Sudden Idling Issues After Cold Weather

[Bendroctanus]

I might be lazy for bot wanting to thresh through the archives.

Had it happen on an MS441 Magnum and an MS660 Magnum. Both have had the cylinder replaced in recent years (not sure if that’s pertinent). Haven’t changed fuel or anything. I feel as though I had them tuned well. The 441 might be a leak issue as it is losing compression or making a funny noise after a while. Thought replacing the jug would fix it. It ran all summer without issues. The 660 was also running fine, (like a badger as my Saw-Fathah used to say), and now idles high and then dies after awhile. Seems to be related to the cold snaps we’ve been having (Central Illinois) but not entirely sure.

Penny for anybody’s thoughts.

 

[Brando CalPankian]

Non-ethanol (sorry, first place to start).

 

[Bendroctanus]

No, I refuse to run any ethanol. Made that mistake a long time ago. I’ve been using alkalyte for a while, VP and Aspen.

 

[evo]

Define temps? Maybe flip the cold air intake thingy?
Other than that a carb tune and failing that I’d start looking at old/bad gas issues

 

[Bendroctanus]

Well mostly staying below freezing but we had a some snaps of single digits and negative wind chill. I didn’t necessarily run them too much during but the saws live in the saw box. It does seem to be acting like the tuning is out of whack or bad gas but alkalyte fuel has a shelf life of one to two years. I’ve never had a problem with it sitting for awhile. It’s just weird, everything was running fine before December and now I have two saws running weird. I tried adjusting the 441 but no dice.

 

[Bart_]

Maybe something sealing less well in the cold? Older harder crank seals? vent/pressure line etc.. hardened carb diaphram harder in cold?

My well used 200T runs different in the cold, actually ms260 too. I switched crank seals on a br400 or 420 and it was like I put a new carb on it.

 

[flyingmosstreen]

Agreed with above. Fuel tank vent would be another spot to check?

 

[flushcut]

Check for an air leak, carb boot is a good place to start.

Saw-Fathah: I like that!

 

[Bendroctanus]

Ok, figured it out. The main problem….
Was yours truly.

Haha, but in all seriousness it feels like a silly mistake. @Bart_ I think you were the closest. Thank you, and everyone for chiming in.

The common denominators were had manual carburetors, and that I rebuilt them both this last year. After messing with the carbs with no luck, it finally occurred to me to check the cylinder screws. I put it off because I thought there was no way that they had come undone. But, my theory is, that after breaking in this last year and meeting the frigid midwest cold for the first time, they loosened just enough to work themselves out. All the screws were loose, and both saws lost one screw altogether. Tightened them down good, and they fired right up. A very roundabout way to get them new spark plugs. I’m thinking I may need to come back around and hit them with some loctite. But, a good one to remember.

Also, checking compression on the top end may not tell you this is the problem. I checked compression on the 660 before I thought to check the screws, but it seemed to hold pressure just fine. It makes sense since the spark plug hole is above the seal.

Anyway, learn from these fine gents and an idiot like me. I will boldly go forward making dumb mistakes if only so others can avoid my boneheaded moves.

Thanks again!