MS260 Won't Start - What to Look For?

[Philbert]

(No Husqvarna jokes please!)

Was trying to help a friend whose STIHL MS260 would not start. Saw looked to generally be in good condition. Said it was running fine 'a few months ago'. Thought that I could help, being a 'saw guy'. ***All this was in the field***

SPARK, AIR, FUEL, and COMPRESSION (right?). Here is what I did:

- COMPRESSION: felt normal when pulling on the starter rope, and saw was reported to be running fine when last used.

- AIR: removed and inspected the air filter: used but pretty clean. Spark arrestor screen was clean.

- SPARK: checked for spark from the coil with an automotive type spark tester. Plug looked fine, but replaced it anyway, just in case. Checked the plug gap, and made sure that the 'kill switch' was not grounding out.

- FUEL: don't know how long fuel might have been left in the tank during some earlier period, but tank was mostly empty. Drained out the remaining fuel, replaced the fuel filter, and filled the tank half way with Tru-Fuel (canned, pre-mix, alcohol free stuff). Placed some fuel on the air filter with an eye dropper. Took the carb adjustment screws back to the starting points in the owner's manual. All these things done while pulling on the starter cord 20+ times after each thing tried. Tried some flooded saw starting techniques as well, even though fuel was never smelled. Never got a 'burp' or a 'bark'.

Again, this was in the field and not a shop setting. They are probably going to take it to the dealer. I am assuming something with the carb. Anything else someone could try, or look for in the field?

Thanks.

Philbert

 

[Simondo]

Assuming you have ..seen a spark at the plug.. by holding it against the cylinder top then it is "probably " pointing towards the fuel system .
A few pointers....
Fuel line on 026 is tightly bent and twisted (as i know well from a 024 issue !! ) on rout to carb and in tank...check out as the air filter will push on it when you install it to.
Impulse line ...is it connected and not holed .... is the hole to the metering side of the carb plugged with crap.
Choke flap in the filter...is it "actually " coming on .
Identify if the innards of the carb are ok and fuel is getting in there ..if not ..you know its ether not being pulled through or there is something stopping it.
Hope something shows or these suggestions trigger you finding the problem.
Simon

 

[panteliss]

Check the carb with presure - vacuum pump
check the impulse line and the intake boot
check the flywheel key if is in good contition and in right place

good luck

 

[Brian Simonseth]

Don't laugh

I can't do much any more but I had a friend come over with a ms360 and he said about the same thing about his saw; I dumped out the old fuel put fresh fuel in and watching how many turns it took turn in each the "H" and "L" screws on the carb and the backed them both out to were they were handed him the saw it started on about the fifth pull he gave it

Learned that from a Fireman

 

[paragonbuilder]

If you can't get a pop with fuel down the carb throat, I'd pull the filter, then I'd say spark or timing key like pantelis said.


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[trooney]

Like paragonbuilder said, put fuel down the carb throat. If you get a pop, its a fuel issue. If not, then I'd check spark, P&V, and even pressure test the carb. Since your not smelling fuel when it should be flooded its hopefully something gunked up in the carb not letting fuel get by, carb needs a rebuild (pull the diaphram cover and see how the gaskets are) or the fuel line/fuel fliter. I've had my share of 026's that when you pull the tops of the carb its all gunked up with wood dust.

 

[panteliss]

Its easy

if you pull the rope and the saw start to smell of fuel is two reasons

1 ) the needle in the carb have problem
2) the flywheel have moved , key break , or something

 

[Philbert]

Thanks guys.

The things I tried (first post) are my 'field diagnosis' techniques. Things like pulling a carb, pressure testing, etc., are more like 'shop techniques' for me, although, I understand that some can still be done in the field. Always looking to learn new things. Since it had a good spark, but the saw would not fire with fuel dripped onto the air filter, it makes me suspect that I will learn something new from this saw.

If it was my saw, I would now pull the carb, try a rebuild, replace lines, etc., and try again. Or even try swapping carbs. Will see what the STIHL dealer says.

Makes me wish for a simple 'flooded' saw.

Philbert

 

[paragonbuilder]

Thanks guys.

The things I tried (first post) are my 'field diagnosis' techniques. Things like pulling a carb, pressure testing, etc., are more like 'shop techniques' for me, although, I understand that some can still be done in the field. Always looking to learn new things. Since it had a good spark, but the saw would not fire with fuel dripped onto the air filter, it makes me suspect that I will learn something new from this saw.

If it was my saw, I would now pull the carb, try a rebuild, replace lines, etc., and try again. Or even try swapping carbs. Will see what the STIHL dealer says.

Makes me wish for a simple 'flooded' saw.

Philbert

I would try more than a few drops on the filter. Some saws need a good quick shot right down the carb. If you are using a dropper I'd do a full one, and give her some yanks.


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[drf256]

Sure sounds like an ignition timing problem. My first and only one drove me insane.

I've found priming through the carb throat very forgiving. At least for me, it's been tough to flood a saw. I use a trickle right from my gas tank of mix. Likely 2-5cc.

The air filter on an 026 can make anyone insane. New ones that are flocked, OEM included, can flow very little air and make the saws pigs. But this wouldn't be a starting issue.

I'd be pulling the flywheel as your next step.

 

[paragonbuilder]

Philbert, did you figure this out?


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[Philbert]

Not my saw. Had one chance to diagnose/fix it. Owner was going to take it to STIHL dealer and get back to me. I will post what they find if I find out.

Thanks for all the input.

Philbert

 

[paragonbuilder]

Not my saw. Had one chance to diagnose/fix it. Owner was going to take it to STIHL dealer and get back to me. I will post what they find if I find out.

Thanks for all the input.

Philbert

Great. It would be nice to know.


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[MustangMike]

So, what happened??? Sounds to me like the flywheel spun, or the coil is going bad. The primary winding can give a spark even when the secondary winding is bad.

 

[a. palmer jr.]

My troubleshooting technique is a little different: I put fuel directly into the cylinder through the spark plug hole, then if it hits you've eliminated the ignition ,timing (flywheel key) and compression and can go to the fuel system.

 

[drf256]

My troubleshooting technique is a little different: I put fuel directly into the cylinder through the spark plug hole, then if it hits you've eliminated the ignition ,timing (flywheel key) and compression and can go to the fuel system.

How does that eliminate the flywheel key?

 

[Philbert]

I put fuel directly into the cylinder through the spark plug hole, . . .

How much? How do you prevent flooding?

Thanks!

Philbert

 

[paragonbuilder]

How does that eliminate the flywheel key?

If it pops, it's got spark at the right time. I don't see how this is different than putting some down the carb though...


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[paragonbuilder]

How much? How do you prevent flooding?

Thanks!

Philbert

If it's too much it'll just blow out the exhaust. Just take an extra pull or two.


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[huskihl]

If it pops, it's got spark at the right time.

Not necessarily. Especially if it's just a pop. I had an 084 with 2 key slots in the crank. It would pop every time I pulled it. But all it did was pop. I moved the key to the other slot and it ran fine, which was probably 30° off