Stihl MS261 mtronic

[BlueMax]

MS 261 stalls when taken off choke. Spark plug checked and clean, new white solenoid kit installed with new fuel filter. New air filter. Carb taken off and soaked in carb cleaner overnight.

instructions followed for resetting by idling for 90 seconds and then shut down. 

Starts fine and runs on choke but as soon as choke removed it stalls. With cover removed and air filter removed I can see that if I slowly release the choke it’s ok until about half way and then just stalls. Can be run at full throttle sometimes, without choke, but as soon as throttle down it stalls. 
This is frustrating me, any ideas what could be causing this as a new ignition pack is a costly way to check.

[pleasant]

Ideally the carb should be ultrasonically cleaned out. Leaving it overnight in carb cleaner is A. quite corrosive and B. does nothing to remove blockages in ports, jets etc, which is if you do have carb issues is generally where your problems are.

[spudulike]

Have you checked the clutch drum bearing as this model is notorious for killing them. Other than that, make sure the clutch springs are OK but if the clutch drum bearing is knackered, make sure you check the oiler pinion arm is in good shape. 

The Mtronic ones were far better than the normal carb ones in regards to clutch bearing issues.

Edited March 25, 2023 by spudulike

[BlueMax]

I have removed the bar for safety to work on it. So the latest is that it start quite easily on choke and will run forever. If I grab the throttle and hold it WOT, with choke off, it will scream for as long as I hold the throttle WO. I can reduce the revs slowly to about half and it’s ok but then as I slowly reduce revs more it start to sound a bit rough and if I go to idle it stalls.if I go from choke straight to idle it stalls. It feels like it might be starved of fuel at idle. If it had an idle jet I would rich it up, but it doesn’t so can’t. As the solenoid is new could the mtronic chip be duff? Fuel is fresh and 50:1.

[Stubby]

Just now, BlueMax said:

I have removed the bar for safety to work on it. So the latest is that it start quite easily on choke and will run forever. If I grab the throttle and hold it WOT, with choke off, it will scream for as long as I hold the throttle WO. I can reduce the revs slowly to about half and it’s ok but then as I slowly reduce revs more it start to sound a bit rough and if I go to idle it stalls.if I go from choke straight to idle it stalls. It feels like it might be starved of fuel at idle. If it had an idle jet I would rich it up, but it doesn’t so can’t. As the solenoid is new could the mtronic chip be duff? Fuel is fresh and 50:1.

And God hates you 😀

[BlueMax]

Yup😬…and I bet if I buy a new carb I will afterwards discover a previously unknown break in the solonoid wire or something! Pretty sure it’s fuel starvation at idle.

[Stubby]

1 hour ago, jonconner said:

most common carburetor problems is a clogged carburetor, which can prevent fuel from reaching the engine.To fix this, you need to remove the carburetor and clean it thoroughly

Including the small gauze filter . Better still an ultrasonic cleaner . 

[pleasant]

ompression and leakdown tests then

[adw]

Not into Stihl machines, however where is the impulse taken from ? and has it come adrift or blocked? just a thought.

[Trailoftears]

Not sure if this helps you but there's different procedures for recalibrating/resetting mtronic versions/software vers.Is yours a v.3 for instance?