440 idle?

[stihl 440]

I've been tuning my 440's idle, and now when it gets hot it'll idle fast the go reallll slow, and if I let it go it will stall. And along with the idle problem it will now take (sometimes) 2-3 pulls to restart after about 3/4 of a tank of cutting. And normally (right before it started acting up before I messed with it) it was a one pull start if warm saw. I've got it to quit surging with the L screw. And I can get it to idle perfect if cold, but once it warms up it changes to the above description. Any tips? :hmm3grin2orange:

 

[Lakeside53]

1) Tank vent
2) Carb inlet needle, or stiff metering diaphragm
3) Crank seals


Check the carb. Then do a pressure test to eliminate or validate the seals.

 

[stihl 440]

saw shop

1) Tank vent
2) Carb inlet needle, or stiff metering diaphtragm
3) Crank seals


Check the carb. Then do a pressure test to eliminate or validate the seals.

Looks like a trip to the saw shop, eh? Thanks lakeside, I had a bad feeling it probably was a tank vent or someting with the carb.

 

[Lakeside53]

Shop????

HUH? surely there's enough knowledge to be used from AS to remove the shop from the loop?

 

[stihl 440]

pressure

HUH? surely there's enough knowledge to be used from AS to remove the shop from the loop?

Well, how do I pressure test it without going to the shop? What are the symtoms of a bad tank vent or carb inlet needle or diafram?

 

[tek9tim]

I've had this kind of problem with all of the 440s with compression releases I've ever run. (not saying anything about the compression release, just describing age) BUT, that's only about 4-5 saws. All did it pretty much from the start, I could never get them to stay well tuned, I just always had a screwdriver. Some were stock, the rest had muffler mods. Seemed like the muffler modded ones did a little better. Still had to be tweaked every now and again.

Edit to add: Easy way to check the tank vent is to crack the gas cap after you have trouble and listen for air sucking into the tank.

 

[stihl 440]

thanks!

I've had this kind of problem with all of the 440s with compression releases I've ever run. (not saying anything about the compression release, just describing age) BUT, that's only about 4-5 saws. All did it pretty much from the start, I could never get them to stay well tuned, I just always had a screwdriver. Some were stock, the rest had muffler mods. Seemed like the muffler modded ones did a little better. Still had to be tweaked every now and again.

Edit to add: Easy way to check the tank vent is to crack the gas cap after you have trouble and listen for air sucking into the tank.

Thanks tek, I'll do that!

 

[stihl 440]

fixed

She's fixed, L screw was too rich, starving it of air once hot. Here's how I fixed it, I ran 3/4 tank out of it, and it started not wanting to idle and taking more than one pull to start, so I got out the screwdriver, I leaned out the L screw until it would idle steadly, without surging. Then I did the start test. I shut it off, one pull away she went. That's how it was for the rest of the day. Thanks for the help though. :rockn: