3 start and 6 start oil pumps ?

count the number of 'starts' on the worm drive (crank) gear.  No need to remove the gear from the crank. Look on the AN site at the commando crank worm gear (6 start) to get an idea of what you are looking at.

oil pump gear has a right hand thread. The crank worm drive gear is left hand

Wayne,

I just wonder if the above is clear enough for a newbie to Norton.

To remove the oil pump it is usually sufficient to remove the two nuts on the two fixing studs. Just lift the pump off the studs complete with the pump drive gear. 

The nut holding the drive gear is a normal right hand. The pump gear is keyed to the pump shaft. 

You can hold the pump gear with soft jaws, with care, while undoing the nut. The gear can sometimes be reluctant to slide off the shaft and key.

No need to undo the crankshaft mounted worm drive gear, which is a left hand thread. Very shallow hexagon on this which is best tackled (if you need to at a future date) with the proper socket, ground back about 1mm to get rid of any entry radius on the socket.

All your questions are well covered in the Norton Twin Cylinder Manual, with diagrams. I recommend it. Readily available.

Peter

You must also use a 6 start worm with a 6 start worm gear. 

you have joined the large group that discover the term ‘rebuilt’ could mean almost anything…..!

   it’s all part of the learning process.

If i were  rebuilding a dommy now I would consider buying a used 650 pump ,recondition  it, Fit with the Dommy 3 start gear set . This will give a slightly better oil supply. Fit a calibrated restrictor in the tank return union to improve the valve gear supply and be prepared to adjust the size  of restriction. to get the result wanted. Fit better oil control rings to pistons .