Stihl 261CM suddenly stall-prone

[fc1]

I've had my Stihl 261C for about 3.5 years and operator-errors aside it's always been totally appliance-like in its function. Kept it sharp and in fluids and it worked great, consistently.
Until recently...
Now from cold it will fire and run in "Start" just fine, but unless I'm careful to run it (cut) immediately off "Start" it will usually stall and refuse to refire for an extended period.
Spark arrestor is clean. Air filter is original but not visibly dirty in a way that looks to have an impact. I wire-brushed and regapped the plug (and confirmed spark).
I got fresh gas and made fresh premix. All of which made zero difference.
I know both the coil and fuel solenoids have caused problems; does my issue sound related? Time for dealer visit? Should still be under warranty...

 

[xyz123]

WAG. Seen this on others. Sounds like dirty solenoid.

They have a updated ones and fuel filter for alot of stihl's now.

Only sure way to know is pay the piper to hook it up at dealer.
Or take the chance and replace the 2 parts yourself and save the $100 a hour they going to charge ya. But if not it cost ya anyways.

 

[dodge man]

I know the spark plug looked ok but I’d stick a new on in it. I had a spark plug fail and the saw acted like you described. That’s probably not the issue but cheap to replace.

 

[xyz123]

Yes do that first put new plug it it before jumping further. I have had new plugs from ngk even be bad right out of the box. So just make sure you use a known good plug.

Here is what the new fuel filter looks like. If you have a white one it lets double the fine size by.

 

[Dan Hunter]

I vote bad plug as well. 2-strokes are firing twice as often and run at what would be crazy RPMs in a 4-stroke. They just don't last as long.

Just last week, my leaf blower began to struggle. It'd start but not want to build RPMs. The plug had great color but was old. A fresh plug solved it.

 

[ericm979]

New plug and the correct fuel filter (Mtronic needs a better one than the usual one for carbs).

Then try the Mtronic reset procedure. It should be in the manual. There's two different ones depending on the generation of the Mtronic.

 

[dodge man]

The plug I had go bad the center electrode could be pulled out it was so loose, that sucker is long.

 

[fc1]

Y'all are awesome. I have to admit I headed to AutoZone this am with the idea that while it would be *nice* if the plug fixed it, but...

The improvement in the saw was so obvious and immediate that I swapped plug in my 2-stroke Kombi as well. What do you know- the start/idle/restart behavior on that improved too!

Sincere appreciation for the input.

 

[Hay Dude]

My 1 year old heavily used 261C began the same issue yesterday. It ran fine, then it would start and idle, but as soon as you’d try to tach it up, it would stall.

I dumped out the fuel tank and tried some newer fuel from another fuel jug and it ran again.

However the other saws ran fine on the previous fuel so I’m suspicious its something else.

 

[fc1]

Spark plug worked for me!

 

[stevem5215]

I dump the gas out of the saw if it's been there a year or so. Kill some weeks or something with it. Just not worth messing with bad gas in a 2 stroke as it can damage the engine with this crummy ethanol gas phase separation problem. New gas mix is better and more consistent operation.

 

[dodge man]

I’m glad it was an easy fix and you started with cheap stuff. I can’t recall how long ago it was on this forum but someone had a problem with a small engine. I said the same thing I did in this thread, “it’s probably not the spark plug but…..”. This went on for a few days with all sorts of advice. I finally asked if he put a spark plug in. He finally did and you guessed it that fixed it.

I’ve had my fair share of small engines running funny and I think I’ve only once had a spark plug be the problem but it’s also cheap to replace.

 

[RandyT]

I’m glad it was an easy fix and you started with cheap stuff. I can’t recall how long ago it was on this forum but someone had a problem with a small engine. I said the same thing I did in this thread, “it’s probably not the spark plug but…..”. This went on for a few days with all sorts of advice. I finally asked if he put a spark plug in. He finally did and you guessed it that fixed it.

I’ve had my fair share of small engines running funny and I think I’ve only once had a spark plug be the problem but it’s also cheap to replace.

Rule #1 of small engines, Never trust the spark plug.

 

[stevem5215]

My dad helped a guy tear down lawn mowers that had "died". The guy who showed him the ropes mentioned that he should save all the spark plugs in them. And the reason is that it's the last thing everyone tries before junking the mower. The guy had a giant bucket of brand new spark plugs he'd give away to people who needed a new plug. Recycling at it's finest lol

 

[dadohead]

I dump the gas out of the saw if it's been there a year or so. Kill some weeks or something with it. Just not worth messing with bad gas in a 2 stroke as it can damage the engine with this crummy ethanol gas phase separation problem. New gas mix is better and more consistent operation.

Yeah, a boatload of issues can be avoided using fresh 91 octane NO ETHANOL fuel in your small engines.

 

[gsganzer]

I had a Husky 550XP that also suffered the bad plug plague. It would start and run fine one minute, minutes later you'd go to start it and nothing. It was frustrating. New plug was all it took.

 

[Hay Dude]

I just went through a bout of poor running with my 261C and as stevem5215 said, just dump out the gas and get new fresh fuel. My 500i seems less susceptible to bad fuel, but it might have a newer, hotter spark plug, too.
Mine would start and idle, but then stall as soon you touch the throttle.
Dumped out fuel and went to fresher fuel. Ran perfectly

I think fuel with any ethanol in it goes stale in a matter of weeks now. I mix 5G when I’m on a big sawing/clearing job, but always have in mind to use it all. If it sits more than 3-4 weeks, it’s usually going to give me problems.

Been experimenting with StaBil in my tanks a little bit to see if it’ll help and it really seems to help.
The key is to keep running your saws.