If your eye is to bigg make some outside weldings, it will srink the eye.

I think the twinpipe was just show, it had to give the impresion of more speed.

In the first "The motorcycle"of March 31st. 1903 there are "motorcycle monstrosities", among them a clement V4 overheadvalve, weight 2 ctw. 0 gr. 13 lbs.
so this was build in 1902.

Yes it would, don't drill them all the way, stop at the tube.

You have mentioned the best way already, a copper gasked around the ridge is the savest, becouse if it's on the ridge there is a chance you will crack the head.
This is wy 50% of the 4 valve heads are cracked.

If you are using a gasket that's to soft you bent the carb. housing giving similar problems.

I have the engine plates for you, I had a 1955 engine but that went to France 6 month's ago.
Can bring to the rally to.

Some use pistons of a Caterpillar starting engine, wich is a English petrol engine to start up the big diesel.
I understand that they are still in stock.

The hunter had the quick turning throtle lever in 1936, the low barrel is 250 or 350 but the front mudguard seems hunter. On this photo it would be 5 years old, that would fit the shiny clutchdek. You can see it better on; nederlandsearielclub.nl - forum - algemeen. The number could be DDE22 or DOE22.

This is a Dutch man called Koos, who was during 1940-41 in England on a English Ariel.

Koos famely wants to know;
wat type of Ariel is it ?.
dus it still exist ?.

The parts the man where selling seem to be from a restored motorcycle, so maybe its good that you didn't buy it.