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New Stihl MS291 has me baffled

Started by WLC, October 01, 2016, 06:23:51 PM

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WLC

I bought a new MS291 back during the winter.  I used the new saw to cut up some blow down in the late winter and early spring.  I've probably run no more than 4 or 5 tanks of gas through it so far.  Week before last we basically had a hurricane blow through with high winds for a couple of days.  I had several trees in need of cutting with four of them threatening or on buildings with minor damage.  I pulled out the saw, gassed it up and started getting these trees down.  I had the first set of two on the ground and was limbing them up when in mid-cut the saw cut off.  Not out of gas, acted as if the switch had been simply flipped off.  Double checked everything all was well.  Tried to restart and nothing. Let it sit till completely cool and still nothing.  I plan on taking it to the shop my next trip to town but wondered if anyone here might have an idea.  Good thing I have a spare saw and was able to get them cut up and out of the way.
Woodmizer LT28
Branson 4wd tractor
Stihl chainsaws
Elbow grease.

Gearbox

A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

joe_indi

Yes, I second Gearbox. It can only be the coil, viz the speed limiter has (permanently limited the rpm). But, it could also be something as simple as a shorted spark plug

Ox

I would try a new spark plug first.  Sometimes they just fail like that.  If not that, it's the coil that went bad.
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

CTYank

Quote from: Ox on October 02, 2016, 11:20:31 AM
I would try a new spark plug first.  Sometimes they just fail like that.  If not that, it's the coil that went bad.

There's a phenomenon peculiar to 2-strokes known as "whiskering" where a small chunk of deposit in the chamber flakes off and attaches itself to the plug, across the gap. No mo spark. It can be small enough that it's hard to see on inspecting the plug. A credit card is a good gap-clearing tool. Good luck.
'72 blue Homelite 150
Echo 315, SRM-200DA
Poulan 2400, PP5020, PP4218
RedMax GZ4000, "Mac" 35 cc, Dolmar PS-6100
Husqy 576XP-AT
Tanaka 260 PF Polesaw, TBC-270PFD, ECS-3351B
Mix of mauls
Morso 7110

Ox

You are absolutely right.  I didn't think of a fouled plug.  It is also a very real possibility.  I should know better after turning wrenches most of my working life, it just slipped my mind.  ::)
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

WLC

Spark plug was the culprit.  I even pulled it and checked for spark before I took it to the shop.  New plug and she runs like new again.
Woodmizer LT28
Branson 4wd tractor
Stihl chainsaws
Elbow grease.

Ox

Good news!  Now get to work.  :D ;)
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

WLC

Quote from: Ox on November 06, 2016, 10:22:11 AM
Good news!  Now get to work.  :D ;)

Oh, I have been working.  That's the problem when you have two or more chainsaws.  One goes down, just reach for another. :D

Just glad it wasn't much wrong with it.  I should've known to try changing out the plug before taking it to the shop even though it had spark.
Woodmizer LT28
Branson 4wd tractor
Stihl chainsaws
Elbow grease.

Ox

I used to do the same thing, then the backup breaks and you're kicking yourself for not fixing the main saw.  As far as knowing better...we're all entitled to a brain fart now and again.  I'll bet you'll check the plug first thing next time something happens!
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

The Diesel

I had the exact same thing happen with my dads MS261CM but it was a 3-4 years old and had been used alot.  It was the coil.  Sounds like your should be under warranty.  I bought and replaced and it runs great now.

nitehawk55

A lot of owners forget that the saws have a lifetime coil warranty abd the shafts in the trimmers and brushcutters are lifetime as well .
I believe others have the same as well , pretty sure Echo does .
I AM NOT BRAND LOYAL !

WLC

Quote from: Ox on November 07, 2016, 09:53:18 AM
I used to do the same thing, then the backup breaks and you're kicking yourself for not fixing the main saw.  As far as knowing better...we're all entitled to a brain fart now and again.  I'll bet you'll check the plug first thing next time something happens!

Been there done that too.  You better believe I'll change the plug first thing next time.  Sorta baffling though.  I've got a 23 year old weedeater with LOTS of miles on it that still had the original plug up till about two or three years ago and a Stihl 026 I've had since 1990 with the original plug. Guess I've just had good luck with not having to change them so didn't really think it would be a problem with basically a new saw.
Woodmizer LT28
Branson 4wd tractor
Stihl chainsaws
Elbow grease.

Ox

I hear that loud and clear.  I have the same results here, with plugs I mean.  I think the newer plugs are being cheaply made along with everything else.  I hate it here.  I miss the older days when things seemed good.  I'm sure it was just that I was ignorant.
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

ladylake


Its really a shame what the present day management is doing to what were high quality company's, using a good name to sell low quality junk.  It took years for these company's to build up a good name and the present managers will ruin the name fast just to make more money now.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

joe_indi

I wouldnt say the saw quality has suffered because the spark plugs (NGK or Bosch) are getting fouled up. For some users the new 2Mix engine usually with Exhaust stratification coupled with electronically controlled ignition timing (retard and advance) with speed limiter could cause carbon buildup.
Usually from partial throttle running (carbs deliver richer mid range fuel:air )or full throttle without sufficient load (causes the speed limiter to cut off alternate sparks).
Both these cause the plug to foul up.
I saw this in the early days of the 461. The remedy is a coil swap, opening up the exhaust a bit and a re-tune (by ear) of the carb. Unconventional, but it works

Kbeitz

My Dad has a Stihl weed eater years ago that developed a knock.
I spent hours on the machine trying to find out what was causing the knock.
Dad said forget it. I need to cut weeds. So he put in ear plugs and went back to cutting.
I was disappointed that I could not fix it. I stood there watching it run.
It looked like the jug was moving in and out with the piston. So I stopped Dad to
tell him the jug was loose. The jug was part of the case so there was no way that
the jug was loose. I said ... But Dad I seen it moving. So we started it up so Dad could
see it... Something was moving. After investigating further we found the porcelain part
of the spark plug had come loose and was moving in and out with the piston.
How it could run that was was beyond me, but it ran just fine. The plug would move in and
out about 1/2" and hammer like a busted rod. One of those thing you gotta see to believe.
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

Ox

That's a good story, K.  And I believe every bit of it after seeing some of the stuff I've had to fix over these last 25 years.
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

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