How to unstick small 2-stroke motor?

[Black88GTA]

So, I got a gas powered 2-stroke Craftsman leaf blower for free from a co-worker. The only problem - the motor is locked up.

The story goes, his brother in law and family were all over his house this past weekend. It was nice outside, so the BIL and my coworker decided to go out and do yardwork, put up lights and clean gutters and such. The BIL started off blowing leaves - but ran the blower on straight gas with no oil mixed in for about 5 minutes (the gas: oil ratio on the motor is 40:1, if it matters). My coworker realized what he had done, turned the blower off, replaced the regular gas with the proper pre-mix, and fired it back up. It seized up a couple minutes later. It's only been seized for a few days now, so I think (hope?) it should be relatively easy to free it.

Does anyone have any good ideas on how to unstick it? I've heard spraying lots of PB Blaster down the spark plug hole and allowing it to soak for a few days will do the job - which is good, because I have that here already. But, I wanted to get more opinions before I start attacking it. Is there something better than PB Blaster that I could use?


*******************12/14 UPDATE************************

I finally got a chance today to pull it open and look at it. There's definitely some cylinder and piston damage. I think I can re-use the piston...not sure about the cylinder.

I tried a few different things to get the aluminum deposits off of the cylinder walls...nothing worked. I ended up using an 80 grit flapwheel on it. There's still slight gouges in it so it probably still won't work, but...I'm probably looking at getting a new cylinder anyway, so meh.

After I had it apart to look at it and clean up what I could, I coated all moving parts with a light film of 15w-50 Mobil 1 synthetic and slapped it all back together. I tried pulling the cord with the spark plug disconnected, and it feels like there's more compression than before...but, I didn't want to attempt starting it, as it was 1:30 am at this point. I'm going to try to start it tomorrow and see if it works.

As promised, pics of damage:

Before I really tore into it
Another angle

I then pulled the motor out the rest of the way and took the head off...

Piston from the top
Piston damage. Notice the aluminum mushed into the ring.
I pulled the ring out and carefully cleaned out the groove with a dremel + cut-off wheel. The ring slides freely again.
Damage to cylinder wall
I cleaned it up...looks much better now

 

[xalos]

PBlaster works fine.. You might not even have to let it sit for very long maybe even just a little bit. But, make sure the piston isnt welded to the cylinder. If it is you will have to clean up the burrs.

 

[boomerang]

Originally posted by: xalos
PBlaster works fine.. You might not even have to let it sit for very long maybe even just a little bit. But, make sure the piston isnt welded to the cylinder. If it is you will have to clean up the burrs.

I can just about guarantee that not only is the piston welded to the cylinder wall, but that the rings are smeared and fused into the piston. On top of that, that same oil/gas mixture lubricates the lower end of the motor too. There's a real possibility the crankshaft and all its associated bearings are toast too.

There's certainly no harm in trying to get it apart, but I can guarantee it will never run again with the parts that are in it now. Probably not cost-effective to repair it too.

Having said all that, I'd give it a go if it were mine! I would too.

Edit: Separate the cylinder from the crankcase. Raise up the cylinder and block it up in place. With a dull ended drift, pound down through the spark plug hole on the top of the piston. Use something with a dull flat end so you don't pop through the top of the piston. You won't damage anything that isn't already damaged. Block up the cylinder carefully so you don't damage the crankcase. You mess that up and you'll need a replacement engine. By that I mean it will most definitely be more expensive to replace than repair. If the piston locked at the top of the bore, you won't be able to raise the cylinder. Good Luck!

Many decades ago, I used to repair Stihl chainsaws.

Edit2: If you get it apart and the crank and rod assembly and it's bearings seem to be OK, and assuming you can salvage the rest by whatever means, you might want to consider replacing the crank seals. There are two compression cycles on a 2-cycle engine. As the piston goes down, it compresses the oil and gas mixture that was drawn into the crankase. That fuel is then forced into the cylinder as the piston drops low enough in the bore to uncover a port. As that piston then travels up, it creates a vacuum in the crankcase drawing in more fuel. The point is that the crank seals, seal against both pressure and vacuum. Their failure is the most difficult thing to diagnose in a 2-cycle engine. You can't tell if it's the carb or compression or what.

I'm not sure how long those seals will hold up without lubrication.

 

[3chordcharlie]

She's dead, Jim.

Wait, I mean 'good luck'.

But it's broken.

 

[IHateMyJob2004]

Having watched these things get repaired, sometimes you get lucky. You might simply need to free things up. Get out a hammer.

 

[apac]

If Tool Time has taught us anything, it's that there is a right and a wrong way to fix these things, and the right way always involves explosives and/or oversized power tools. Good luck!

 

[Modelworks]

This takes a few steps to do but has worked on a couple lawn mowers, also works for stuck valves.
Get a fitting that matches that of the spark plug that can be adapted to a hose from an air compressor. Put the lightest machine oil you can find in the cylinder through the spark plug hole. Slowly increase air pressure and use a gauge , you should see pressure build then drop as the oil is forced into any openings. Sometimes it works better than others. We used kerosene, but be careful as kerosene can ignite without a spark under pressure. Worst case an aluminum rod inserted through the hole and tapping on the piston. Aluminum recommended since it will not harm the piston as much as other metals.

 

[Crucial]

I got a brand new toro CCR3650 GTS snow blower for free this way. First tank of gas the idiot ran straight gas in it and melted the rings. He didn't want to deal with it so he gave it to me and said I could have it if I could fix it. $25 for a new piston and rings and a freshly honed cylinder later I had a perfectly running $500 snowblower!

 

[randay]

Originally posted by: apac
If Tool Time has taught us anything, it's that there is a right and a wrong way to fix these things, and the right way always involves explosives and/or oversized power tools. Good luck!

so just run some jet fuel through her?

 

[Black88GTA]

Thanks all for the replies! Turns out it wasn't stuck all that badly. I sprayed some PB Blaster in there, and let it sit for maybe 20 minutes (I was impatient) Then I took the muffler off, exposing part of the piston, so I could see better what was going on. Then, I used a rubber mallet and placed a Sharpie (yes, a marker...I know, I know) thru the spark plug hole and firmly tapped on it...I felt the piston move a bit. Then I pulled the plastic outer casing off and turned the blower wheel in the direction of the motor rotation, and the piston started moving. Once I got it initially moving, it moved very freely...by pulling the cord on the machine, you could never tell there was ever anything wrong with it.

Well, except for the fact that it still won't start, of course . The PB Blaster I shot all over the top of the piston was coming out the exhaust port, so the ring is not sealing. I was able to see part of the cylinder wall / ring through the mount for the muffler, and I did see some gouging on the piston / ring. So I'll have to replace at least the ring, maybe the cylinder too. From what I can tell, the piston is probably OK.

Next step...get a few parts, and start rebuilding...

 

[bobdole369]

The PB Blaster I shot all over the top of the piston was coming out the exhaust port,

On a 2 cycle, its supposed to. There aren't any valves, just ports. If it weren't coming out I'd say you had a problem. Recall that the exhaust port is about halfway down the cylinder wall and is open the the combustion chamber. The intake port is further down.

Take out the spark plug. Stick ur thumb in there like a rube. Rotate the engine. If you cannot keep your thumb over the plug hole while ur buddy yanks it - ur rings are fine. There are only 2 compression rings on a 2 cycle and some gouging won't kill em. Once you fire it up she'll smooth out. After all its free right?



OMFG thats so redneck....

In reality by not using oil in the gas the cylinder walls heated up and sort of flash welded to the piston. It's bad for the motor, but she'll fire again.

 

[Black88GTA]

Originally posted by: bobdole369
The PB Blaster I shot all over the top of the piston was coming out the exhaust port,

On a 2 cycle, its supposed to. There aren't any valves, just ports. If it weren't coming out I'd say you had a problem. Recall that the exhaust port is about halfway down the cylinder wall and is open the the combustion chamber. The intake port is further down.

Take out the spark plug. Stick ur thumb in there like a rube. Rotate the engine. If you cannot keep your thumb over the plug hole while ur buddy yanks it - ur rings are fine. There are only 2 compression rings on a 2 cycle and some gouging won't kill em. Once you fire it up she'll smooth out. After all its free right?



OMFG thats so redneck....

In reality by not using oil in the gas the cylinder walls heated up and sort of flash welded to the piston. It's bad for the motor, but she'll fire again.

Hmm, you're right...I'll admit, I'm not too familiar with 2 strokes, so I assumed the worst. It does seem to have compression when I put my finger on it. One of these days, I'll have to get a real compression tester.

I tried forever to fire it up...it sounded like it almost caught a few times, but it never actually ran. Maybe just flooded out? Or still has too much PB Blaster in it? At any rate, I'll give it a day to dry up some, and I'll try it again tomorrow. I think the guy at work is gonna be pissed if I get it running

 

[compuwiz1]

If it siezed up due to lack of lubricant, good luck. Someone probably forgot to mix the appropriate amount of oil with the gas. When that kind of friction occurs, there's not much worth saving in there. That piston will not piss, sorry dude!

 

[bobdole369]

Maybe just flooded out?

QUite likely. If a 2 stroke doesn't fire right away it does exactly that. PB Blaster would tend to help things albeit not by exploding, but by helping to actually seal the combustion chamber.

You have the right idea. Try another spark plug too. And use new gas if you haven't already.


That piston will not piss, sorry dude!


Ehhhh, I beg to differ. Granted its possible theres a gaping hole in the piston or the skirt melted, but lets see what happens tomorrow.

 

[Black88GTA]

I don't have another plug handy...I would buy another, but the one in there already looks pretty good. I did take a dremel with a wire brush and clean up the electrode some before reinstalling it. The gas is good - after the mistake was discovered, my coworker drained the regular gas, refilled it with the proper mixture, and continued running it on Saturday when it seized up. It has about 1/2 tank left, and the gas is ~3 days old.

I got a pretty good look at the top of the piston through the exhaust port / spark plug hole, and it looks relatively undamaged. I saw a bit of gouging on the side that passes over the exhaust port, but it doesn't look really severe. From what I can see of the cylinder walls, they look pretty smooth too. The piston froze up about 1/2 way down the bore, so I was able to get a look at the area where it stuck through the exhaust port, once the piston was out of the way. The part I can see looks OK... but I couldn't see all of it.

Unsticking it took very little effort, so I'm hoping that the damage was minimal (although there certainly was some damage done).

 

[Eli]

It's toast. It will need a new top end, not worth it.

 

[Eli]

Originally posted by: Black88GTA
I don't have another plug handy...I would buy another, but the one in there already looks pretty good. I did take a dremel with a wire brush and clean up the electrode some before reinstalling it. The gas is good - after the mistake was discovered, my coworker drained the regular gas, refilled it with the proper mixture, and continued running it on Saturday when it seized up. It has about 1/2 tank left, and the gas is ~3 days old.

I got a pretty good look at the top of the piston through the exhaust port / spark plug hole, and it looks relatively undamaged. I saw a bit of gouging on the side that passes over the exhaust port, but it doesn't look really severe. From what I can see of the cylinder walls, they look pretty smooth too. The piston froze up about 1/2 way down the bore, so I was able to get a look at the area where it stuck through the exhaust port, once the piston was out of the way. The part I can see looks OK... but I couldn't see all of it.

Unsticking it took very little effort, so I'm hoping that the damage was minimal (although there certainly was some damage done).

ANY gouging to the cylinder wall is "severe".

It should be as smooth as glass all the way around.

Can't compare 2 cycles with 4 cycles. They won't take half the abuse before dying.

A 4 cycle will run on as little as 50PSI of compression.

You would be lucky to get a blip out of a 2 cycle with 80PSI.

 

[Damn Dirty Ape]

Originally posted by: Black88GTA
So, I got a gas powered 2-stroke Craftsman leaf blower for free from a co-worker. The only problem - the motor is locked up.

The story goes, his brother in law and family were all over his house this past weekend. It was nice outside, so the BIL and my coworker decided to go out and do yardwork, put up lights and clean gutters and such. The BIL started off blowing leaves - but ran the blower on straight gas with no oil mixed in for about 5 minutes (the gasil ratio on the motor is 40:1, if it matters). My coworker realized what he had done, turned the blower off, replaced the regular gas with the proper pre-mix, and fired it back up. It seized up a couple minutes later. It's only been seized for a few days now, so I think (hope?) it should be relatively easy to free it.

Does anyone have any good ideas on how to unstick it? I've heard spraying lots of PB Blaster down the spark plug hole and allowing it to soak for a few days will do the job - which is good, because I have that here already. But, I wanted to get more opinions before I start attacking it. Is there something better than PB Blaster that I could use?

that thing is toast.

 

[RocksteadyDotNet]

Submerge the whole block in diesel for about 6 months.

 

[Colt45]

new oversize piston, rings, and hone the cylinder.. not worth it.

 

[Black88GTA]

UPDATE: I tried it again today, after allowing it to sit since last night. It was soo close to catching, but never did. I got it to "run" for a couple seconds a few times, but it always dies.

I'm going to tear into it a bit more over the weekend... I feel like a dumbass going out in the front yard at 11:00 at night trying to start up a leaf blower. If I can't get it going like it sits by Monday, I'm going to tear it down and see exactly what it needs. A new piston ring is $3.49, and a new cylinder is $28.25 according to the Sears website. If the cylinder is visibly damaged, I'll try replacing that...but I'm definitely going to try a new ring first at the very least.

The full model number is 358.797180 if anyone cares

 

[SuperjetMatt]

I have a few years experience repairing blown 2-strokes.
First, the crank is most likely fine. Lack of oil does hurt the crank bearings and wrist pin bearings, but the piston/rings usually go first, so there isn't enough time for the bearings to get farcked up (USUALLY!)

If you want to fix it right, you should take the cylinder (without piston) to a machine shop and have them tell you what size piston to order - they will be able to judge how much they need to overbore the cylinder in order to get past the damage.
Then, order the appropriate oversize piston and take it and the cylinder back to the machine shop for boring. They need to have the piston in order to properly clearance the new bore.
After that, reassemble, break in, and be happy.

Or, buy new. Probably cheaper.

 

[Black88GTA]

Originally posted by: SuperjetMatt
I have a few years experience repairing blown 2-strokes.
First, the crank is most likely fine. Lack of oil does hurt the crank bearings and wrist pin bearings, but the piston/rings usually go first, so there isn't enough time for the bearings to get farcked up (USUALLY!)

If you want to fix it right, you should take the cylinder (without piston) to a machine shop and have them tell you what size piston to order - they will be able to judge how much they need to overbore the cylinder in order to get past the damage.
Then, order the appropriate oversize piston and take it and the cylinder back to the machine shop for boring. They need to have the piston in order to properly clearance the new bore.
After that, reassemble, break in, and be happy.

Or, buy new. Probably cheaper.

Good info on the crank / bearings. I was betting that those were OK, since everything spins really freely, with no weird noises or binding / scraping when you yank the cord.

About the cylinder / ring / piston damage. If I had to go through all that...you're right, it would probably be cheaper and less hassle to buy a new one. But the cool thing is, I can apparently get brand new parts directly from Sears...rather than mess around with a machine shop / overbore piston, I can just get a whole new cylinder assembly / piston ring / piston if necessary. I'm hoping to get away with only replacing the ring. If I can't get it going, I'll tear it apart and inspect the cylinder more closely for damage.

If I do so, I will post pics of the carnage (or lack of it)

 

[Liet]

As someone completely clueless about all this, I'd like all the posters in this thread to know that you're geniuses. What, did you all take classes or something?

 

[Black88GTA]

Originally posted by: Liet
As someone completely clueless about all this, I'd like all the posters in this thread to know that you're geniuses. What, did you all take classes or something?

Why, yes...a 2-year degree from the accredited institution of "fix your busted-up old ass car yourself as cheaply as possible, or you go back to riding the school bus again"

The school bus was death. 1000x more so when you were of legal driving age with a license. Branching out into other somewhat related types of machinery is just the natural progression of things. Oh, and having a healthy interest in this stuff helps too...