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Stihl 051 AV no power/won't idle

WillG

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A few weeks ago I was cutting some big red oak with my 051AV, was running excellent and cutting nicely. Was burying the bar on all cuts, when I finished cutting it lost power and wouldn't idle. Seemed to be very hot. Got home and let it cool, still wouldn't idle and had no power/wouldn't reach full RPM. Checked compression is 140 psi, plug was cardboard brown. Pulled carb off and apart and was nice and clean inside. Was pulling 9500 rpm and max is 10000. Has spark and is blue. Any ideas on what happened?
 
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KYsawman

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Did you check the exhaust side of the piston for scoring? Seals on old saws can leak and score the piston in a hurry.
 

WillG

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I will have to pull the muffler off and have a look. Will report back once I check.
 

WillG

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Did you check the exhaust side of the piston for scoring? Seals on old saws can leak and score the piston in a hurry.
Piston is absolutely perfect. I'm suspecting an ignition problem since the way it runs is it seems like you are turning the stop switch on and off really quickly.
 

AVB

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Could be a broken high tension lead (plug wire). These coils that uses the push in plug terminals are known to break the wire leading to loose contacts and intermittent spark.
 

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This a very good place to start. Not hard replacement and gives you an answer quickly.
Could be a broken high tension lead (plug wire). These coils that uses the push in plug terminals are known to break the wire leading to loose contacts and intermittent spark.
I got an 051 in pieces and thought do I need to put this together. Thought "huge boat anchor". I am so glad I did and not sure id get rid of it. It walks through a big oak like its totally up for it. I am running 32 in .404.
 

WillG

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I will definitely try that suggestion of the plug wire. I love my 051 too. Was cutting red oak with it with a 21" and .404 Stihl RM and it went through like a hot knife through butter!


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WillG

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Finally figured it out. Loose intake block! Have a carb kit and intake gaskets coming.



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WillG

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Once she's back together and running again I'm also going to be installing a 36" Tsumura bar and Oregon semi chisel chain

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Carhartt

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I just bent a chain tensioner screw over the wknd on mine with a long bar. I assume I need to back it off after tightening the bar nuts. That saw just walks through that 28 in red oak. Not looking forward to splitting it up.
 

WillG

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Reassembled the intake and carb yesterday and it still wouldn't run. Plug was wet and it was popping out of the intake. Pulled the flywheel and found the flywheel key sheared. So it looks like I had 2 problems going on. I was able to extract the broken key from the crank and flywheel and inspection revealed no damage to the flywheel or crank. Ordered a new OEM Stihl key. Used blue loctite on the intake block screws.
f8416217c07c0cd30f709316690c7f15.jpg


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Carhartt

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Nice catch.
Mine shut off in a cut today. I am hoping it's a plug or a short in wire. It seems electrical. Guess it cld be a flywheel key also. Haha
 

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Just make you torque the nut back to 25.8 ft-lbs (35 Nm). Provided if you didn't have the torque valve @ hand.
 

Carhartt

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How many clicks is that with a Dewalt impact? I feel like 3 to 4. Haha
 

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:roto2palm:
Surely don't want try that with my Aircat. It hits 80 ft-lb + on the first hammer hit. Beside that why they made torque wrenches for.
:roto2cafe:
 

WillG

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I've got a factory service manual for mine

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AVB

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I've got a factory service manual for mine

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I was hoping you did. Kinda hard to trust anyone other than the OEM on service specs from their manuals.
 

WillG

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All back together and running! Test cut video tomorrow after work!

363780bfe7b012ec9022a81041e582a3.jpg
a7cfa0da886e9989a25e5c07e7b7107a.jpg
3c838ab8e725195c25d42d766349bc96.jpg


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