How to Free Up A Rusted Piston

#1
I have a 50cc 2 cycle engine that someone left the head off of for years and it rusted the rings in place. I have the head loose and raised off the block a bit so I know it's just the piston, not the crank.

I filled the top half of the cylinder above the piston with Evaporust and let it sit 24 hours. I repeated the process with the exhaust port and was even able to fill and soak the cylinder below the piston by turning the engine upside down.

The exposed cylinder is much cleaner but the piston rings are still stuck. Suggestions? Heat? Other chemicals that might penetrate? Brute force? I want to at least salvage the aluminum piston if possible.
 
#3
No brute force. Those rings will break. I agree with Bandit 40 with the trans fluid. A wooden dowel through the spark plug hole and a gentle tap might get the rings freed once the oil has sat for a while.
 
#4
Am I correct in saying you'd need to replace the rings?
Id disconnect the con rod. Put some ATF and acetone mixed 50 / 50 in the bore let it soak for 5 min. The put a nice solid piece of wood on top of the piston and give it a good whack with a 5lbs hammer.

Make sure the engine is on something firm and wear goggles
 
#5
you could always heat the jug a little along with the transmission fluid. You'd have to leave out the acetone though. If you're not in a hurry, fill it with a 50 50 mix and set it aside, giving it a tap or pry now and then.
 
#6
The rings will most likely need replacing anyway, but no way to disconnect the rod on this engine other than the wrist pin, and that is well within the cylinder. I'll give the ATF a try, and some moderate tapping. Thanks!
 

bikebudy

Banned - Must pay $500
#7
diesel fuel works quite well and will get into where most fluids can't

Use a wood block near the same size as the piston, hitting the center will only brake it. Strongest part of a piston is its sides.
 
#8
A friend of mine had a International Farmall H tractor that was locked up, I pulled the plugs and put Pinesol in all 4 cylinders jacked the back wheels off the ground and put it in third gear. Every day we would check the progress by grabbing the wheel and try to turn it,then about 5 days later the wheel turned and Pinesol blew out all 4 cylinders.When we pulled the head and wiped the pistons that Pinesol cleaned those pistons so good they looked like new and this was a 1958 Tractor! It is still running today.:thumbsup:
 

rmm727

Active Member
#9
A friend of mine had a International Farmall H tractor that was locked up, I pulled the plugs and put Pinesol in all 4 cylinders jacked the back wheels off the ground and put it in third gear. Every day we would check the progress by grabbing the wheel and try to turn it,then about 5 days later the wheel turned and Pinesol blew out all 4 cylinders.When we pulled the head and wiped the pistons that Pinesol cleaned those pistons so good they looked like new and this was a 1958 Tractor! It is still running today.:thumbsup:
I know someone who did something very similar but his was worse. They filled the spark plug holes with diesel fuel. Pulled the oil pan and then put a floor jack against one of the cranks counterweights. They heard it when it went pop.

I had a King Quad I got for $100 that was locked up. I filled the cylinder with Marvel Mystery Oil and let it sit for a few days. I then used a pry bar on the recoil starter pawl. I got it to run after that and it never smoked after the first startup.
 
#13
Get some naval jelly in there.
Its an acid and will devolve the rust.
Its not going to do any significant damage to anything its just a rust remover.

So let that sit a day and see if it loosens up.

Odds are your not in for an easy go.

I read one post here that said pound it.
I do not agree with hitting it with anything.
Odds are if you do you will destroy the piston.

What you can try is to fill the cylinder with oil and use a grease gun to push the piston out of the liner.

You will need to weld up a spark plug and thread in a grease fitting.

WARNING!!!!!!!!

You can really apply a lot of force like this.
If that piston does not move you can blow the head off with the kind of presure the grease gun can excert.
 
#15
Hot lead pour it in the cylinder let it solidify then use a block of wood and a hammer. the lead will not harm the piston or cylinder and it will provide heat for expansion as you drive the lead slug with the wood&hammer the piston and rod will come out if how ever the hammer does not work a jack bolt can be fixed using 1/4" plate and the head studs to pull the cylinder up freeing the piston let me know if you need pics of the tools


Sent from my iPhone using Morris code
 
#17
Hot lead pour it in the cylinder let it solidify then use a block of wood and a hammer.
I like this idea. I think I'll start with what I have on hand, pine-sol soak, then combine with lead protective layer and a hammer. I'd prefer not to scratch the cylinder if possible since oversize rings are not available. I might run the gamut of chemicals before I beat on it too hard. Thanks guys!
 
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