hi,whoever this motor belongs to,you are now flogging a dead horse,the piston is at practically top dead centre,all your hammering,or someones hammering,is only battering your big end
bearing,not moving the piston,the peening action has now spread the piston even tighter in the bore.
this is a worst case scenario for a siezed or rusted motor,when the crown of the piston eventually breaks free you will be no further on and have less to bash at.
i would suggest a blowlamp or similar heating device,not oxy aceteyline.
warm the barrel,evenly,all round,this will not damage the barrel,it may break the bond,good luck,cheers rick

email (option): richardholt@rocketmail.com

Hi Rick,

I bought this engine some 2 years ago, after it stood in a leaking shed for some 40 years with no spark plug.

The price was not cheap, as it was a “green” army engine with a re-condition tag,
And I was promised that it would “most likely” free easily.

I opened the head and put in all kind of oils and thin lubricant, then submerged it in kerosene for few months-
Nothing helped.

I heated the barrel with Brenner, put it in fire- nothing.
The only option I had to save the barrel, which is a standard size and has good fins was to drill around the piston.

I lost the piston and would not trust the conrod, but have a clean good barrel to rebore to +20,
And the bottom case.
(Well, to be honest- the bottom also suffered water damages, but case is ok, fly-wheel, screws, bolts, few other useable parts)

I admit now that I was too keen to get this motor, and as mentioned paid good money for it,
But I am not in England or Europe, and parts are getting very hard to obtain here, and very very expensive to import, as most are very heavy.

After this one, I found and bought another engine which was clean and nice.
I totally restored it with all NOS parts and enjoy it now on my bike.


Noam.

email (option): noam10@gmail.com