ES2 stuck head

Worth trying kicking it over with the plug in (lead off!) and see if that will free it?
Otherwise heat from a heat gun can be your friend.
Good luck, 
George 

... people setting it at BDC, feeding a length of rope into the combustion chamber then rotating the engine and pushing the head off. Sounds  bit unlikely to me but people swear they've done it. Wouldn't do any harm anywayespecially if the rockers are off so valves closed.

Can you whack a wooden drift up against the exhaust port?

If you enjoy excitement..replace head bolts.  Slacken them back 1/16".  And fire it up! Problem might be stopping it if you have a magneto...?

...was how I got Doris's head unstuck.

No external violence required!

Hi John,

   All the methods of string and compression will only work if you have a bolted flange barrel, so not feasible in your case. Michael's advice is best using a piece of wood and hammer in both ports alternatively, but you need a friend to hold the barrel down. Also try tapping the head in a rotational direction as the barrel studs will stop the barrel turning. Whatever you do, do NOT try a tyre lever between the fins, I have lost count of how many broken barrel/head fins I've seen where this has been done.
   When you do get it stripped down, double grind the head and barrel joint and don't fit a head gasket.

The instructions are to use coarse grinding paste on the broad surface and fine on the spigot.  Then when it is cleaned off there will be a slight gap on the broad surfaces when the head is back in place, and the spigot will be in close contact.  There is no reason to desire or expect a smooth grey surface on the broad face.

Why use a sealant?  It's not specified or required.  You have already found the problems they can so easily cause.  And when and if you ever remove it again, you'll have the same problem.  There are no water galleries to worry about, and the assembly is so symmetrical that a sealant isn't necessary.

Some sealant might help around oil drain holes.  Some fit O rings there.

Can some ES2 experts assist?  As far as I remember, prewar bikes had no oil return galleries, but post war ones do have them - on the broad face.  So they must need an o ring?  Is that one reason why postwar OHV singles had gaskets?

Hi John
A few years ago on my M50 Mike Pemberton did my engine for me and we decided to remove the head gasket, so he machined a shallow area round the drainage holes in the barrel to enable some small 'O' rings to be fitted, and then ground them in, as previously suggested by David.
No sealant was used, or required for 20k hard miles until I got a slight weep from one of the 'O' rings. I have since replaced them with some Viton ones, and this time re-used a head gasket, for another reason than a leak.
Regards John O

Hi John,

   Looking at your photo, I can see this is a 350 head opened up for a over-bored 500 barrel. As David says you should use the fine past on the spigot joint as this is where the gas tight seal is required to be perfect. The coarse paste will give a very small gap on the outer area which is correct for a gas tight spigot joint. By using an aluminium head gasket you immediately nullify this seal by making a corresponding gap in the spigot, just where you need the perfect seal. Also, the gasket is too malleable and as the castings expand with heat the gasket can be squeezed out of shape and fail. Sealant should be used on the outer faces to seal the oil drain holes, with or with-out "O" rings. If you want to check the quality of the "O" rings, put them in some new engine oil and leave them in you domestic oven at 200c for an hour.

Hi David,

   Yes you are correct that no pre 1948 OHV engines had positive rocker lubrication as they were only oil mist lubricated. Pre-war these engines didn't use head gaskets and were a ground fit. This was a time consuming task and the use of gaskets later was to save money and speed up production. Just anecdotally, I have run this type of engine at up to 12.5 to 1 compression ratio, without a gasket of course!

Hi John,

   Looking at your photo, the spigot joint was not making contact around the full circumference area. I think this should be a priority as the holes for the head bolts are much too close to the edge, due to the larger bore, leaving hardly any margin to seal the outer area with a gasket. 
   Parallel twins with spigots should be machined so the gasket is a crush fit so the spigot will contact the head. On the Triumph Grand Prix engine, works machines cylinder heads were cut in half and ground in individually to the aluminium barrel.
   When Bert Hopwood redesigned the ES2/18 engines for 1948, these were fitted with head gaskets to speed up production as the accuracy of the machining was not spot-on and the gasket avoided the need to grind the joint by hand. This adversely affects the combustion as there is the gap where the top of the spigot is and this puts the onus on the outer face to take the combustion pressure. This is a poor, but cheap and easy, way to seal the joint.
   A good book to have is "Tuning for Speed" by Phil Irving, which gives much advice for best practice in engine building.

Does the engine have M Pem stamped on the side by any chance?!