Stihl 066 Magnum got temperamental today

[chiefs584ever]

Was cutting some 36" rounds today with my 066 and when the saw got warmed up, it would bog down and lose power. It finally died all together.
After it cooled down, it started back up, but idles a bit rough.
Took it to the local saw shop for a diagnosis, but I have no idea what it might be.
Fresh fuel
Correct premix
Starts as normal.
Seems to have good compression

I am all ears if you all have some hints of what it might be.


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[merc_man]

Sounds like an air leak. Time to presure vac test it.

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[Wood Doctor]

Sounds like it's starved for fuel. First, replace the fuel filter, also known as the pickup body. It clogs up. Could be the fuel line, but I think it's the filter. I have a couple of Stihls that have done the same thing,

Try running it awhile with the fuel filter removed and see if there is any improvement.

 

[timbrjackrussel]

Was cutting some 36" rounds today with my 066 and when the saw got warmed up, it would bog down and lose power. It finally died all together.
After it cooled down, it started back up, but idles a bit rough.
Took it to the local saw shop for a diagnosis, but I have no idea what it might be.
Fresh fuel
Correct premix
Starts as normal.
Seems to have good compression

I am all ears if you all have some hints of what it might be.


Sent from my SM-N960U using Tapatalk

Check the fine screen inside the carb, it can be plugged if the fuel filter starts to fall apart on the inside.

 

[4seasons]

Cracked fuel line. Had the same problem a few years ago with one of my saws.

Also could be a spark plug going out. They start losing power when warm, then don't have enough spark to start. You can pull them out and they will spark out of the cylinder but not spark under compression in the cylinder.

 

[sb47]

Replace the plug. I know it's supposed to ether work or not work but my 290 was loosing power and getting hard to start. A fresh plug did the trick.

 

[GVS]

Replace the plug. I know it's supposed to ether work or not work but my 290 was loosing power and getting hard to start. A fresh plug did the trick.

First check or replace the S/plug then go with fuel filters and fuel line then the vac./pr.ck.

 

[user 122190]

This! A used saw I had a few years ago had similar problems. A tuneup kit had it working perfectly.

First check or replace the S/plug then go with fuel filters and fuel line (Added also an Airfilter) then the vac./pr.ck.

 

[4seasons]

First check or replace the S/plug then go with fuel filters and fuel line then the vac./pr.ck.

Don't waste time checking the spark plug. Just replace it and see it it is fixed. Spark plugs are cheap, and if it doesn't fix it it doesn't hurt to have an extra one on hand.

 

[Wood Doctor]

Don't waste time checking the spark plug. Just replace it and see it it is fixed. Spark plugs are cheap, and if it doesn't fix it it doesn't hurt to have an extra one on hand.

Agreed. I think I have run into one plug that refused to work right in five years. A few others were OK but they were screwed in only thumb tight, if that. I've actually had more trouble with broken plug wire connectors.

 

[v8titan]

+1. Replace plug first. A buddy of mine had similar symptoms and a new plug did the trick.

 

[Brushwacker]

All said I wouldn't rule out the ignition coil either. Seems to me about or after 20 years or so is life expectancy on a majority.
Doesn't hurt to remove the muffler and observe the pistons condition before spending money and time on more timely procedures also.

 

[chiefs584ever]

Holy crap does this saw run better now. Saw shop put the correct carb on it, a twin port muffler, new fuel filter and put a new trigger on it because it wasn't revving on start like it was supposed to.
I am estimating the saw cuts 30 percent faster now. Definitely modified from stock, but Tim's saw shop in Fort Madison Iowa woke this beast up!

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[NSMaple1]

Correct carb? How did it get an incorrect one?

 

[chiefs584ever]

Correct carb? How did it get an incorrect one?

It came from the factory with the incorrect carburetor. Saw was branded as a magnum, but had a regular 066 carb and muffler. I will be having a discussion with Stihl on monday.

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[GVS]

Correct carb? How did it get an incorrect one?

Now that's a good question.

 

[JeffHK454]

It came from the factory with the incorrect carburetor. Saw was branded as a magnum, but had a regular 066 carb and muffler. I will be having a discussion with Stihl on monday.

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I believe we’re going on 17 years since the 066 was produced I’m interested in hearing what Stihl has to say to ya.

 

[chiefs584ever]

I believe we’re going on 17 years since the 066 was produced I’m interested in hearing what Stihl has to say to ya.

I bought the saw brand new in 09. I was always disappointed in its fuel economy. Had to refuel every 3 cuts when cutting thru a 30" log. Since it came back from the shop, I am getting 10 to 12 cuts out of a tank.

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[JeffHK454]

I bought the saw brand new in 09. I was always disappointed in its fuel economy. Had to refuel every 3 cuts when cutting thru a 30" log. Since it came back from the shop, I am getting 10 to 12 cuts out of a tank.

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Wow..three big cuts on a tank of fuel stinks!

 

[Kevin in Ohio]

First thing I check is to loosen the fuel cap and try to start. have had quite a few saws I've worked on with the symptoms you have and it can be pulling a vaccuum causing it to starve for fuel. Stihl normally uses a screw and over time I guess they seal too good. Try running with a loose fuel cap. If it's fine then, I normally poke a few holes with a pin wear the top of the breather. Problem solved.