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.

Sent from my SM-N960U using Tapatalk

Sent from my SM-N960U using Tapatalk

 

[pioneerguy600]

Better check the piston and cylinder for scoring, just pull front off the muffler.

 

[RajElectric]

Fuel filter?

 

[grizz55chev]

Dull chain.

 

[jr27236]

Better check the piston and cylinder for scoring, just pull front off the muffler.

Second that, sounds like maybe it scored and when it heats up it loses compression. It's at the shop now but I would of pulled the muffler to have a peak. If that looked good, compression check cold and warm if able to start.

 

[chiefs584ever]

Dull chain.

Brand new chain

Sent from my SM-N960U using Tapatalk

 

[grizz55chev]

Brand new chain

Sent from my SM-N960U using Tapatalk

Let’s see a close up pic of it.

 

[chiefs584ever]

Second that, sounds like maybe it scored and when it heats up it loses compression. It's at the shop now but I would of pulled the muffler to have a peak. If that looked good, compression check cold and warm if able to start.

When I let it cool, it started fine, but had a rough idle.

Sent from my SM-N960U using Tapatalk

 

[jr27236]

When I let it cool, it started fine, but had a rough idle.

Sent from my SM-N960U using Tapatalk

I would say it has low compression by what you are describing, if it were a air leak it would of took off on you and accelerated.

 

[Natster]

Clogged jet in carburetor. Made it run lean. Maybe lean run hurt piston?
Always add 1 tsp motor oil per gallon of gas. In addition to stihl 2 stroke oil. Have to open the Jets a little, but it can save a lean run. If it ain't smokin, it ain't right!
N

 

[1Alpha1]

It's a chainsaw! That's what chainsaws do.

On a more serious note, I hope it's not too bad whatever the problem might be.

 

[Colt Marlington]

I had a saw get out of tune(lean) all of the sudden after years of running perfectly.
And it caused it to run hot. And was hard to start.

Luckily I didn't push it. Checked the cylinder and piston and all was well. So I richened it up and back to running perfect.

Not sure what caused it to get out of tune. Don't recall changing ratio or anything. Maybe just sitting for a while and some gum formed around the needle that loosened up when I made adjustnents? I don't know.

 

[oaky]

yeah what pioneerguy said, an impulse line or crank seal may of cracked and thats all it really takes to mess up your mixture.
old rubber parts love splitting in winter.

 

[oaky]

if air filters clean that is..

 

[ericm979]

If the carb was set correctly when the ambient temperature was hot and you run it in cold weather without adjusting the carb, it'll be lean. You may have lightly seized it.

Adding regular motor oil to premix is a bad idea. There's a bunch of reasons why we use specific two stroke oil now and not regular 30wt. If you want more oil, put more two stroke oil in.

 

[jr27236]

If the carb was set correctly when the ambient temperature was hot and you run it in cold weather without adjusting the carb, it'll be lean. You may have lightly seized it.

Adding regular motor oil to premix is a bad idea. There's a bunch of reasons why we use specific two stroke oil now and not regular 30wt. If you want more oil, put more two stroke oil in.

What?? Because of the colder denser air your saying?

 

[drf255]

What?? Because of the colder denser air your saying?

Yes.

Saws tuned in the cold at lower elevations will be pig rich in warmer temps and higher elevations. And vice versa. The lean tune will sound ok until the saw gets hot, then it will be lean.

Many of learned this the hard way at the MMWS 2017 & 2018 GTG. I’m at 230’ asl and tuned my saw/drilled carb jets at 50* ambient temp. My saw couldn’t be leaned out enough at the gtg. With the H all the way in, I couldn’t get above 11k (I was at 14k with 3/4 needle to go at home).

The GTG had a temp of 88*and was at 2300’ ASL. I had to buy a stock carb to get my saw to tune.

 

[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!

Sent from my SM-N960U using Tapatalk

Sent from my SM-N960U using Tapatalk

 

[oaky]

it running before with the wrong carb?

 

[chiefs584ever]

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.

Sent from my SM-N960U using Tapatalk

Sent from my SM-N960U using Tapatalk