# Big chainsaw troubles..... help needed



## hemlock (Apr 10, 2013)

Hello,
It looks like my Husky 365 just bit the dust, and I can't figure out what happened.  It was cutting along just fine, then sputtered, rattled and died.  Tried to pull it over, and there was nothing.  The compression is completely gone (gage reads almost zero).  It was not straight gassed.  The only thing I can think of is an air leak some place, but it did not feel or sound lean.  What else might have caused this?  Any help would be great.  I think I'm about to cry.  Thanks


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## arngnick (Apr 10, 2013)

How new is the saw? I had a buddy that the same thing happened to him during the first year of owning the new saw. The dealer blamed it on old gas with ethanol in it. I think the reluctantly covered it onder warranty.


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## Ashful (Apr 10, 2013)

Rattle?  No compression?  sounds like a broken connecting rod.


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## hemlock (Apr 10, 2013)

Joful said:


> Rattle? No compression? sounds like a broken connecting rod.


 
Thats what I thought - but when I removed the plug and pulled it over, the piston was moving.


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## Nixon (Apr 10, 2013)

Pull the muffler and see what the piston looks like. You may have torn an intake boot ,or lost a crankcase seal .


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## MasterMech (Apr 11, 2013)

Joful said:


> Rattle? No compression? sounds like a broken connecting rod.


 
+1 on pull the muffler. Broken ring? Husky is still a single ring design no?

Check the decomp valve?


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## hemlock (Apr 11, 2013)

Pulled off the cylinder, and everything looks pretty good.  Is it likely a crankcase seal?


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## Ashful (Apr 11, 2013)

Just so we're not making any wrong assumptions, how exactly did you test compression?  Be specific.


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## MasterMech (Apr 12, 2013)

MasterMech said:


> Check the decomp valve?​


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## hemlock (Apr 12, 2013)

Joful said:


> Just so we're not making any wrong assumptions, how exactly did you test compression? Be specific.


 
With a gauge.  Pulled it over a few times.  It hardly blew anything.
Master Mech - I'll check the decomp.


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## HittinSteel (Apr 12, 2013)

Good news on the piston! Now you just have to find where its getting air.

Isn't compression made above the intake and exhaust ports? If so, what else could it be besides decomp, spark plug hole, cracked cylinder, stuck ring, ??????

I had the same situation on a saw I compression tested for a guy. Showed nothing on the gauge. Pulled the muffler and the piston and rings were in great shape. It stumped me (and he didn't leave the saw with me for further investigation).


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## thewoodlands (Apr 12, 2013)

hemlock said:


> Hello,
> It looks like my Husky 365 just bit the dust, and I can't figure out what happened. It was cutting along just fine, then sputtered, rattled and died. Tried to pull it over, and there was nothing. The compression is completely gone (gage reads almost zero). It was not straight gassed. The only thing I can think of is an air leak some place, but it did not feel or sound lean. What else might have caused this? Any help would be great. I think I'm about to cry. Thanks


How's your spark splug, did it blow out , might need a heli coil.


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## Ashful (Apr 12, 2013)

zap said:


> How's your spark splug, did it blow out


 
That's why I asked how he's measuring compression.  If it's not putting any compression on the guage, the spark plug is out of the equation.

If the decomp valve is good, then it's time to pull the jug!


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## smokinj (Apr 12, 2013)

hemlock said:


> It was cutting along just fine, then sputtered, rattled and died


 
"The rattle" Small sound Rings broke Big sound crank?????? Either way air leak is not going to be a rattle. Iam with Joful time to pull the head and hope its rings.


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## cnice_37 (Apr 12, 2013)

I'd check to see if the ring moves by using a small screwdriver and pushing it through the open exhaust port (you removed muffler already.)  My guess is its stuck, pretty common on these saws I believe.


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## Fiziksgeek (Apr 12, 2013)

My first thought would have been a lean seizure.


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## hemlock (Apr 12, 2013)

Put the cylinder back on and checked the decomp valve and it is also good.  Guess I'm bringing it to the dealer.  It makes no sense at all.  Everthing that would cause a compression issue checks out, but it has 0 psi.  I'm thinking something else is going on.  This is out there, but could the flywheel be turning on the crank, and with the plug/gauge in, it creats just enough back pressure to cause the flywheel to turn on the crank, but with the plug/gauge out, it allows the piston to turn over, due to no back pressure?  It's a stretch, but it all makes no sense otherwise.


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## MasterMech (Apr 12, 2013)

hemlock said:


> Put the cylinder back on and checked the decomp valve and it is also good. Guess I'm bringing it to the dealer. It makes no sense at all. Everthing that would cause a compression issue checks out, but it has 0 psi. I'm thinking something else is going on. This is out there, but could the flywheel be turning on the crank, and with the plug/gauge in, it creats just enough back pressure to cause the flywheel to turn on the crank, but with the plug/gauge out, it allows the piston to turn over, due to no back pressure? It's a stretch, but it all makes no sense otherwise.


 
Pretty easy to yank the flywheel and look for a sheared key.  Or just mark it and pull it over, recheck the marks.


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## Nixon (Apr 12, 2013)

MasterMech said:


> Pretty easy to yank the flywheel and look for a sheared key. Or just mark it and pull it over, recheck the marks.


Is that going to address the 0 compression ? Seems like a real mystery ..... 0 compression ,good decomp and plug , good P/C and rings .


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## MasterMech (Apr 12, 2013)

Nixon said:


> 0 compression ,good decomp and plug , good P/C and rings .


 
But Hemlock makes a good point that the flywheel could just be spinning on it's taper.  If it ain't rings, piston, cyl, decomp or spark plug, I'm open to slightly more exotic theories.


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## cnice_37 (Apr 12, 2013)

Check the ring!!


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## hemlock (Apr 13, 2013)

MasterMech said:


> Pretty easy to yank the flywheel and look for a sheared key. Or just mark it and pull it over, recheck the marks.


 
Thats what it is.  I feel like an idiot.  I marked the flywheel to the nut, gave it a pull as though starting, and the flywheel is spinning on the crank.  When you pull it over slowly or remove the plug, it grabs the crank and turns.  Thing is, is this good or bad - and can it be fixed?  Does anyone know the torque spec for the nut?


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## basod (Apr 13, 2013)

hemlock said:


> Thats what it is. I feel like an idiot. I marked the flywheel to the nut, gave it a pull as though starting, and the flywheel is spinning on the crank. When you pull it over slowly or remove the plug, it grabs the crank and turns. Thing is, is this good or bad - and can it be fixed? Does anyone know the torque spec for the nut?


 
Is the flywheel keyed to the shaft? If not the timing mark will matter.
If you figure that out remove the plug and use a piece of clothesline stick down in the plug hole this will prevent engine turning over during tightening

What size is the nut? rather the shaft thread(it's somewhere in the 1/2,9/16,5/8,3/4- ball bark standard size. Just close doesn't matter if metric
I'd assume it's fine thread as well. could be anywhere from 90-200ft-lbs (though probably newton-meters)

Definitely use some red(higher temp) threadlocker or similar when reinstalling


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## Ashful (Apr 14, 2013)

basod said:


> Definitely use some red(higher temp) threadlocker or similar when reinstalling


 
Definitely ignore anyone's home-grown ideas, and definitely follow the procedure in the shop manual.


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## hemlock (Apr 14, 2013)

I put the flywheel back on (you can still see where the key was), and torqued it down, and it fired up.  My question now is - is the key critical for power transmission, or is it strictly for timing?  My guess would be that being a tapered shaft, that the key is primarily for timing but still am not certain.  The key was cast right into the flywheel.


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## basod (Apr 14, 2013)

hemlock said:


> I put the flywheel back on (you can still see where the key was), and torqued it down, and it fired up. My question now is - is the key critical for power transmission, or is it strictly for timing? My guess would be that being a tapered shaft, that the key is primarily for timing but still am not certain. The key was cast right into the flywheel.


When it loosened up it wiped the key off the flywheel? I'd think the casting/machining would make it difficult to cast a key into a flywheel(could be wrong)

New flywheel is $76 here
http://www.partstree.com/parts/?lc=husqvarna&mn=365 Special EPA (1999-11)&dn=082960011

It's an M8X1 nut which I believe is 28-32N-m torque spec
If the flywheel moves it'll be the equivalent  of an engine "jumping time"
Except this one's spinning at what? 12k+ rpm - Hopefully there's enough safety margin built into the jug/casing to hold it together


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## MasterMech (Apr 14, 2013)

basod said:


> I'd think the casting/machining would make it difficult to cast a key into a flywheel(could be wrong)​


 
That's the way many small flywheels are made now.

Hemlock,

I wouldn't attempt to run the saw again until you get a replacement flywheel. The current flywheel will most likely shift position a bit every time the saw accellerates/decellerates and while starting. I would order a new flywheel and make sure the nut is torqued to spec. Definitely do not use loc-tite on that taper, as that will make future removal unnecessarily difficult.


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## nate379 (Apr 15, 2013)

I'd just cut a keyway into the flywheel before spending $75 on a new one!  If you aren't setup to do it, bring it to machine shop with a case of beer.


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## Ashful (Apr 15, 2013)

nate379 said:


> I'd just cut a keyway into the flywheel before spending $75 on a new one! If you aren't setup to do it, bring it to machine shop with a case of beer.


 
... also has a lower likelihood of shearing again, if you use a standard key in the new slot, versus a casting.


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## MasterMech (Apr 15, 2013)

Joful said:


> ... also has a lower likelihood of shearing again, if you use a standard key in the new slot, versus a casting.


 
Keep in mind that the shear strength of the key just may have been engineered into the saw to prevent excessive energy from being transferred to the crankshaft in the event it comes to a very sudden stop.  (although such an event would be rare on a saw.)  If I were to cut a keyway into the flywheel and locate or make a suitable key, it would definitely be an aluminum key.


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## mikefrommaine (Apr 16, 2013)

There are plenty of flywheels available on ebay for < $35. I'd just replace it and be done worrying about it.


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## hemlock (Apr 16, 2013)

Ordered a new flywheel.  Should be here in a couple of days.  I ran it for an hour or so with the old flywheel, but it made me noervous.  I think it was going slightly out of time.  It dieseled after shutting it off when I went to refuel.

Edit - of course, now I can't get the old flywheel off.  Is feathering it with a torch a bad idea?


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## MasterMech (Apr 17, 2013)

hemlock said:


> Ordered a new flywheel. Should be here in a couple of days. I ran it for an hour or so with the old flywheel, but it made me noervous. I think it was going slightly out of time. It dieseled after shutting it off when I went to refuel.
> 
> Edit - of course, now I can't get the old flywheel off. Is feathering it with a torch a bad idea?


 
Wedge it with wooden wedge driven in snug and back the nut off 1 turn.  Give it a good sharp rap with a hammer (The nut should be in position to protect the threads and the end of the shaft.) and it will pop loose.


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