Cannot start MS260

[deanbrown]

Hi!

Can anyone help me on what to try next here? My Stihl MS260 was not used for around a year or two. Now I cannot start it. I'm literally almost fainting with exhaustion pulling the cord after trying different things. Here's what I've tried so far. I never ever get any hint of combustion, it is as if it's completely dead:

1. Removed carb, dismantled, left if carb cleaner for a day, blown out all the holes.
2. Cleaned air filter - opened it in half and blew out from the inside.
3. Put in TruFuel 1:50 fuel from brand new bottle.
4. Tried spraying carb cleaner through the carb and starting.
5. Tried TruFuel through the spark plug hold - a dropper full, and then 3 droppers.
6. New spark plug. When I pull the plug and ground it, and pull the cord, I do see a spark BUT ONLY when I pull fast. When I pull at what I consider low to moderate levels I don't see anything.
7. Checked the spark arrestor - the fine mesh is completely clean.
8. Checked that fuel is being pulled up - I can see it at the top of the tube when I pull off the black rubber tube that goes into the carb. Fuel filter looks completely clean.

I've tried holding the carb on full speed mode (put a bungee on the handle to hold it open) and pulling dozens of times with it in run position. Nothing. Even when I have put fuel directly into the cylinder.

My guess is that the ignition system is weak and there's no spark inside the cylinder, despite me seeing sparks with the plug pulled and I pull the starter fast.

I'd truly like to fix this myself and understand what the problem(s) are, as I have another two saws that need similar TLC.

 

[2StrokeFondler]

Is your spark plug wet after you tried starting it?
Did you gap the coil properly?
Is your plug wire 100% intact?
Did you get the correct replacement plug?
I would re-assemble everything and make sure your cylinder is dry. Now, don't spray carb cleaner into the inlet. Just give it a teaspoon of fuel and try to start it on fast idle.

 

[deanbrown]

Hi 2Stroke,

Spark plug was a little wet with fuel. Is that good or bad?
The gap on the coil is 0.004" (4 thou). Hardly the 'business card' thickness I've seen on YT.
Plug wires intact? Umm, I've not done anything except inspect, but can't see anything wrong.
Plug is correct according to the manual. Gap is correctly set.

I tried your last point already. Nothing, completely dead.

 

[ZeroJunk]

Find somebody to help you. Let them hold the throttle trigger wide open. No choke. Pull it maybe 20 or 30 times. If it does not start the chances are it does not have enough compression to run.

 

[2StrokeFondler]

Hi 2Stroke,

Spark plug was a little wet with fuel. Is that good or bad?

Means your carb is probably working.
Not a single pop on a dry machine with a teaspoon of fresh fuel points to an ignition problem, IMHO.
Does your muffler have a spark screen? Is it free?
If you're sure you have good compression, I'd change the ignition module for a test. Is one of your other saws a Stihl with a matching ignition?

 

[2StrokeFondler]

Find somebody to help you. Let them hold the throttle trigger wide open. No choke. Pull it maybe 20 or 30 times. If it does not start the chances are it does not have enough compression to run.

I use a piece of tape for that. Just have to remember to shut the thing off the second it pops.

 

[deanbrown]

I tried it again - put in 4cc TruFuel directly through the wide open carb. With my wife holding it down with a foot, the switch on the first click, and trigger bungeed open, I pulled 50 times. Then after a break another 40 times. Nothing, not a single pop.

I can get sparks of up to 8mm with a spark tester. But I do have to pull really fast to get anything. Anything less than 'magnificent' and there's no spark at all.

Saw has maybe a dozen or two hours on it max.

Does anyone have the specs for the coil/wheel gap?

 

[ZeroJunk]

I tried it again - put in 4cc TruFuel directly through the wide open carb. With my wife holding it down with a foot, the switch on the first click, and trigger bungeed open, I pulled 50 times. Then after a break another 40 times. Nothing, not a single pop.

I can get sparks of up to 8mm with a spark tester. But I do have to pull really fast to get anything. Anything less than 'magnificent' and there's no spark at all.

Saw has maybe a dozen or two hours on it max.

Does anyone have the specs for the coil/wheel gap?

Spark, fuel, compression.... That is it. Unless, your flywheel has spun out of time somehow and it sparks at the wrong time.

You have lost compression somehow or the other most likely.

 

[cookies]

remove the spark plug and use compressed air to dry the piston and cylinder of gasoline. Dump the canned fuel and use freshly mixed fuel. Start the saw without choke on but set to high idle.

 

[lone wolf]

If it ran when you put it away, chances are the carb is bad. I suspect it could now be flooding after working on it, like someone mentioned dry it out and clean the plug then try a little more fuel if it don't pop after 10 pulls stop trying. Pull the muffler and look for scoring on the piston also. We will take it from here.

 

[deanbrown]

I've tried (1) carb cleaner sprayed through the carb, (2) gas through the carb, and (3) different amounts of gas directly through the spark plug hole. Never once has it 'caught'. Can you sanity check this - each time I clamp the throttle down to full speed, with the switch on the first position - regular running position. No air filter. Carb looks wide open. Then pull 20-30 times as fast as possible.

 

[lone wolf]

I've tried (1) carb cleaner sprayed through the carb, (2) gas through the carb, and (3) different amounts of gas directly through the spark plug hole. Never once has it 'caught'. Can you sanity check this - each time I clamp the throttle down to full speed, with the switch on the first position - regular running position. No air filter. Carb looks wide open. Then pull 20-30 times as fast as possible.

Pull the muffler and look at the piston and post a picture of it.

 

[stihltech]

Time to quit just pulling and diagnose. Lots of good info so far. Until you have time to get into it, get that muffler off as stated before. Time to see if there is anything to work with.
Leave the sparkplug out and the muffler off. Let it sit. Also turn the saw upside down and pull to see if fuel comes out plug hole and exhaust.
DO NOT put any more fuel in it! It needs to dry out to start over.
Sounds like an extremely flooded unit. Carb cleaner will not fire with that much fuel.

 

[Sidecarflip]

Why not just take it to your local dealer and pay to have it fixed? Sounds to me like you are just shooting blanks.

 

[ZeroJunk]

I tried it again - put in 4cc TruFuel directly through the wide open carb. With my wife holding it down with a foot, the switch on the first click, and trigger bungeed open, I pulled 50 times. Then after a break another 40 times. Nothing, not a single pop.

I can get sparks of up to 8mm with a spark tester. But I do have to pull really fast to get anything. Anything less than 'magnificent' and there's no spark at all.

Saw has maybe a dozen or two hours on it max.

Does anyone have the specs for the coil/wheel gap?

The whole point of that exercise was getting fuel out of it, not putting more in it.

 

[deanbrown]

Pull the muffler and look at the piston and post a picture of it.

 

[lone wolf]

Bingo it's destroyed! Straight gassed, I am fairly positive. Who did you lend it too?

 

[user 188535]

Hi 2Stroke,

Spark plug was a little wet with fuel. Is that good or bad?
The gap on the coil is 0.004" (4 thou). Hardly the 'business card' thickness I've seen on YT.
Plug wires intact? Umm, I've not done anything except inspect, but can't see anything wrong.
Plug is correct according to the manual. Gap is correctly set.

I tried your last point already. Nothing, completely dead.

Business card trick worked for me.

 

[lone wolf]

OP you need to pull that cylinder off, and I bet you are going to need a new Cylinder and piston don't buy cheap China knock offs buy OEM STIHL.

 

[Sidecarflip]

Assuredly straight gassed, It ain't gonna ever start no matter how much you pull the rip cord. If you never loaned it out then you did it yourself. Piston looks like 5 miles of bad road. Just venturing an educated guess... You need to take it to an authorized Stihl dealer and have them rebuild it as it kind of apparent you lack the technical expertise to do that. Not trying to be insulting, just stating the obvious.

I'm surprised it even turned over with the amount of scoring on that piston.