Help! Huskvarna 365 just seized...

[MrMoMo]

Ok, ok, before we all get the "go by a sthil" going.... this saw has been working great for me for the past 8 or so years... I have cut 3 cords of wood this year and no signs of giving up. I just went out to cut some more wood and it quit.... (no odd noises, just shut down quit, and won't roll over) Chain brake is not on! I am using the same fuel jug as I have used the past month and a half (so not a mixture issue).

When it quit it was not violent, it just started slowing down... then shut off - like it ran out of fuel. It was HOT, I could tell - the bar oil was dripping off like it was bleeding, and once I set it down, there was light smoke coming out the pull start side. I tried to pull it over and it didn't move. I didn't try to force it.

The ONLY thing I noticed odd, was it went through a LOT of fuel, about 1/2 a tank in 10 minutes - normally its really good on fuel.


So... while its coolding off - and before I start tearing it apart.... what are your guesses of what caused this, and what the damage is...

 

[D'Animal]

Remove the muffler and look at the piston.


I can give you about 100 reasons or faults that can cause a chain saw to seize the motor.

 

[D'Animal]

Here is my suggestion/guess.


You did not just seize this morning. It actually seized and the last time you used it. The piston was scored and the rings were stuck. Due to basic thermal dynamics, the steel compresion rings cooled at a different rate than the aluminum piston. Many times the rings unstick during the cooling process. The next time you go and use the saw, it may be hard to start and it will consume fuel like there is a hole in the tank. It takes more power/fuel to turn a seized engine than a free wheeling engine. The blowby of the stuck or partially stuck rings will not allow for full power.


Now that you are saying "O Crap"!

Make sure your clutch did not come unscrewed and is locking up the motor.

 

[MrMoMo]

Hmm, interesting theory....

Will check the clutch next. There is still a big pile of wood waiting for me!!! (Doh)

Picture of the piston through the exhaust, and through the plug hole. Nothing horrible from what I can see...

The saw started as easily this time as it ever has - and I'm wondering if I actually do have a hole in the tank, as I fueled it up last time I used it, just before I quit, but this time the tank was almost empty before I started (though the chain oil was no where near empty)

Can't push the piston down through the spark plug hole.

Going to pull apart the pull start and clutch now.

 

[D'Animal]

Dont take the cylinder off.

Remove the starter and make sure something did not get wrapped around the flywheel.

Do the same on the cluctch side.

Rope used to bail hay will stop a chain saw of it gets wrapped around the crankshaft.

 

[MrMoMo]

Doh... too late! Though it was needed!!

Pulled the pull start off and it was stuck, but that wasn't the problem. Once I removed the pull start I could move the flywheel, but couldn't make a rotation.

Pulled the head. Found a nice small chunk of steel sitting on top of the piston, which appears to have been bouncing around for a few strokes. No damage to the cylinder walls, just the top (which I assume is no problem)

So, thinking that maybe somehow this had stalled it I got happy for a few seconds, thinking just pull it out, put it back together and ta-da.. then I thought... but where did it come from??

It wasn't from the spark plug. It wasn't from the ring. Hmmm. Tried turning the flywheel over while supporting the piston. Crunch... grind... Um... yikes.

Looks like I shredded a bearing between the con-rod and crank. Not exactly sure how to proceed from here!!

Is this something that just happens after a while? is it a faulty part? or is it something that could have been prevented?

 

[D'Animal]

Your lower rod bearing is bad. You have to replace the crankshaft.

 

[fj40charles]

Your lower rod bearing is bad. You have to replace the crankshaft.

Is that a nice way to say, "time to buy a Stihl?"

 

[MrMoMo]

Should I replace the piston & con rod while I'm in there? (any estimate of cost for this surgery?)

 

[D'Animal]

It looks like they are around $270.

Parts and Diagrams for Husqvarna 365 Special EPA (1999-11)

 

[D'Animal]

Should I replace the piston & con rod while I'm in there? (any estimate of cost for this surgery?)

That bearing is a non replaceable part. It comes inside of a new crankshaft.

 

[D'Animal]

Wow I sure can kill a thread.




Im waiting for the "What Caused it" question.


The simple answer is RPM.

 

[MrMoMo]

So... what caused it? (have it mostly apart now)

And who wants to donate to my "Fix the Saw fund" I take paypal... (This is gonna hurt!)

I'll take another picture of the con rod once it's out. it's got some cool colors on it!

So, if it was RPM, what caused my saw to over rev? I wasn't running any faster than normal...

 

[D'Animal]

But what is normal RPM?

The Johnsered 670 Turbo is the world fastest production saw at 15,000rpm (and that was in 1986). (The Husqvarna 266 is the same saw but detuned a bit). The lower end bearings of any saw does not last at that RPM.

The Only lower Rod bearing failures I have seen in 25 years are on pro loggers saws who had the top end and main bearing replaced several times.

Or

They use poor quality mix oil. If you want the knock the lower bearing out of a hi-rpm/hi-load 2-cycle ngine, run Echo oil. If you want it to happen faster, use Champion oil.


No Load RPM or free wheeling engine speed is what kills more saws than anything. Even if the engine will run 14,000 rpm, most saws develope maximum torque between 9,000 and 9,500 rpm.


Im not saying you did any of this. You got 8 years of wood cutting out of a mid size Pro saw. Metal fatigue may be a factor.

 

[MrMoMo]

Interesting... I can't recall what type of oil I am using right now, but I'll check. I generally don't tend to rev the saw like crazy - I'm not a fan of High RPM... I didn't notice it running faster than it normally would, but I suppose that 1000 RPM higher over a duration of time, would have the same effect without noticing....

Now to get the clutch off... Man there is a lot of gook in a lot of little places!

 

[D'Animal]

Clutch comes off to the right.


(That is why I told you to not remove the cylinder and piston, way easier when you can lock the motor up.)

 

[MrMoMo]

Ahh, it screws on, I thought it was pressed. Pretty easy to put the cylinder back on at this point..., then what, shove something through the exhaust to stop it from rotating? Is the flywheel pressed on?

 

[D'Animal]

After the cylinder is on, stick the start rope or something into the spark plug hole. Make sure it does not stick out the exhaust or intake port.

Take the nut off the flywheel, the flywheel is a tapered fit into the cranshaft. Since your crankshaft is junk, you can smack the end of the crankshaft with a small ball peen hammer and the flywheel will come right off.

 

[MrMoMo]

And how do I make myself a handy dandy clutch removal tool....

(come on, I know you have a trick for me to use!! - you've got one for everything else!)

Thanks a ton for everything so far by the way!!

 

[D'Animal]

Is yours the one continus spring or the three shoe design?

Take a pic, please.