Sprocket extraction

Have you used penetrating oil first? The puller screw lubricated? Could help a bit. Don't know if it is like swearing in church, but when the puller is tightened as much as you can,a hefty hammer blow on the end of puller screw usually loosen the sprocket. The shockwave helps overcome the static friction.

The sprocket can be super tight,  The best puller to do the job is an orriginal Bracebridge St one , RGM have some , Not a new type  they are useless.  Not easy to spot on the webbsite, not dear, get one.  Heavy solid and small 2  leg ,also usefull to pull main bearing off crank. Grease nose do up firm and clout with hammer. Heat can help. If I can find the ref no I will post.

Under primary area    .tools   item067500  £22  plus del, vat etc.  Not in general tools !!.  Likely to fly off with a BANG !! ,  be ready for that.   Duck.

Mine was a terrible job. Some have reported leaving a puller on overnight and coming down in the morning and finding it on the flow with a lump knocked out of the brick wall of his garage.

Slacken the nut one or two turns before applying the puller. Do not remove. That way the sprocket & puller can't fly too far when it lets go.

Thats the nuts !, why didn't I think of that ?.   far too simple.

... putting a mild steel spacer on the end of the crank to avoid burring the centre on the shaft. Brass is a bit soft as the puller needs to be done up tight as said.

When you use the puller spend some extra time to ensure the jaws get right into the sprocket and put a cable tie or big  worm clamp round it.

Hi Roger,  The alternator stator housing is fixed to the engine with 3  (if I remember !)  allen head countersunk set screws , With the correct ( whitworth  !) key they usually come out ok. The housing may be stuck to the engine case with some sealant,  which could be anything ,possibly something wrong    no nails ? !!  The primary inner case is also screwed to the engine  with a paper gasket and possibly more gooooooo-------.