised that I fouled a plug after having done so little work with the saw...probably 5-10 running hours max. It was exceptionally damp yesterday (visible fog and light rain), and the last half hour of running was at part throttle trimming bushes in the yard.

One culprit may be my low speed adjustment. When I adjust it I find that the leaner I set the screw the better the saw runs, but Im afraid to set it full lean. So I go lean to best idle, rich to rough idle and settle for a little rough on the rich side.

 

[infomet]

I don't have anything that big, but I don't think you can hurt the saw at idle.
You can flood it and foul the plug, however. Set idle for smooth running and not loading up.
You may have just cleared a flood. Blow off the plug and see if it will start.
One good cut should clean it up.
Wilson

 

[Lakeside53]

lean it out slightly..

 

[MacDaddy]

leave it on high idle when you set it down and you wont have a problem JJ

 

[ShoerFast]

bvaught
If the conditions are just right, cool and damp, the very low pressure and fast pressure drop on the back side of the throttle valve can cause water vaper to frezze.
Stihl had seen this for a long time now and your saw should have a damper so to speek, inbetween the air filter box and cylinder, by fliping it around, you will allow some of the carbs air come off the heated cylinder. Heated air is dryer and warmer air wont drop bellow 32 deg. and may help your stalling?
As a test of a saws tune, that baffle can be fliped on a good day to see it what a little leaner then the limit stops would run like.

 

[bvaught]

bvaught
If the conditions are just right, cool and damp, the very low pressure and fast pressure drop on the back side of the throttle valve can cause water vaper to frezze.
Stihl had seen this for a long time now and your saw should have a damper so to speek, inbetween the air filter box and cylinder, by fliping it around, you will allow some of the carbs air come off the heated cylinder. Heated air is dryer and warmer air wont drop bellow 32 deg. and may help your stalling?
As a test of a saws tune, that baffle can be fliped on a good day to see it what a little leaner then the limit stops would run like.

My saw doesnt have the heated intake flapper, but there is an carb heat intake inlet that always stays open.

The carb ice issue was worth noting in this thread, but I seriously doubt that was the culprit in this situation due to the short duration from start to engine failure.

 

[Lakeside53]

The 440 does have a summer/winter positon inside the filter cover. You should open it below 50 and close it above 68 according to Stihl owners manual to "avoid engine running problems and overheating".

 

[thompson1600]

I agree with Lakeside, I'd lean the carb out on the L side.

Also, I don't know if it's just me, but lately I've been getting at least 1 plug out of a box of 10 that is/goes bad right away.

Tom

 

[bvaught]

The 440 does have a summer/winter positon inside the filter cover. You should open it below 50 and close it above 68 according to Stihl owners manual to "avoid engine running problems and overheating".

Yes, I have seen this statement in the owners manual. However my saw does not have this flap. Somewhere in the same manual I remember seeing another schematic diagram of a different air filter housing that has the constantly open hole like mine. My saw is equipped with the Heavy Duty air filter and I think that has something to do with the lack of a flap.

 

[Cut4fun]

Naw, I think it is just the owner creating the problem, hehe , using a 440 for 3" limbs at 1/2 throttle fouling the plug out. Jabjab

 

[bvaught]

Naw, I think it is just the owner creating the problem, hehe , using a 440 for 3" limbs at 1/2 throttle fouling the plug out. Jabjab

Yep.....thats probably what happened.