Stihl MS261 Mystery

[mikegreen]

Hi. Jul.12.2022

I have a Stihl MS261 that I've owned since 2011 - not heavy use, I've cut about 75 cords with it, always in dry summer months. Saw visually appears to be in to top condition. There is no heating feature on this saw.

Last summer I could not start it so I installed a new Stihl module ($150 !!!) and spark plug . It worked fine for a couple of months. I then put the saw away for several months with fuel stabilizer run through it. As per a Stihl tech, I left the fuel in the carb. (Yes I know, the manual says to drain the fuel - not sure which is correct.)

Now, once again, it won't start after working fine about a year ago. I pulled the spark plug and noticed it was fairly dry. I stuck a finger in the spark plug hole and pulled the cord - my finger was slightly moist. Compression seems fine.

Then I checked for spark - there is NO spark. I checked the shutoff switch ground circuit, and it appears to be working fine. To be sure, I disconnected the wire going to the tab on the ignition module just to ensure that the primary winding was not shorting out to ground. Still NO spark. The spark plug gap is .025".

I checked the magnets on the flywheel - no discolorization. Fairly strong pull on the "N" magnet to my screwdriver. I tried a different spark plug to no avail. The ignition module bolts are tight and the flywheel gap is .007 (.178mm).


The resistance from the spark plug boot to the ignition module ground is 2 Kohms as per spec.

Now I haven't a clue as to what to do. How could the ignition module go bad after sitting for a year????

Any thoughts or advice would be greatly appreciated.

Thanks in advance for any input,
M...

 

[Duane(Pa)]

Hi. Jul.12.2022

I have a Stihl MS261 that I've owned since 2011 - not heavy use, I've cut about 75 cords with it, always in dry summer months. Saw visually appears to be in to top condition. There is no heating feature on this saw.

Last summer I could not start it so I installed a new Stihl module ($150 !!!) and spark plug . It worked fine for a couple of months. I then put the saw away for several months with fuel stabilizer run through it. As per a Stihl tech, I left the fuel in the carb. (Yes I know, the manual says to drain the fuel - not sure which is correct.)

Now, once again, it won't start after working fine about a year ago. I pulled the spark plug and noticed it was fairly dry. I stuck a finger in the spark plug hole and pulled the cord - my finger was slightly moist. Compression seems fine.

Then I checked for spark - there is NO spark. I checked the shutoff switch ground circuit, and it appears to be working fine. To be sure, I disconnected the wire going to the tab on the ignition module just to ensure that the primary winding was not shorting out to ground. Still NO spark. The spark plug gap is .025".

I checked the magnets on the flywheel - no discolorization. Fairly strong pull on the "N" magnet to my screwdriver. I tried a different spark plug to no avail. The ignition module bolts are tight and the flywheel gap is .007 (.178mm).


The resistance from the spark plug boot to the ignition module ground is 2 Kohms as per spec.

Now I haven't a clue as to what to do. How could the ignition module go bad after sitting for a year????

Any thoughts or advice would be greatly appreciated.

Thanks in advance for any input,
M...

@SOS Ridgerider can you move this to chainsaw forum for better prospects?

 

[huskihl]

Pull it over faster and check for spark

 

[blades]

loosen and re-tighten all electrical connections, might just be some oxidation somewhere. I do not know if there is a way to check the module its self. also check that the kill switch wiring is not shorted out from rubbing on or pinched by something . That has shown up more than a few times.

 

[r7000]

How could the ignition module go bad after sitting for a year?

Bought a northern tool 5kw generator few years back, had a honda engine. Out of the box it started, shut it off, moved it, tried to start a few days later. Would not, bad coil. Dunno. It was not a traditional simple coil, it was a fancy one with built in timing retard for pull starting the engine, and cost me $80 for a mail order replacement (fortunately which hasn't failed after numerous hours of use since).

only other thing i can think of to mention is don't overlook not grounding your spark plug well enough when it's removed from the cylinder (when trying to observe spark). It can be a pita with just one person rigging it up... short of holding the spark plug lead and defibrillating yourself. If your saw has one of those kind of coils, then unfortunately it happens is all i can say.

 

[066 redeye]

Ensure no corrosion under coil where it bolts to the case.

 

[SOS Ridgerider]

@SOS Ridgerider can you move this to chainsaw forum for better prospects?

It's been moved. Wow, I'm slow...

 

[Mastermind]

Ensure no corrosion under coil where it bolts to the case.

Good advice.