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Unseizing a vertical 2 stroke

Scotty 2

Registered
Hello all
How do you unseize a really seized blind headed vertical 2 stroke engine (similar to a 5hp Sunshine) where the piston is stuck at the bottom of the stroke?
I've tried oiling and heating and lifting and pulling and bumping to no evident effect after 2 months.

No suggestion too stupid....actually the suggestion of smashing the piston is out of the question.

Cheers Scott
Why is it that easy to get to bolts never get stuck and the bolts that are a pain in the neck to get a spanner on are stuck? :confused:
 
Last edited:

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
I have not tried this yet, but next really seized engine may. Fill with evaporust and wait:shrug:. I know with some rusted fasteners that are seized tight, after a soak in evaporust they come apart by hand. To try you might need to flush out any oil, evaporust does not seem to work well on oily rust.
 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
If the cylinder is removable get a piece of pipe to fit the bottom of the piston, put it in the press pushing the piston inward. Apply pressure, if nothing moves start heating the cylinder while under pressure, it should move, it will then be possible to pull it out. If no luck, next step is to heat everything, build a wood fire around it, let it burn out and cool. This will ruin Babbitt bearings.
 

davob

Registered
Another option is warm up the cylinder, then pack the back of the piston with dry ice pellets and acetone if you can get them. Should shrink the piston enough to get some movement, once it starts moving your on the home run. Have used this technique successfully a couple of times, and it may be on the cards again for Tangye and OA Bagshaw that are being stubborn.
 

K-Tron

Registered
It would probably be a good idea to get the whole cylinder assembly submerged in a thin penetrating oil or even kerosene. Let it sit for several weeks. Then attempt to drive the piston inwards to pull it out. You could alternatively heat the engine up real hot with several acetylene torches, cool the inside of the piston and use a grease gun to push the piston out of the engine. You must take some extreme caution as a grease gun can deliver 10,000psi of force. If it were smaller, I would suggest submerging the cylinder in an ultrasonic cleaner and just let it run. I have effortlessly removed very stuck pistons from two cycle chainsaw sized engines in this manner.

Chris
 

Scotty 2

Registered
Hello all
Some great ideas here but filling with anything is out as it's a 2 stroke. You can pour it in the top and it'll run out the ports in the cylinder.
I don't want to do the heat the outside and cool the inside trick at this stage as the cylinder has had frost damage and I don't to risk further damage. To make it worse, the damage is on the top of the cylinder so I have to be careful about trying to get the piston in a bit.
I'll have to be careful with this extraction. The chances of getting another cylinder or piston would be difficult over here.
I've been heating the cylinder up to give a few whacks and before it cools down I've been squirting oil in. Hopefully it'll creep into places where it hasn't over the last few years of just squirting oil into it.
At one stage I was even squirting synthetic AT fluid into it. Lucky I have mates with Allison autos :D

Cheers and thanks
Scott
 

cobbadog

Registered
Try your molasses and water or even your electrolysis tank as well Scotty. Or keep soaking it in anything you can get your hands on. Possible issues are either a stuck ring or the piston has grown into the bore and requires a lot of soaking. If it is a stuck ring you will have to get the piston to move in first before it comes out.
Nice to catch up on the phone today mate, nearly all packed and ready to go.
 

AussieIron

Subscriber
Last Subscription Date
02/04/2020
I agree with Cobbadog, might be simplest to give electrolysis bath but using caustic soda in solution. Putting the electrode on the con rod or piston might make a few more "bubbles" between piston and bore. The caustic may just work it's way in a bit more . I use caustic for electrolysis all the time on really dirty stuff, no damage to cast or steel. Just have it outside and be careful with it. Hot water in the solution makes it really go! Again be careful!
 

Mick

Subscriber
Last Subscription Date
07/12/2019
Make up a thick plate to bolt to the end of the rod in place of the cap and thread it to suit the shaft on a slide hammer and jerk it out that way. I just did a lister h like that and it worked great!
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
On an old 2 stroke, yanking or beating on a bronze rod might not be a good idea. On some pistons, the bosses on the piston itself may not take pulling, as the usual force is down from the top, not pull from the bottom! On some of these engines, using pressurized grease may end up breaking up the combustion chamber into the water jacket, especially if there is rust damage there already. The engine did ot get stuck in a day, it wont get freed up in one either. Time and patience, and a good penetrating solution will be your answer. in my experiance, a bigger hammer just breaks parts! Also, just heating the outside of the water jacket wont work. You need to heat the piston and cylinder, not the outside of the engine.
 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
I don't have much faith in penetrating oil in this situation. I had a stuck engine I filled with Kroil, let it soak for over a year, brought it in to the shop and it was still stuck, put air shop pressure in the plug hole for a week, still stuck. Removed the cylinder, pressed it in, pulled it out, the sides of the piston had dry powdery rust on them, no penetration. This engine wasn't stuck bad, I was able to clean the bores and pistons, good compression, runs fine.
 

Scotty 2

Registered
Thanks again all.

I've pretty well made up my mind to make a cradle to support the cylinder upside down (plenty of bolt holes on the cylinder) and a hardwood 'packer' so I can heat the cylinder and give the bottom of the piston a bit of a tap penalty to see if that makes any difference.
The electrolysis tank will be a try if the heat and tap doesn't work. After that another heat and drown in auto fluid and let sit for a few weeks and try again will be another approach.
In no hurry to get the piston out. Last stuck one took 18 months.

I had your method in my tiny mind Mick. At the moment the cylinder is loose with a couple of packers between the cylinder and base and I've been heating things up and pulling the flywheels over to do the hammering. I haven't really given them a great shunt. I really don't want to break something. It'll be hard (not impossible) to do the plate on the bottom of the conrod. This conrod has a pivoting side to it like a farm pumper, not 2 bolts.

You can see the frost damage repairs in the picture. I'm not game to put much pressure at all on them.

Cheers Scott

 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
If you have some Babbitt melt it in a pan and set the cylinder in it, you have a fitted cradle to press against.
 

Scotty 2

Registered
If you have some Babbitt melt it in a pan and set the cylinder in it, you have a fitted cradle to press against.
Now that's an idea. No fishing for awhile so a few KG's of the sinkers might just get melted in a big pot. A simple plug of the spark plug hole, drop the cylinder in, let cool and Bob's your Aunty.
What a champ!
If/when I get to that stage I won't use the press. I'll make the hardwood drift to fit the bottom of the piston and a hollow adapter to fit around the conrod and sit on the boss and use the little jackhammer. It seems to me that sudden impacts work better then continual brute force.
It's a bit like the mother-in-law continual nagging at me to fix the side gate. I usually fix what-ever it is just to stop the nagging.
Mrs Scotty just tells me once. If it's not done she doesn't feed me so that works too. Why did I write that? I don't know. The constant nagging is like a pile driver to my head I suppose. :bonk:

Cheers Scott
 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
When I put them in the press I apply all the pressure I'm comfortable with, if nothing moves I get the torch and start playing heat around the cylinder, through the water jackets. Usually you will here a thump pretty quik. When heating under the pressure of the press the piston will have a chance to move as soon as the cylinder expands, before the piston catches up with it.
 

I like oldstuff

Registered
Last Subscription Date
11/09/2015
When I put them in the press I apply all the pressure I'm comfortable with, if nothing moves I get the torch and start playing heat around the cylinder, through the water jackets. Usually you will here a thump pretty quik. When heating under the pressure of the press the piston will have a chance to move as soon as the cylinder expands, before the piston catches up with it.
Very true. Same with rusted in bearings in housings that are originally a press fit. In the press they go, heat the housing and you'll get a bang when they move. Then nothing. Cool it all down and repeat the process many times.

This cylinder with the non removable head and water jackets might be a very difficult push.
 
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