Freeing seized pistons

A pictorial example of the forces in play when striking a piston, to hopefully demonstrate why it is fine as long as your piston is not fully at TDC or BDC.
As well as demonstrating the need to separate the crank and conrod if it is at TDC or BDC.

more text to follow if needed

If you free the barrel from the crankcase you can put wood blocks between the barrel and crankcase when you get near BDC to save removing the conrod from the crank .......which you may not be able to get to anyway.

Just keep inserting bigger blocks each time you get near BDC until the piston comes out of the barrel.

That's how I got my Petter A1 apart

make sure the blocks don't raise it too near TDC

hob wrote:If you free the barrel from the crankcase you can put wood blocks between the barrel and crankcase when you get near BDC to save removing the conrod from the crank .......which you may not be able to get to anyway.

Just keep inserting bigger blocks each time you get near BDC until the piston comes out of the barrel.

That's how I got my Petter A1 apart

yep, that works well, wanted to put this up to show why its important as it came up recently

Andy, thanks for taking the time to do the explanation of the best way to remove a piston I'm sure it will be very helpful to others.

Stu.

stationary stu wrote:Andy, thanks for taking the time to do the explanation of the best way to remove a piston I'm sure it will be very helpful to others.

Stu.

not a prob, i hope it is helpfull, does the diagram get the point accross ok? will add some text later.

It does to me Andy but I understand what your talking about, you'd need to ask someone new that's doing this job for the first time to see if it's helpful to them. I'm sure if anyone doesn't understand they can just ask a question or 2 to get a better idea what your explaining.

Stu.

stationary stu wrote:It does to me Andy but I understand what your talking about, you'd need to ask someone new that's doing this job for the first time to see if it's helpful to them. I'm sure if anyone doesn't understand they can just ask a question or 2 to get a better idea what your explaining.

Stu.

fair enough lol, I did ask the wife, big mistake!

blackvanman wrote:fair enough lol, I did ask the wife, big mistake!

Andy, have you a death wish

Stu.

Just one thing I would add, the block of wood needs to be a good fit in the bore, otherwise you could end up with a piston crown like Nuts had in his Kohler! If the piston is crowned, like in a D type, you need to hollow out the centre so that the wood block rests on the outer edge, the strongest part of the crown. 2 Stroke pistons can be a real challenge.

Stamford24 wrote:Just one thing I would add, the block of wood needs to be a good fit in the bore, otherwise you could end up with a piston crown like Nuts had in his Kohler! If the piston is crowned, like in a D type, you need to hollow out the centre so that the wood block rests on the outer edge, the strongest part of the crown. 2 Stroke pistons can be a real challenge.

Very true you need the biggest bit of wood (preferably hard wood) you can fit into the bore to spead the weight or strike force. Also plenty of soakings with releasing fluid to help.
I've often thought about making up some kind of press to help remove pistons. You'll need a solid table with an engine on it or anything very heavy LOL. then under the table put your engine with the block of wood in then a car jack and jack against the weight of the engine on the table. I know it's something I was thinking of so it might or might not work. I'm lucky to have a steel bench that will take the weight of an engine or two no problem.

Stu.