Freeing Stuck Piston
Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo
- Jerry In Maine
- Posts: 140
- Joined: Thu Aug 12, 2010 3:19 am
- Location: Surry, Maine USA
Freeing Stuck Piston
at the moment i have a 40+ cylinder containing a very, very stuck piston. its soaking in a slow cooker set on high (which gives about 275*F) filled with a 50/50 mix of 5W20 oil and brake fluid. I'll let it cook for a few days then hopefully i'll be able to knock the piston out with a hammer and a wood drift.
curious as to what others have tried?
curious as to what others have tried?
Last edited by Jerry In Maine on Wed Sep 15, 2010 11:54 pm, edited 1 time in total.
-
- Posts: 2838
- Joined: Thu Aug 07, 2008 8:42 pm
- Location: Surrey
Re: Freeing Stuck Piston
I use thermal shock and WD40.
Some people say leave it for months in oil but I am not that patient.
Get it hot, but warm the whole thing evenly so that you do not crack the cast iron.
With the head and the crankcase removed you can then knock the piston out with a wooden drift.
A 102 is a little more tricky.
H-A
Some people say leave it for months in oil but I am not that patient.
Get it hot, but warm the whole thing evenly so that you do not crack the cast iron.
With the head and the crankcase removed you can then knock the piston out with a wooden drift.
A 102 is a little more tricky.
H-A
- 40TPI
- Posts: 451
- Joined: Fri Jan 26, 2007 7:08 pm
- Location: North Buckinghamshire, 110 miles south of Yorkshire, England.
Re: Freeing Stuck Piston
As I said a week or so ago I failed miserably with a wooden drift preceded by 15 months of diesel soak and a poor man upper cylinder hydraulic cook off heating a full bore of cold diesel with the plug replaced............
http://www.saving-old-seagulls.co.uk/fo ... 861#p12861
Now moved over to a couple of 57mm -15 thou in diameter x 6mm thick ali discs, ( hard, probably in T6 condition) in conjunction with a 150mm length of ali scaffold pole. I'm sold on the idea. Huge success!!!! In fact done two total basket cases this week. The piston in that pic is now out without a hole in the top from a drift. In fact one of the two rings also survived and will be refitted. As promised I will put the pics up after I get some sleep. (I'm just so knackered having worked a couple of consecutive ghosters on the rope walk at Chatham laying up tow warps for Woodman to use at Cholsey this weekend.............)
Peter
http://www.saving-old-seagulls.co.uk/fo ... 861#p12861
Now moved over to a couple of 57mm -15 thou in diameter x 6mm thick ali discs, ( hard, probably in T6 condition) in conjunction with a 150mm length of ali scaffold pole. I'm sold on the idea. Huge success!!!! In fact done two total basket cases this week. The piston in that pic is now out without a hole in the top from a drift. In fact one of the two rings also survived and will be refitted. As promised I will put the pics up after I get some sleep. (I'm just so knackered having worked a couple of consecutive ghosters on the rope walk at Chatham laying up tow warps for Woodman to use at Cholsey this weekend.............)
Peter
- Jerry In Maine
- Posts: 140
- Joined: Thu Aug 12, 2010 3:19 am
- Location: Surry, Maine USA
Re: Freeing Stuck Piston
a mechanic told me of how he welds a grease fitting to the base of a spark plug and then pumps the cylinder full of grease. apparently a common grease gun can create very high pressures - often enough to free the piston. thing is though the piston can come out of the cylinder at considerable force slinging grease everywhere so it's best to keep a cloth around the entire assembly until it lets go. As I understand this'll only work if the intake/exhaust ports are not exposed. Seems to me that you could warp the head from all the pressure if the piston was really stuck hard.
wish I had a hydraulic press. trying to homebrew one up using a hydraulic jack and some thick iron. I think that letting it soak in hot oil for a few days then applying steady pressure with a press might do the job quicker. One thing about the hot oil soak: it sure cleans out the cooling water passages. If I ever do get the piston out I'll have a motor that cools well.
I wonder: is the majority of the cause of the sticking due to the iron rings rusting to the cylinder walls or corrosion of the aluminum just getting in the way? Maybe it depends on the conditions in which the motor was stored...
I'll get the damned thing out...one way or another, she's coming out.
wish I had a hydraulic press. trying to homebrew one up using a hydraulic jack and some thick iron. I think that letting it soak in hot oil for a few days then applying steady pressure with a press might do the job quicker. One thing about the hot oil soak: it sure cleans out the cooling water passages. If I ever do get the piston out I'll have a motor that cools well.
I wonder: is the majority of the cause of the sticking due to the iron rings rusting to the cylinder walls or corrosion of the aluminum just getting in the way? Maybe it depends on the conditions in which the motor was stored...
I'll get the damned thing out...one way or another, she's coming out.

- 40TPI
- Posts: 451
- Joined: Fri Jan 26, 2007 7:08 pm
- Location: North Buckinghamshire, 110 miles south of Yorkshire, England.
Re: Freeing Stuck Piston
Jerry In Maine wrote: thing is though the piston can come out of the cylinder at considerable force slinging grease everywhere so it's best to keep a cloth around the entire assembly until it lets go. As I understand this'll only work if the intake/exhaust ports are not exposed. Seems to me that you could warp the head from all the pressure if the piston was really stuck hard.
Unlike air oil/grease don't compress. It won't cause a deluge! Any egress will be limited to the exhaust and transfer ports since the piston will stop as soon as they start to open. Pumping more grease in will only fill up the ports.... It will not push the piston all the way out.......and certainly not as a projectile! Hope fully having started to move it you will be able to complete it from above with a wooden drift........
Peter
Last edited by 40TPI on Sat Sep 18, 2010 1:30 am, edited 1 time in total.
- Jerry In Maine
- Posts: 140
- Joined: Thu Aug 12, 2010 3:19 am
- Location: Surry, Maine USA
Re: Freeing Stuck Piston
i guess you're right. the fellow who explained it to me was an auto mechanic and works on 4 strokers so they wouldn't have the ports in the cylinder to allow the grease to escape prior to the piston popping out.
at any rate i just got my piston loose! it took 2 days simmering in the magic potion to loosen it up though.
at any rate i just got my piston loose! it took 2 days simmering in the magic potion to loosen it up though.
Re: Freeing Stuck Piston
Sounds fun here. A few months ago I was in this position, piston stuck tighter than a duck's a..e! A month, well 3 weeks to be precise, soaking in deisel oil then a tap with a wooden bung and she slipped out like ..........a duck's a..e in motion! I'm sure you'll get it out but try some patience with whatever method you choose, it'll be worth it if it comes out in one piece, unwarped.
Good luck.
Gerard
Good luck.
Gerard

Re: Freeing Stuck Piston
Hi all - just registered to this forum. I was about to buy a new Yamaha two stroke 3 HP outboard for my inflatable to use as a yacht tender when a friend advised me that he had an unused Seagull outboard circa 1985 that I could have for nothing. I just picked it up - what a piece of engineering. Looks funky, in great nick as far as I can see but, and there is always a 'but', the engine is seized. I removed the spark plug and there appears to be some minor corrosion around the piston and cylinder walls.
I guess I will have to pull it apart and rebuild it. Is this a job for a handy guy who is not a mechanic? Where can I get a shop manual? Given that there is no evidence of any significant corrosion on the exterior is this likely to be difficult?
And finally, will it be worth the effort or should I give it back and buy the Yamaha? The serial number is ED104AA3, purchased new in 1985 for $A395.
I guess I will have to pull it apart and rebuild it. Is this a job for a handy guy who is not a mechanic? Where can I get a shop manual? Given that there is no evidence of any significant corrosion on the exterior is this likely to be difficult?
And finally, will it be worth the effort or should I give it back and buy the Yamaha? The serial number is ED104AA3, purchased new in 1985 for $A395.
Re: Freeing Stuck Piston
You have a 102, made January 1973.
If you click on the SOS logo at the top of the page you will find most, if not all the information you need.
And yes its always worth restoring a seagull.
If you click on the SOS logo at the top of the page you will find most, if not all the information you need.
And yes its always worth restoring a seagull.
- Charles uk
- Posts: 4972
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Freeing Stuck Piston
Inputting your engine to the Seagull identifer will bring up another jinx.
Electronic ignitions first appeared in 1979, so ED104AA3 should be a long waterjacket, short shaft, 102 with electronic ignition & and an Amal 416 carb, can't be 1973, ought to be 1993, if the engine number is correct.
I wasn't aware that 102's were made in 93 but it's quite possible as a special order, to find out what it really is we need to see pictures, I'm sure section 33 will tell you how to do this.
Both sides of powerhead, gearbox & prop, fuel tank logo & a couple of the whole thing.
This is a very unusual 102, not very many of these were made, I've only seen 1 & John a couple, quite a desireable model, If your going to biff it, biff it in my direction.
Well worth the work, start reading all the threads that relate.
Electronic ignitions first appeared in 1979, so ED104AA3 should be a long waterjacket, short shaft, 102 with electronic ignition & and an Amal 416 carb, can't be 1973, ought to be 1993, if the engine number is correct.
I wasn't aware that 102's were made in 93 but it's quite possible as a special order, to find out what it really is we need to see pictures, I'm sure section 33 will tell you how to do this.
Both sides of powerhead, gearbox & prop, fuel tank logo & a couple of the whole thing.
This is a very unusual 102, not very many of these were made, I've only seen 1 & John a couple, quite a desireable model, If your going to biff it, biff it in my direction.
Well worth the work, start reading all the threads that relate.
Make it idiot proof and someone will make a better idiot.
- Jerry In Maine
- Posts: 140
- Joined: Thu Aug 12, 2010 3:19 am
- Location: Surry, Maine USA
Re: Freeing Stuck Piston
biffCharles uk wrote:...quite a desireable model, If your going to biff it, biff it in my direction.
there's yet another word i gotta look up at http://www.translatebritish.com/index.php along with some others i've found here like duff, dodgy, bodge and knackered!

- Charles uk
- Posts: 4972
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Freeing Stuck Piston
For you colonials we try to use some slang as we are fully aware that the "Queens English" is not your first language.
Make it idiot proof and someone will make a better idiot.
Re: Freeing Stuck Piston
Firstly it depends how badly the piston is stuck. If you have been given a motor that has been-under in the sea then left in someone's back garden in the rain for ten years you will have a big problem. Secondly it depends on what tools you have or have access to. The problem with hitting the piston from the top is that its not flat, in any case one is liable to cave-in the crown. Here is another approach. With the cylinder barrel removed from the motor and the crankshaft removed one has access to the underside of the piston. The trouble is that there is nowhere good to hit it. What one needs is about three inches of thick walled steel tube and a friend with a lathe. Scaffold pipe is about the right size. Before machining the pipe make sure that the end of it hasn't been belled-out by some previous persons hammering. If it is bell mouthed or burred it will never run true (guess how I found out) Machine the pipe until it is a slip fit in the cylinder bore, only about an inch needs to be machined as once the piston moves it should be possible to drift it with wood. Face off the tube end square, de burr and polish with emery paper, glass paper or whatever is handy. The tube can now be used to apply force on the piston skirt. I used a large G clamp and steel plates. At the top of the cylinder I let the spigot press against wood. I have sprayed it with releasing fluid for days, I have heated it with a blow=lamp whilst under pressure and have hit it with a hammer but so far nothing has worked. Although aluminium has a different expansion rate when compared to cast iron, heating and cooling has no effect. The problem is the piston rings and I feel sure that it is rusted rings that are holding it. Next try will be a second G clamp. I do have a fly-press but I doubt whether there is sufficient height. Another way is to use a hydraulic jack but one needs to make a sturdy frame to turn a jack into a press. A friend works at a place with a hydraulic press so now that the tube is made he might be able to do the job for me.
If anyone knows how many tons these cylinders will stand I'd be glad to know.
If anyone knows how many tons these cylinders will stand I'd be glad to know.
Re: Freeing Stuck Piston
Firstly it depends how badly the piston is stuck. If you have been given a motor that has been-under in the sea then left in someone's back garden in the rain for ten years you will have a big problem. Secondly it depends on what tools you have or have access to. The problem with hitting the piston from the top is that its not flat, in any case one is liable to cave-in the crown. Here is another approach. With the cylinder barrel removed from the motor and the crankshaft removed one has access to the underside of the piston. The trouble is that there is nowhere good to hit it. What one needs is about three inches of thick walled steel tube and a friend with a lathe. Scaffold pipe is about the right size. Before machining the pipe make sure that the end of it hasn't been belled-out by some previous persons hammering. If it is bell mouthed or burred it will never run true (guess how I found out) Machine the pipe until it is a slip fit in the cylinder bore, only about an inch needs to be machined as once the piston moves it should be possible to drift it with wood. Face off the tube end square, de burr and polish with emery paper, glass paper or whatever is handy. The tube can now be used to apply force on the piston skirt. I used a large G clamp and steel plates. At the top of the cylinder I let the spigot press against wood. I have sprayed it with releasing fluid for days, I have heated it with a blow=lamp whilst under pressure and have hit it with a hammer but so far nothing has worked. Although aluminium has a different expansion rate when compared to cast iron, heating and cooling has no effect. The problem is the piston rings and I feel sure that it is rusted rings that are holding it. Next try will be a second G clamp. I do have a fly-press but I doubt whether there is sufficient height. Another way is to use a hydraulic jack but one needs to make a sturdy frame to turn a jack into a press. A friend works at a place with a hydraulic press so now that the tube is made he might be able to do the job for me.
If anyone knows how many tons these cylinders will stand I'd be glad to know.
If anyone knows how many tons these cylinders will stand I'd be glad to know.
Re: Freeing Stuck Piston
The piston and cylinder were left overnight with the G clamp pressure still on. Another dose of maintenance spray was given before going to bed. In the morning the pipe was given another blow from a hammer but surprisingly the tone had now changed. Instead of a steely note and the hammer doing a ricochet there was more of a dull thud. Looking in through the exhaust port showed that the piston had moved! With more hammering, more tightening of the G clamp and more spray out it came! A power driven wire brush was then used and the piston cleaned up a treat, even the rings are still OK! The cylinder is good too! 
