Stihl MS 261 C-M challenge

[PlinkerMan]

I’m repairing a 261 m-tronic version. I could use some guidance if anyone can help... the problem is I can get the saw to run, but it runs rough and will only stay on in “start” position or if throttle is pressed. After this, it will only run momentarily and then it struggles / dies. Then it floods and Repeat. I was able to complete the “90 second reset” but then it again flooded and still won’t start.

So, here is some background information as to items tested so far:

Compression is 148-150

Tested spark plug, getting spark.

Pressure and Vacuum tested both tank, and crank case, no leaks.

Fuel filter is clean and not clogged.

I have another saw, same model, and I’ve been changing parts to try and troubleshoot issues. The other saw runs perfect and has no issues.

Changed the carbs, trouble saw still will not start. Other saw starts fine.

Changed fly wheel and ignition coil (not wires),
trouble saw still will not start. Other saw starts fine.

Anybody have suggestions for next steps or what could be wrong?

 

[Ryan'smilling]

Spark screen?

 

[PlinkerMan]

Spark screen?

Thank you for the suggestion. Checked the screen and it is clean...

 

[tmclarke11]

This sounds very similar to what I experienced with my ms261m earlier today. I don’t want to hijack your thread, so I will watch for responses and hope to get some clarity on a path forward in resolving my saw’s performance through members’ feedback. Mine is nearly a brand new saw with less than four tanks through it and surely under 8 hours of work so far. Can you point me toward a thread describing the 90 second reset process?


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[PlinkerMan]

This sounds very similar to what I experienced with my ms261m earlier today. I don’t want to hijack your thread, so I will watch for responses and hope to get some clarity on a path forward in resolving my saw’s performance through members’ feedback. Mine is nearly a brand new saw with less than four tanks through it and surely under 8 hours of work so far. Can you point me toward a thread describing the 90 second reset process?


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PM sent

 

[cuinrearview]

Sounds like a bad fuel solenoid.

 

[PlinkerMan]

Forgot to add that. I replaced the solenoid with new one also and it didn’t help my issue

 

[cuinrearview]

What happens if you put the coil from the good saw on the bad saw?

Sounds like it's time to belly up to the dealer teet and get it hooked up to the magical computer.

 

[PlinkerMan]

I changed the coil from the good saw/bad saw where it still resides. The good saw still runs and bad saw still doesn’t. Same with the carb

 

[super3]

Changed fly wheel and ignition coil (not wires),
trouble saw still will not start. Other saw starts fine.

That part there in red, did you try the plug?

 

[cuinrearview]

I've also heard those dinky wires are easily damaged.

 

[SteveSr]

I changed the coil from the good saw/bad saw where it still resides. The good saw still runs and bad saw still doesn’t. Same with the carb

On this saw the fuel solenoid is controlled by the ignition module so you should probably try moving BOTH from the good saw to the bad saw to see what happens.

 

[Rockjock]

This sounds very similar to what I experienced with my ms261m earlier today. I don’t want to hijack your thread, so I will watch for responses and hope to get some clarity on a path forward in resolving my saw’s performance through members’ feedback. Mine is nearly a brand new saw with less than four tanks through it and surely under 8 hours of work so far. Can you point me toward a thread describing the 90 second reset process?


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If it is less than a year old take it in for service, the solenoid is it the upgraded one?

 

[Derrick Sawyer]

What else would have a fuel delivery effect? Is there an impulse line?

 

[huskihl]

Try it without the air filter

 

[PlinkerMan]

That part there in red, did you try the plug?

No, have not changed the wiring from the good saw. Pretty certain it’s not the wiring but may come back to this.

 

[PlinkerMan]

On this saw the fuel solenoid is controlled by the ignition module so you should probably try moving BOTH from the good saw to the bad saw to see what happens.

I did swap both of these items from the good saw. No luck here

 

[PlinkerMan]

If it is less than a year old take it in for service, the solenoid is it the upgraded one?

Unfortunately it’s >1 year. It has manufactured date of 10/14

 

[PlinkerMan]

What else would have a fuel delivery effect? Is there an impulse line?

Yes, impulse line was checked with pressure/vac test. Seems good

 

[PlinkerMan]

Update: still no answer on this. Talked with local shop today as well as Rep from Stihl Tech team. Verbal troubleshooting with each of them only left me more frustrated as there was nothing conclusive and only confirmation as to the testing I’ve already completed.

Tomorrow the saw will go visit a friend of mine, a ways away from home, who is a keen mechanic. Hoping to have some answers soon..... to be continued