# Chainsaw problems



## Lonesome00 (Dec 16, 2013)

I do not know much about chainsaws and I am now tasked with repairing one. 

Back story: a pine tree fell over in my yard and a friend loaned me a Stihl 039 that was beat down. It ran well if you stayed on the throttle but needed a lot of work. I was able to de-limb the tree before the saw just stopped cutting. The air filter had holes in it, the chain is dull, and it leaked the bar oil out when it sat over night. I have since adjusted the oil screw, cleaned it up, installed a new air filter, sprayed out the carb. Next time I go into town (if I remember this time) I will pick up a file for sharpening the chain.

Now here is the problem. I pulled the spark plug and it looked new, so I reinstalled it. When I had it all put back together I tried to pull start it. Instead it hung up and I was not able to get a full pull out of it. I checked everything I could think of and nothing appeared to be wrong. So I pulled the spark plug and it turned over fine. Even with the plug removed it sounds like it has great compression. I have a lot of experience with two stroke ATV engines but no these small equipment engines. When I reinstalled the spark plus, the same problem again. That spark plug is the same one it was running on before. Why now would it prevent the engine from turning over?


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## Fuzzy D Fellers (Dec 16, 2013)

Sounds like the exhaust is clogged.


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## Lonesome00 (Dec 16, 2013)

I never thoguht of that. Is it like a lawn mowere where I just replace the whole thing?


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## mattech (Dec 16, 2013)

Not sure about stihl, but husqvarna has a compression blow off valve on the side where the chain is. It looks like a black round knob.


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## Wild Turkey (Dec 16, 2013)

Stihls are notorious for getting plugged exhaust spark screens.
Ive removed almost all of mine. Check that. looks like a piece of door screen on the muffler.


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## rayjay (Dec 16, 2013)

You may have the crankcase full of gas which would hydrolock the piston once the plug is installed. Remove the plug and tilt the motor up so the sparkplug hole is facing down and pull the rope 10 or 15 times or until junk quits coming out the hole.

You should have the switch in the off position while doing this or whoof  FIRE FIRE !!

One suggestion on the chain. Buy a new one from a Stihl dealer. Only about $25.  The difference in cutting will amaze you.

Those are great saws but if it's been run much with holes in the airfilter then the cyl may be damaged.


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## Bilge Rat LT 20 (Dec 16, 2013)

The 039 is an older saw, a very good saw too.
Corn gas eats the carb rubber gaskets and sticks a little check ball.
The idle jet may be clogged too.
Clean and rebuild the carb then use non ethanol gas.

Pull the bar off and clean the bar and the chain oil passages to the bar on the side of the saw. Check the cap for the chain oil tank, make sure it's tight/not leaking.
My 039 has cut firewood at the farm for many years.
Corn gas tried to kill it, ran great for years then i had to rebuild the carb/replace lines each year for 2 years.  I started using marine gas and no more problems.


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## Lonesome00 (Dec 16, 2013)

Hydrolock crossed my mind as well. I di nto know how to clear it though. I will give that a shot. 

I wanted to pull the carb. However, I just cannot see how to take the dang thing off. I am aworried i will end up damaging something if I try.


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## feathersnantlers (Dec 16, 2013)

Don't forget Youtube has most of this stuff for you to watch and learn. It's helped with many mechanical devices.


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## Lonesome00 (Dec 16, 2013)

That is very true.


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## 280bst (Dec 16, 2013)

I would start with the clogged exhaust screen, not being smart but when you took the spark plug out did that compression ring by chance come off causing it to go too far into the head. Good Luck just my 2 cents


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## Lonesome00 (Dec 16, 2013)

The whole muffler is claer. I pulled it and checked it out. I thought about the ring as well. It is intact.


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## The Longhunter (Dec 16, 2013)

I'm going with hydrolocking also.

I'd drain the gas, remove the plug, let sit overnight with gas cap off, then replace gas and plug.


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## Lonesome00 (Dec 17, 2013)

Nothing came out though when I removed the plug and muffler.


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## rayjay (Dec 17, 2013)

Long reach plug in a short reach head ???  I have seen spacers to make this possible. Then somebody pulls the plug and the spacer falls off...... The ground electrode would be bent down. Unlikely but ?????

These things do have a lot of compression and take a healthy pull on the rope.

Crap like this is one of the reasons I don't loan out or borrow anything with an infernal combustion engine.


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## Lonesome00 (Dec 17, 2013)

I agree, I hate barrowing stuff like this.


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## 1gr8bldr (Dec 18, 2013)

The Longhunter said:


> I'm going with hydrolocking also.
> 
> I'd drain the gas, remove the plug, let sit overnight with gas cap off, then replace gas and plug.


It's called "Hydraulic locking". You were real close.  Like a hydraulic cylinder. To much fuel getting in the cylinder acting like a hydraulic cylinder. Very common problem.


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## Backlasher82 (Dec 18, 2013)

1gr8bldr said:


> It's called "Hydraulic locking". You were real close.  Like a hydraulic cylinder. To much fuel getting in the cylinder acting like a hydraulic cylinder. Very common problem.



Hydrolock is a commonly used term by mechanics.


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## Lonesome00 (Dec 18, 2013)

I have rulled that out. I am sure it is a mechanical problem now.


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## 1gr8bldr (Dec 18, 2013)

Lonesome00 said:


> I have rulled that out. I am sure it is a mechanical problem now.


The fact that it turns freely with the spark plug out is indicative of Hydraulic locking. Let us know what you find or how you fix it. This same question came up a month ago on the motorized forum


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## Lonesome00 (Dec 18, 2013)

I thought because I cleared the cylinder, then had the same problem it was not hydrolocking.


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## NE GA Pappy (Dec 18, 2013)

2 cycles work by the fuel/oil mixture traveling through the crankcase first. The oil in the fuel/oil mixture is what lubes the bearings in crankcase.  If the crankcase gets flooded, then the piston/rings are compressing the fluid in the crankcase.... thus the reason for it feeling like it has compression with the plug out.

I am pretty certain you have the crankcase partially flooded with liquid, and causing the problem.  Drain the fuel tank, pull the plug, out and let it sit for several hours.  As long as there is fuel in the tank, it could migrate into the crankcase.  Before you try to start it again, after it has sat, turn the saw upside down, with the plug out, and pull the cord a few times to make sure it is cleaned out.  Put it back together, and pray it cranks.   Return to neighbor and vow to never borrow it again.


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## Lonesome00 (Dec 19, 2013)

Gatcha. I will try it that way this time.


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