3120xp dies when I throttle

[internet.user.human]

What part of NC are you in ? I'm not terribly far from Charlotte.

Same, I’m actually in Huntersville.

 

[rogue60]

Looks straight gassed or to little oil in the mix combined with a non adjustable H

 

[cscltd]

No if you get a vacuum leak then the saw runs to lean and to hot as there is not enough fuel to cool the piston. Then the piston expands and contacts the cylinder and then smears it's self to the cylinder because there is no oil either.
I am putting a 3120 together i got in a bucket.
My first vacuum test failed on it,i heard they have a factory leak under the oiler.

FYI-Don’t forget, 3120 have the hole in crankshaft to lube sprocket bearing from crankcase. You have to seal (use ur thumb) to cover the hole wear sprocket bearing sits

 

[Bob Hedgecutter]

FYI-Don’t forget, 3120 have the hole in crankshaft to lube sprocket bearing from crankcase. You have to seal (use ur thumb) to cover the hole wear sprocket bearing sits

Are you saying the hole in the stub of the crank that the clutch screws to is open to the crankcase interior on a 3120- and does not just terminate at a depth that coincides with the clutch needle bearing and has a cross drilling at this position?

 

[cscltd]

I don’t see a lot of these tbh.
but I thought it didn’t have hole on end of crank like 266 etc. to lube sprocket bearing, rather hole on crank sprocket bearing surface fed from inside engine

 

[Bob Hedgecutter]

I don’t see a lot of these tbh.
but I thought it didn’t have hole on end of crank like 266 etc. to lube sprocket bearing, rather hole on crank sprocket bearing surface fed from inside engine

No I was just trying to understand what you were pointing out.
There are 3120 cranks designed for the 3120 powered cut off saw that have a complete drilling into the insides of the crankcase- I believe to allow gasses to exit and help keep the needle bearing free of concrete dust. These ones do and will be the cause of pressure/vac tests failing and (I think) rely on the sprocket drive to somewhat seal when in use.
Like you, I am not too familiar on the marque and can count on one hand the number I have worked on, but I did plug one such drilling with a bit of brass rod to seal the leak in a chainsaw power head once.

 

[internet.user.human]

Looks straight gassed or to little oil in the mix combined with a non adjustable H

I’m starting to get a sick feeling that you might be right. I went and checked where I store my gas and oil and I found a 6.4oz bottle of oil that’s unopened.

I’m almost sure that I mixed in some Husqvarna 50:1 because when I did I think I found the same bottle sitting there and realized I didn’t need to buy the one I had…but now I just don’t know.

Any way to know for sure that this is what happened and if so, what can I do about it?

Thanks,

J

 

[SteveSr]

I’m starting to get a sick feeling that you might be right. I went and checked where I store my gas and oil and I found a 6.4oz bottle of oil that’s unopened.

I’m almost sure that I mixed in some Husqvarna 50:1 because when I did I think I found the same bottle sitting there and realized I didn’t need to buy the one I had…but now I just don’t know.

Any way to know for sure that this is what happened and if so, what can I do about it?

Thanks,

J

Dump the gas out of the saw into a clean glass jar. See if it is tinted the color of the oil. 2c oil is usually tinted green, red, or blue so you can tell if it is mixed with the gas. Straight gas is weak pee yellow.

The way to fix this in the future is to always put the oil in the container BEFORE you add the gas. I also let the bottle drip into the can for a while.

For now just do the leak test and then pull the cylinder. Straight gas will show damage all the way around the piston. Lean running usually only the exhaust side. When you pull the carb to do the leak test you might be able to see the intake side of the piston through the intake manifold with a good flashlight.

 

[internet.user.human]

Dump the gas out of the saw into a clean glass jar. See if it is tinted the color of the oil. 2c oil is usually tinted green, red, or blue so you can tell if it is mixed with the gas. Straight gas is weak pee yellow.

The way to fix this in the future is to always put the oil in the container BEFORE you add the gas. I also let the bottle drip into the can for a while.

For now just do the leak test and then pull the cylinder. Straight gas will show damage all the way around the piston. Lean running usually only the exhaust side. When you pull the carb to do the leak test you might be able to see the intake side of the piston through the intake manifold with a good flashlight.

Whew! Ok, the fuel has a blue tint to it so I remembered correctly; I did add oil. So, I just have a spare bottle of oil.

I emptied the chainsaw fuel tank when I got home after the issue started and before I took off the muffler for the pics. Good to know I didn’t straight gas it, but I’m still at a loss as to what would have caused the original issue and symptoms. Like you, I usually empty the bottle of oil into the container beforehand just to make sure I don’t screw up, but this time I added after I bought the gas.

I’ll have to report back once I get the tools and get time to test everything. Question: can’t I perform the vac/pressure test without taking the whole saw apart? (Besides removing parts so I can spray some water on the leak prone locations.) I ask simply because I don’t have all the doohickeys to block the muffler port, etc.

On another note, I did adjust the idle when I was first starting to break in the saw early this year. I adjusted it by ear, and by having the saw just about to make the chain pull at idle but not quite. I don’t believe I adjusted the High or throttle screws but it’s been a while. But that shouldn’t have caused any kind of catastrophic failure of the fuel system right? Obviously there’s the scoring on the piston so something happened…but what?

Thanks for all the advice and help.

J

 

[Maintenance supervisor]

Really with a saw that new only a couple of things will smoke the piston like that.
Obviously strait gassed.
A hole or crack in the fuel line or impulse line.
Crank shaft seals cracked from dry rot or damaged.
Maladjusted carburetor.
And finally a dull chain ,believe it or not working a saw with a dull chain can ruin a saw.

 

[Maintenance supervisor]

Sorry ;loose fittings also, such as intake ,case,or cylinder.

 

[cscltd]

It does look more like a dull chain/not enough load result if fuel was mixed properly with fresh gas-but air leak or fuel starvation is possible
but I also wonder fast would dull chain scenario show up with original rev limited module compared to saw without?

 

[internet.user.human]

It does look more like a dull chain/not enough load result if fuel was mixed properly with fresh gas-but air leak or fuel starvation is possible
but I also wonder fast would dull chain scenario show up with original rev limited module compared to saw without?

It’s an Oregon chain and I’ve only used that particular chain one other time; I could still feel the edge in it when putting it on the bar. I usually use my dremel attachment to top up a chain sharpness before heading out but didn’t worry about it that day.

This happened in like the first 10 minutes of using the saw; besides the pinching in the cut the saw didn’t do much work that day haha.

 

[rogue60]

The 3120's are a relatively reliable saw as you say it was new when you got it.
From ya pics it's done bugger all work and definitely no signs of long hrs of continuous hard work.
The exhaust port and piston look very dry lacking in any visible oil residue. Why this has happened is an unknown as yet I hope you get to the bottom of it.
The 088/ms880 will start to smear piston onto the cylinder wall on the exhaust port side if run on 50:1 and worked hard but not as bad as the mess you have.
It's very odd what you have going on with such a low hr saw and a 3120 at that. You confirmed there was oil in the mix that only leaves some kind of massive air leak? that combined with 50:1 would give very little time before things start heating up and smearing piston onto the cylinder. But that's highly unlikely a massive air leak? being a proven reliable saw and so low hr.

Pull the cylinder to see if the intake side of the piston is scored.

 

[mossaw]

From reading all of these great posts and your observations/replies, you definitely have a lube problem. Even with 100:1 mix I don't think your could do this amount of damage in such a short time. Husky oil is a top shelf product and will work itself into the micro-finish of your new bore to do its job of protection even with a bad mix.

I would look for the empty oil bottle, and make double sure you didn't straight gas it. You should see a sheen of oil on the piston skirt and bore. 2-stroke engines will idle on straight gas, however when reved, the overheated main bearings act like a brake.

If I were you, I would be knocking on Husqvarna's front door. Good luck!

 

[internet.user.human]

From reading all of these great posts and your observations/replies, you definitely have a lube problem. Even with 100:1 mix I don't think your could do this amount of damage in such a short time. Husky oil is a top shelf product and will work itself into the micro-finish of your new bore to do its job of protection even with a bad mix.

I would look for the empty oil bottle, and make double sure you didn't straight gas it. You should see a sheen of oil on the piston skirt and bore. 2-stroke engines will idle on straight gas, however when reved, the overheated main bearings act like a brake.

If I were you, I would be knocking on Husqvarna's front door. Good luck!

I don’t believe I’ll be able to get warranty service as I don’t have a purchase receipt. I paid cash for it from a guy who won it in an auction lot from a lawn/tool supply dealer he worked for. No idea who that dealer was.

I think it might be on me to repair it. I bought the pressure test kit and now just need to get it on the bench and test it.

 

[Husky77]

Great saw well worth fixing and then change to something like Aspen. Its pre mixed and you cant go wrong. I see so many people having trouble with fuel related ruined pistons and they all say that fuel is expensive!! Not half as expensive as an engine rebuild.
You have a saw that's almost bomb proof it should last very many years in your hands. Good luck

 

[internet.user.human]

Hi all,



It’s been quite a year. Sorry to necro this thread but I finally have time to figure out what killed my saw. I have it on the bench to do a pressure/leak test but I’m having a heck of a time getting the clutch off. I have a piston stop in the cylinder and have used my socket wrench and impact driver (set for right hand tightening, for left hand loosening) to no avail. Any advice? Photos attached.





Thanks again for all your help.

 

[internet.user.human]

Hi all,



It’s been quite a year. Sorry to necro this thread but I finally have time to figure out what killed my saw. I have it on the bench to do a pressure/leak test but I’m having a heck of a time getting the clutch off. I have a piston stop in the cylinder and have used my socket wrench and impact driver (set for right hand tightening, for left hand loosening) to no avail. Any advice? Photos attached.

View attachment 1136677

View attachment 1136678

Thanks again for all your help.

Of course right after I posted, I got it off with some busted knuckles. Now to the fly wheel. Any pointers on what I need to seal up for the test? I have the spark plug/cylinder block and the carb plate block, but is the best way to seal the exhaust/muffler side just to use a piece of rubber between it and the cylinder?



Thanks!

 

[J D]

but is the best way to seal the exhaust/muffler side just to use a piece of rubber between it and the cylinder?

Yup